Carbon Clinchers—Are They Ready for Prime Time?

Last February the guys who promote Levi’s Gran Fondo, Bike Monkey, issued a press release asking riders to leave their carbon clinchers at home. The ride takes in a fair amount of descending and some of the roads riders drop down are simultaneously steep and twisty. It’s not a great combination for riders who may not have a lot of experience and/or confidence on descents. One road in particular, Meyer’s Grade, hits 18 percent, but of course does that in a stretch followed by a slightly off-camber left.

In my personal experience, I’ve gone as fast as 44 in that section. A friend of mine did 54 there.

When Bike Monkey issued the release, I took some note of it, but knowing that their first interest is to prevent injury and give entrants the best, most successful experience possible, I didn’t blame them. For some years I’ve been seeing carbon clinchers fail in the Santa Monica Mountains. The descents that bring riders down to Pacific Coast Highway drop, on average, 2000 feet and contain an either terrific or terrifying mix (depending on your view) of steep drops and frequent turns.

Frequent readers of RKP have heard me sing the praises of these roads in Malibu. They are the most challenging descents I’ve ridden anywhere, including the roads used in Levi’s Gran Fondo.

Epic Fail
I’ve seen a fair number of carbon clincher failures. We’re talking melted brake tracks, flat tires, wives called for rides home. I’ve contemplated a post on whether carbon clinchers were really a product that was as safe and reliable as aluminum clinchers. My concern was that it was unnecessarily argumentative, that I’d be picking a fight where none was required.

Just more than four months have passed since Bike Monkey issued that press release. It seemed that a well-intentioned advisory would go unnoticed by the industry, which was just as well. Then I got this from Reynolds Cycling:

June, 28, 2012 


West Jordan, UT – There’s generally a fair amount of concern about the safety of carbon clincher wheels failing or “exploding” when braking under extreme conditions. Recently a major Gran Fondo has warned against the use of full carbon clinchers in its event. There
has also been recent press raising more questions among cyclists in regards to the safety of carbon fiber clinchers.

CTg Brake Track
CTg Brake Track 

At Reynolds Cycling, safety is our
FIRST priority and we have gone to great lengths to ensure that all our wheels offer optimal braking, and
are safe for riders.


We spend countless hours developing and testing wheel designs and wheels before moving to final production in our private owned manufacturing facility. We choose only the highest quality materials from Mitsubishi and control our resin chemistries to produce the highest quality of carbon fiber wheels for our customers to ride.


Once in production our wheels are hand molded using our CR6 technology. This process
utilizes 6 different types of carbon fiber per rim. Each type is chosen for its attributes in weight, stiffness, quality consistency, and overall durability. These different lay-ups are
used in the nipple bed, tire channel, spoke face, rim hook bead, side wall and the
brake track.

Cryo-Blue Brake Pads
Cryo-Blue Brake Pads

Our braking technology
, known as CTg (Cryo-Glass transition) has proven to be the best performing carbon braking system on the market. When paired with our proprietary Cryo-Blue brake pads, Reynolds’ rim temperatures are approximately 100 degrees (F) coolerthan our closest competitor. CTg runs so much cooler by using the innate energy conducting properties of carbon fiber. The material used in CTg disperses heat from the brake track into the rim. As the rim spins through the air, it naturally helps cool the material down. Overheating is the enemy of carbon fiber braking surfaces and can potentially lead to warping or failures. In regards to rims “exploding”, we’ve found through thorough testing that this phenomenon is directly related to a tube or tire failing to the point of bursting under extreme heat. The energy from this burst can cause a rim to crack or push out, but a carbon rim spontaneously exploding to the point of massive failure is highly unlikely.


When asked about the warning from the event, Paul Lew, Reynolds’ Director of Technology and Innovation, states, “Courses which are technical, particularly those with steep gradients and which involve large numbers of closely-grouped cyclists of varying abilities, create the high likelihood that cyclists will ride the brakes for prolonged periods of time. This is a recipe for trouble, regardless of the wheel or material. I think this is the reason that an event promoter would single out carbon clinchers. One could even relate the ruling against aero bars in group rides to this decision. It comes down to experience of the rider and control at higher speeds.”


We at Reynolds Cycling stand behind our product and the safety of our riders whether they be on the AG2R Professional Cycling Team, Kelly Williamson racing to a record bike split, the amateur racer looking to best their opponents on a local criterium course or even a group of cyclists getting together to ride for a great cause.


For more information on Reynolds Cycling wheels and our CTg braking technology

Forgetting for a moment that it took them four months to formulate a response, and that it mostly reads like marketing copy, Paul Lew’s rebuttal to the concern about carbon clinchers attributes the problem to a cluster of riders of varied abilities and that people are just riding their brakes too much.

Well, Paul, thanks for throwing the consumer under the bus.

Here’s a newsflash: The first rule of PR in any product failure is never to blame the consumer. This was a disappointing dismissal of a valid concern. I believe it deserves a response, so I reached out to friends that I ride with plus a couple of retailers to ask them what their experience has been. What I heard back wasn’t surprising given what I’d already seen. Friends and retailers reported failures of the brake track due to braking heat with the following manufacturers: Reynolds. Easton, Enve, Bontrager, Roval and Lightweight. This is but an anecdotal sampling, unscientific even, but it’s significant because the population it draws from are competent riders who are accustomed to the mountain roads above Malibu and earned their skills racing crits here in Southern California. They know how to corner; they know how to brake. I’ve got a family who depend on me, so I can say with some conviction, if these guys were buffoons, I wouldn’t keep riding with them.

In the case of Lightweight, Easton, Enve and Roval, there were very few reported failures. In the case of Roval, they were all first-generation wheels; I heard the second generation has been much better. Bontrager had double the rate of failure reported for the others. Reynolds had more than six times the rate of failure of brands like Lightweight. Now, I need to add a caveat here: Reynolds’ market penetration is superior to those other brands; I don’t believe it would be fair to say that the Eastons are six time as good a wheel as Reynolds, but what is troubling is that nearly everyone I talked to about Reynolds’ carbon clinchers reported that they had killed more than one set. Friends I talked to commended them for their excellent customer service (one friend who killed wheels from Reynolds, Easton and Bontrager said that Reynolds’ customer service was both the quickest and least expensive), so there’s that.

The Upshot
One needn’t be a timid descender to melt a carbon clincher on the canyon roads in Malibu. You don’t need to be following someone else who doesn’t know what they are doing, or riding your brakes because you’re behind a car.

I know this to be true because I melted a Reynolds Stratus rear wheel descending Las Flores road at the absolute limit of my ability. So badly did the brake track deteriorate in one section that I had to pull over and get the bike stopped so that I could open up the brake quick release and then loosen the barrel adjuster so the brake wouldn’t rub the wheel. And I wasn’t even finished with the descent. The steepest portion of the descent was yet to come; I was scared shitless until I reached PCH. Even then, things didn’t improve much as I still had to pedal 20—mostly flat—miles home.

It would be easy to accuse me of riding my brakes down that descent, that I was too timid to let the bike run and that’s why the wheel melted. Well, you can check out my times for descents like Tuna Canyon, Las Flores and Decker on Strava. You’ll see that I’m reasonably fast, fast enough to consider brakes counterproductive to a good time. When that wheel melted, I was not the problem.

The Exceptions
The retailers I spoke to noted that what they aren’t seeing returned are Enve’s new SES rims and Zipp’s Firecrest Carbon Clinchers. While I can’t speak to the new SES carbon clincher (I don’t even know anyone who owns a set), I can say that I’ve taken both the Firecrest 303s and 404s down Las Flores, and though at a certain point the brakes howled like a dog for a full moon, braking remained consistent and the wheels remain perfectly true.

I wouldn’t be responding like this had I not experienced a rather surreal meeting with Paul Lew at Press Camp. Now, I like Paul; we’ve spoken in the past and I think he’s a really cool guy with whom I share full geekage. But in our meeting, when I brought up the issue of carbon fiber clincher failures—broadly, I wasn’t even pointing a finger at Reynolds—he sidestepped the issue and began with a marketing pitch for how their new brake shoe shares a polymer with the resin they use in the brake track that lowers braking temperature by 100 degrees. When he knocked the Firecrest and SES designs and insisted that the RZR was a much faster wheel and I tried to ask about handling issues that Firecrest and SES address, he dodged that as well. After leaving the meeting I told a friend that I felt like I’d been told the sun rises in the west.

People of the bike industry—propaganda is for politics. If you want me to write about your products, you need to be prepared to have a candid conversation with me. If I feel I’m being fed a line of bull, I will be less inclined to call in the future.

I think that the guys at Bike Monkey made the right call. They don’t need me to have their back, nor do I have a vested interest in their success, but in the interest of disclosure, I’ll admit that I know them, like them and appreciate that they provide me with free entry to their events. And yes, I’ve even contributed to their magazine. They are good people who made a judicious call.

Here’s the bottom line for most consumers out there: Generally, carbon clinchers work really well. If you live in a flat or moderately hilly place, they’ll be perfectly fine. I’ll hazard a guess that were I still riding in the Berkshires of Western Massachusetts, I wouldn’t have a problem with them there, either. However, the Santa Monica Mountain provide the most technically demanding descents I’ve encountered. There are spots in Sonoma County that rival them, though. Wheels are failing on these roads. And the wheels that fail on these roads are carbon clinchers exclusively.

Finally, I’m issuing an invitation/challenge to the entire industry: If you make carbon clinchers and you think they are up to any challenge, come ride with me.



  1. George

    The evasion by the industry (while simultaneously trying to engineer around the problem) reminds me of how GM tried to blame engine fires in the Pontiac Fiero (ironically?) on drivers misusing the car – a car they had styled to look like a sports car but apparently had engineered to tolerate only driving to the train station and back and which rebelled against alternative usage by bursting into flames. That was apparently the consumer’s fault. And as you can expect, GM was ridiculed.

    You’d think there’d be somebody in the wheel industry old enough to remember that debacle.

  2. noel

    Mr Lew is welcome to make measure of my riding ability up and down. We can include the climb in the overall or he can just pick a canyon with me to descend. I’ll even wait for him. I bought in understanding that all materials have limits and outside of racing, where i stayed off brakes as much as possible… but also where i’ve had to ride them more than anywhere (neutral rollouts and oddities came up)…. i found my three sets of Reynolds to be amazing wheels. They’ve lasted longer than any wheelset i’ve ever owned and they’ve required less maintance. I love em. Hundreds of races on them and tens of thousands of dorking out miles.
    I’ve melted them a few times and was well serviced by Reynolds.. never a race failure. (Turbo is the best guy in the word to have working for you).
    Now that I’m not racing… the not having the option to do a soft descent on them… and the threat of occassional melt … is a hassle. Tuna and Las Flores can turn a rim into goo in a blink (on a hot day). All it takes is getting caught behind a car. Having it put on my riding ability rather than just a natural limitation of the material…. offends. It’s a turn off.
    I dont think anyone needs to apologize for limits. If you have to over-brake and its hot out… you can end up killing a rim. It is what it is. It’s also a normal experience if you live in an area that has steep technical climbs and hot weather. More than anything, its a mental stress… knowing you have to descend for the rim when you don’t feel like it. Ultimately, an informed consumer is as nice as an informed product rep. I like them… but we both have limits. I ride for fun…. its just stuff. They’d be perfect if there were no Tuna and Las Flores… but theres so many choices of wheels to pick. Who’s fault is that? (rhetorical first world problem). The attitude you reported doesn’t fit my experience with them… it makes me a little sad to read.

  3. Walt S

    Isn’t it interesting that the gullible cycling consumer is paying big bucks, $2,700 in the case of ZIPP FIRECREST WHEELS, to field test a product that is known to fail under extreme braking conditions? Under the wrong conditions, carbon clinchers fail. Period. Fact.

    For a 100 fewer grams, projected possible aerodynamics, and let us not forget the “cool” factor, cyclist are purchasing wheels that have a debatable safety and longevity record. In keeping with the car analogy and blaming the consumer rather than the product, remember the Ford Explorer and the tests that showed that the vehicle was inordinately top heavy and would tip over when violently swerving to avoid an accident? Carbon clinchers are only safe when we brake in non demanding conditions.

    That’s what I want to do. Spend my hard earned money on something that just might (will) disintegrate if I actually use it for its intended purpose; riding it as a bicycle component.

    1. Author

      TommieT: Thanks much.

      George: Great point. I had a similar conversation with my wife about Toyota.

      Noel: Thanks for joining the conversation. One of my concerns is that if a hot day can make the difference between getting down a descent safely or turning wheels to goo, then there isn’t a broad enough operating range for the rims. Ambient temperature shouldn’t make a difference.

      Walt S: Interesting that you chose to call out Zipp’s Firecrest wheels. I’ve done a lot of asking around and haven’t found anyone who has killed even a single wheel. I’ve got both the 303s and 404s and I’ve braked hard on them on the most difficult descents I know and haven’t killed any. That lead me to the conclusion that not all wheels are created equal. To say that carbon clinchers fail, period, just flat-out isn’t reflected in real-world experience. And calling cycling consumers gullible is an unwarranted insult.

  4. Jack Burton

    Walt S,

    I agree with most of your comment but you may have misread the article. The Firecrest wheels may have howled but they did not fail, and braking remained consistent. This has been my experience as well, they are some of the best braking, most consistent carbon wheels out there. Reynolds and others came to market with carbon clinchers years before Zipp did. Is it because Zipp didn’t have the ability to make a comparable carbon clincher? No, it was because Zipp chose to hold off releasing a carbon clincher until they could produce one that passed their tests (word on the street is that the only other rims that came close to passing the Zipp torture tests were Campy carbon clinchers).

    Anyway, I have seen Reynolds rims fail first hand and it is scary. To think that any brand would knowingly produce a product that is known to fail like this blows my mind. I would imagine that the Reynolds lawyers have their hands full… It is also beyond my understanding how some people are willing to ride this product after it failing repeatedly… great customer support doesn’t make up for a product that COULD FAIL AND KILL YOU ON A GNARLY DESCENT. wtf

  5. Randomactsofcycling

    I have been waiting an awfully long time for Carbon Clincher race wheels. I could never see the point of Tubulars, as I am not part of a team and don’t have a support car to help me when I puncture.
    I went within a whisker of buying carbon/alloy clinchers, despite the weight penalty. My LBS continues to refuse to endorse anything other than Campagnolo. Given his experience and the value of the advice he has given previously, I trust him. I want deep/medium
    Profile ‘aero’ wheels but what’s the word on Campy Hyperons?

  6. Cary Ford

    As a very timid descender and a big rider of brakes on most any descent, especially the more technical twisty ones in the Santa Monicas, including Las Flores, I have never once had an issue with my Campy Hyperon clinchers which are going on 6 years old now.

  7. Noel

    A different Noel here.

    I’m one of the causes for Bike Monkey’s press release. I rode carbon clinchers in the 2011 LGF and managed to melt the rear going down Meyer’s Grade. When the SRAM support car came by (and gave me an alloy brake track Zipp 404 to finish on), I saw several other destroyed carbon clinchers on the roof.

    I was really disappointed that the wheel was ruined. Several local shops were singing the praises of the wheels and were adamant that my weight (80kg) would pose no issues. I had even tried to wreck them going down Mt. Diablo and thought I was safe.

    The wheel was replaced under warranty and the set now has a new home. I’ll second the opinion that, carbon clinchers are great for flat to

  8. Doug Page

    I thank you for the insight, Padraig. I have zero experience with this kind of wheel, nor do I ride with guys who have them. I don’t have the money either, so it is kind of a moot point for me. I expect my wheels to last many years, again because I don’t have the means to buy the latest and greatest components every year or so. I don’t think I will ever buy carbon clinchers, until and unless I put them on a disc brake bike. I look forward to a future post where you let me know which disc brake systems can survive long descents without failure.

  9. Noel

    Make that flat to moderately hilly rides. Carbon clinchers aren’t good for long and/or super steep descents and don’t plan on stopping in the wet. I chose to go back to aluminum brake tracks because I just want to ride without having to make a conscious decision about the limits of my equipment.

  10. Joel

    Is the break track melting an issue with tubular carbon rims? Obviously there isn’t the issue of the bead blowing off the rim but it seems rim longevity would still be a problem if you rode in a mountainous region.

  11. DoubleUc

    So is one to think that the tubular( I prefer “sew-ups” ) type carbon rims to be any different?
    At first glance I can understand the actual depth of braking surface and/or material being completely contrary but I’m only assuming this fact to make a difference(?) in the durability aspect.

    However, the very topic has me on the fence of the purchase of said wheels to be a wise one.
    I have race “tested” a set of the older style 303’s and discovered, with the help of the rain,
    that the braking was completely sketchy as it would be with any carbon wheel when exposed to water. I do live in a local where there aren’t that many hills, much less mountains, but my riding style relies on hard braking when I find myself on the down side bombing a decent.

    Be that as it may, do you have any experience in reference to the “flat tire” in regards to the integrity of a carbon clincher. I can see a big problem with any carbon clincher but its only based on speculation. I also have concerns with the idea of putting many “training” miles on such expensive rims that already have “problems”. Are my worries worth any merit?

  12. Brian Lockhart

    As someone already responded – this problem goes away (or at least morphs) once hydraulic disc brakes arrive on high end road bicycles. Rim brake tracks become a thing of the past, and the discussion then turns to warped rotors, brake fluid, and pad compounds. 🙂

  13. thrash

    I am liking my ZIPP 101’s now more than ever. Spend over $2,000 and feel LESS safe on a technical descent? There is one particular decreasing radius off camber on Los Flores that we ALL know about. I want full brakes setting up for that corner.

  14. Ransom

    I don’t doubt that there is an issue with carbon clinchers, or doubt any of your findings.

    The only thing that strikes me as odd is the emphasis on riding the brakes or going slowly causing problems.

    It doesn’t come up as much in bicycles, but where you run into heat issues with cars and motorcycles is when you are carrying a lot of speed, and then need to brake aggressively. I.e. the sort of thing a skilled descender might do in coming down a steep pitch prior to an off-camber corner, where a less experienced cyclist might try to keep the speed checked to something less intimidating all the way down.

    I’m just curious because there was so much emphasis on riding the brakes being the cause, and the victims’ skill making this unlikely, which in turn places their approach to braking in exactly the category I’ve learned to associate with the highest temps.

    More analytically, and as an aside to my question, I guess a lot probably comes down to how braking heat is dealt with in carbon vs aluminum rims. There are two components to dealing with heat, generally: How fast can the rotor (rim in this case) dissipate heat, and how much energy can be put into it before it is damaged or starts braking less well. Referring again to cars and motorcycles, venting helps with the former, and a larger rotor helps with the latter. I’m under the impression that aluminum conducts heat better than CF in resin, allowing the entire rim to be a cooling surface. But drawing it back to the specific question of descending styles, hard braking over shorter distances before a corner would put a premium on a wheel’s ability to absorb the energy as heat and put up with it long enough to dissipate it over the run to the next corner, while riding the brakes would spread the heat dissipation out over most of the descent.

    Sorry for the wall of text but the assumption that riding the brakes would be harder on the rims than fast descending seemed like not insubstantial assumption, regardless of any rationale given by ride organizers.

    1. Author

      Joel, DoubleUc: I’ve yet to encounter/hear about the failure of a carbon tubular wheel. Carbon tubulars haven’t been a problem for a couple of reasons. The first is that the brake track is supported by the section of carbon that forms the tire bed, so structurally it’s a superior design. The bigger issue is that by the time you’ve heated the rim to the point that the brake track would go squishy you’d have melted most tubular glues, so the cause of any failure would be a rolled tire.

      Regarding carbon clincher braking, I can say I’ve ridden carbon clinchers that felt like the brakes were completely ineffective when wet. Zipp’s Firecrest carbon clinchers were different (I’ve ridden the 404s in wet conditions, but haven’t been caught out with the 303s so far, but I don’t anticipate a different experience); they behaved like an aluminum clincher, which is to say that braking performance suffered, but it wasn’t a complete lack of braking.

      DoubleUc, I’m not really sure what your question is regarding flat tires. If you’re asking about control in the event of a flat, I’ve not had any problems. but I do stop promptly because I don’t want to damage the rim by riding on it for any distance.

      Brian Lockhart: I know there’s a lot of interest in disc brakes for road bikes, but I’m not sold on that idea, not by a longshot. Discs bring up a whole new set of design issues; you trade one problem for four others.

      Thrash: Stick with Zipp’s Firecrest stuff and you’ll descend those roads with the same confidence and performance.

      Champs: I like the howling better than the sound of nails on chalkboard.

      Ransom: You bring up a really terrific question. Here’s what I’ve been told by the brightest minds I’ve spoken with who have been willing to be candid with me. Hard braking on twisty mountain descents produces big spikes in temperature. They can produce really high temps, but by getting back off the brakes that heat is able to be dissipated through the rim. Sustained braking won’t produce the high temps of hard braking, but without that opportunity to dissipate heat by getting off the brakes means that the temperature just builds and builds. Eventually it’s enough to overcome the curing temperature for the resin and the brake track goes plastic.

  15. Dave Kirkpatrick

    Padraig –

    Great read. I think you and the commenters make some excellent points that these are a product that has a use window that one has to be aware of. All carbon clinchers can fail. I may have seen the yeti, in that I was a first hand witness to a melted Zipp 404 FC clincher, on East Mountain Road in Killington, VT on May 31 last year – and in full disclosure it happened next to and simultaneously with a friend of mine warping one of our wheels. I think Zipp has done a good job with their engineering and stand at the head of the class on this issue, but they aren’t immune. 4 mile plus switchback descents ridden at low speeds in traffic are dangerous with rim brakes and any wheels, but carbon clinchers lower the risk threshold. Beyond the risk of rim damage, aluminum rims are a better heat sink than carbon rims – they dissipate heat much better, which means less risk of popping a tube due to heat. Just plain going down huge hills slowly on bikes is risky – witness that disc brake fluid boiling episode that was on bikerumor a few months ago. Indurain used to always use an aluminum clincher front on mountain stages because he was afraid of melting glue.

    That said, I’ve ridden my last 8000 or so road miles exclusively on carbon clinchers with no issues and little to no ride behavior modification. Use the right brake pads, keep your gear clean and well maintained, use good braking technique, and you have a broad use window with carbon clinchers. If roads with “Canyon” in their names were on my regular routes I would just plain not use carbon clinchers. For crits, normal road racing, and the preponderance of normal race training, carbon clinchers are a fantastic option. I think the one real user responsibility issue is “are you going to be able to not use these wheels for rides that are likely to take them outside of their zone?” It’s not much different than trading the ProRace4s for something more durable when you plan a ride on crappy or unpaved roads. Sometimes people don’t make that choice and oftentimes they are not made aware that this is a choice that should be made. We try hard to educate people about the appropriate use window. There is a very real marketing benefit to sweeping the limitations of carbon clinchers under the rug, and the difference between the message of “we are not confident in our rims” and “we are tremendously confident in our rims when they are used appropriately in appropriate environments” is sometimes lost in the noise.

    Ransom – Hard braking for short periods is definitely preferable to riding the brakes. Our rim manufacturer has found this in their testing and they aren’t alone in this finding. Just 4 seconds of releasing the brakes can cool the rim by 100*.


    1. Author

      Dave: Thanks for joining the conversation. It’s true that any rim will fail once enough heat has accumulated. That said, the point isn’t that you can make a carbon rim fail, it’s that with some manufacturers they are failing even when used by competent riders. If I encounter heavy traffic on a descent that causes me to ride my brakes, I’m going to pull over at some point. Sure, I’d do it with carbon clinchers because I don’t want to compromise the brake track with too much heat. But I’d also do that with tubulars because I don’t want the glue to melt. And I’d even do that with aluminum clinchers because heating up the air in the tube will cause the tire pressure to ride and traction to drop. I’ve seen a friend blow his tire off the rim by braking too hard for too long. So yes, everything can fail. It just shouldn’t fail when you’re using it in the proper manner and that’s the problem here.

  16. Pingback: RKP does carbon clinchers

  17. Dave Kirkpatrick

    “If I encounter heavy traffic on a descent that causes me to ride my brakes, I’m going to pull over at some point.” Categorically, absolutely, completely, totally. In my experience, this is not common practice. I think that events like Levi’s GF which are creating environments where people might need to employ these good practices would be well served by educating people. A lot of people just don’t know to do this – I have a lot of conversations with people who don’t know how to feather the brakes and don’t bother with their front brakes. It’s all well and good to sell these people equipment and provide venues for them to go out and have a good time, but education is key.

    Having been a witness to one incident in which two different wheels failed, my response to that was “gee, I would have approached that descent a whole lot differently” (and in fact safely rode down the very same road on carbon wheels after that stage was over). There are other instances that I’m aware of that sure seem like good practice wasn’t applied but I wasn’t there so I can’t say. I know that I haven’t seen one happen when being used with good practices but lack of evidence isn’t evidence of lack, you know?

    But heck there’s a race out here (actually in WV) called the Tour of Tucker County with a 2+ mile neutral rollout straight down a mother of a hill where it supposedly sounds like gunfire so many people pop tubes (and the promoter strongly discourages carbon clinchers and warns about popped tubes, yet still it happens). Should races have neutral rollouts like that? Should there be mandatory intermediate cooling down spots along the rollout?

    Again, good discussion, thanks for raising the issue.

  18. tiny tim

    Really, carbon clinchers? Sonoma county has some of the most neglected, pot-holed rickety, off-camber roads in northern california. Often the roads by the coast are wet (in the winter they never dry out and in the summer there is fog dew that saturates the roads). Whats wrong with aluminum rims? Sure they weigh a few hundred grams more, but the durability and braking quality and low cost put them higher on the totem pole than the carbon clinchers. In my opinion carbon clinchers are a good example of whats wrong with our disposable country-club sport that has become cycling. A two grand disposable wheelset mentality creates a sport that becomes exclusive and unobtainable. Not everyone shares this view, but those that do are the ones that buy speed, buy an image, buy youth. The very best thing thqat could happen to this sport would be a usa cycling decision that bans a bike weighing less than 17.5lb. Doing this would put everyone on the same playing field, both financially and peformance wise. One of the most inspiring things that I’ve seen is a 17 year old kid crushing the p,1,2 field on a surly pacer frame built up with 105 and 3x wheels. I think that kid took the bus to the race too.

  19. JonBoy

    This is a fantastic discussion and Padraig raises and moderates some great points of view.

    I live in LA and ride (and descend) in Malibu. For me, Dave Kirkpatrick sums it up best: “If roads with “Canyon” in their names were on my regular routes I would just plain not use carbon clinchers. For crits, normal road racing, and the preponderance of normal race training, carbon clinchers are a fantastic option”.

    On the other hand, I actually really want some carbon wheels, especially something like the Zipp 303 or Enve 3.4: super stiff, good crosswind handling, wide, lightweight, fun to ride, sexy as hell, aero etc. But for me, they’re not right. If I lived in the flatlands, I’d already be riding 404 FCs.

    It won’t be too long before we’ve moved past the era of carbon clinchers and I think we will look back and cringe. For those of us that live and ride in the mountains, carbon + discs is going to be a really nice innovation.

  20. Dave

    When I was in the army, whenever we jumped out of perfectly good airplanes, the people who packed the ‘chutes had to jump with us, using randomly chosen ‘chutes that they themselves had packed… I’d like to see some of these wheel guys use their own product on some particularly hairy descents…

    This is a problem here in N.Georgia, partly because this is the closest climbing for the Floridians…

    This descent: is the 4th descent on the annual 6 Gap century ride. Go in and look at the top speeds, high 50’s and even 60+ mph…

    Routinely, people come up and do these climbs/descents as their first experience climbing anything other than an overpass, and yes there have been problems, fatalities even…

    People just don’t know what they don’t know, and don’t find out how bad it can get until they’re deep in it…

    As you’d imagine, carbon clinchers are very popular in FLA, and a lot of those that I’ve talked with seem unaware of the dangers of using them in the mountains…

    Sadly, sometimes they don’t get a second chance…

  21. offroaded

    The melting point of aluminum is something like 1200F. The melting point
    of carbon is 6425F! We need to rename them epoxy rims -which is where the problem really lies-not in conductivity and braking patterns. Carbon carbon rims and pads would be excellent overkill here -zipp needs to stop slacking off and get on it.

  22. jorgensen

    Tossing my view of carbon clinchers aside, if I was a betting man I would be placing money on the carbon clincher rim makers to be strongly encouraging, lobbying the UCI to make disc brakes for road racing legal. As time goes on I am pretty sure it is also the number of heat cycles these rims endure that shorten their working life.

    From a rim manufacturer perspective, the chance of a consumer selecting the wrong brake pad compound is too easy.

    Bring back the 32 hole aluminum rim and traditional 3X spoke lacing for “training wheels”.
    All you guys really Need carbon rims to train on?

  23. Ransom

    As a silly aside, I now wait at a cafe (with a tasty Caldera IPA) after flatting while going *uphill* on *aluminum* rims… Big, tire-shredding nail in this case, but perhaps my first flat in a year or two is my reward for three paragraphs of red herring 🙂

  24. jasonnoco

    Excellent read. The analysis seems spot on to me.

    Question: What are your reservations about road disc brakes?

  25. Joe

    One thing I really appreciate about RKP is its scientific integrity.

    Sadly I feel that this article falls short. Exactly why is a carbon clincher so bad? How does the tire bead affect heat transfer, exactly?

    Either I’m missing something or this is some serious sensationalism.

    1. Author

      Jorgensen: You bring up an interesting point about consumers using the wrong brake pad compound—to combat that most (if not all) manufacturers include the proper pad with the wheel to steer the consumer in the right direction. However, if they don’t install it …

      And if someone wants to train on carbon clinchers, so what? Who are we to judge?

      Jasonnoco: We’re going to have to do a different post on the road disc thing. There’s so much to say, so much to be concerned about.

      Joe: My position isn’t that the carbon clincher is bad, it’s that some really can’t stand up to the rigors of a mountain descent, even when used by someone with competent descending skills. Worse, when you put a rider of marginal skills on a set, heck if you just put a rider who is timid about descending speed on them, many build up so much heat the resin softens and at that point the air pressure in the tire pushes the brake track out of shape.

      The tire bead really hasn’t been a part of the discussion; to my knowledge it doesn’t affect heat transfer in any significant way.

      Try to keep in mind this post is a response to Reynolds saying that there is nothing wrong with carbon clinchers, that people just don’t know what they’re doing. To my knowledge there isn’t another component on a bicycle that fails as readily under normal use as a carbon clincher—but only from certain manufacturers.

  26. A Stray Velo

    What I don’t understand is how can products like these reach the market if they may be potentially unsafe? Don’t bicycle wheels fall under any sort of standardized testing? I know over here in the EU all bicycles have to pass standardized EU testing or CEN/EN. Although I don’t know if this also applies to wheels.

    When it comes down to safety are there any other markets out there were it’s okay to sell potentially unsafe products?

    Scary stuff if you ask me.

    1. Author

      A Stray Velo: Every manufacturer of carbon clinchers is testing their wheels and some of them have devised particularly hellish tests to subject the wheels to. And all wheels must meet certain strength standards.

      I feel a need to back up here and remind readers that the point of my post wasn’t to position carbon clinchers as an inherently unsafe product; that’s not what I wrote. I was responding to a press release from Reynolds in which they said that rider skill was the reason why some riders had melted carbon clinchers at Levi’s Gran Fondo. My piece was a rebuttal to that.

      In my personal experience I’ve been able to descend any road I want with both Zipp and Easton carbon clinchers. And I’ve heard of zero failures with Enve’s new SES rims. There is some exceedingly good work being done out there and to dismiss the entire category as unfit for riding would be unjust. I should also add that all of the wheels mentioned work exactly as promised for most terrain.

  27. David

    I have some new Enve SES 3.4 clincher rims, and still to early to make a final judgement, they appear to be fine even on the hottest day for descents and braking.

    Nobody told me they would be smoother riding than aluminum. Very pleased.

    Still, Las Flores? Not a problem, but if I were going down Tuna Canyon in the Santa Monica Mountains, I would think twice about using carbon rims.

  28. mookies

    Primetime?…1st gen. Stratus rims? Come on…. EVERYONE melted a set of those! You can’t make a case without trying the new stuff. I have seen guys blow tires off Ksyriums on long descents too. Remember, when clinchers starting getting popular, there was a similar unease about their use in the mountains. Long descent are hard on clinchers, no matter the material.

  29. Lawrence

    I had the EXACT issue with my Reynolds Assault wheels and after 3 replacement sets going on 4 (all failing in the Santa Monica Mountains…Tuna Cyn/Las Flores). Reynolds finally told me it was rider error and they would not replace any more sets!! They gave me $500.00 cash and a set of their cheap aluminum wheels as compensation and basically told me to “F” OFF…REALLY BAD BUSINESS!!

  30. Lachlan

    I think I first read about and *wanted* a true carbon clincher in the mid-late 1990’s… Very glad I resisted the temptation when it first became a reality some years later, and despite feeling the urge at times now, I reckon I’ll be glad in another 10 years that I resisted the urge now.

    Carbon + tubs is a beautiful thing. I’ll stick with that purity when it comes to deep rims for now.

  31. Slappy

    Well on a disc front, my steel mtn bike with 8 inch rotors and xt disc brakes regularly does things like drop 4000′ on steep single track in telluride and keeps begging for more. Don’t be scared of disc, and being a broke ass bike wrench, the super base AL Reynolds I got are quite sweet and hopping on the carbon band wagon is indicative of where our cycling culture is divided with that oh so special segment heading further down the conspicuous consumption road ; 3x open proZ on lugged steel would harden ’em the f’ up! But alas yer not an American bikeraholic if money isn’t hemoraging

  32. Paul Lew


    Thanks for this article. I see that you share Reynolds’ concern for safety when it comes to carbon clincher braking. In your role as a journalist, you do right by the industry to bring focus to this issue.

    In my role as an engineer, I’m constantly raising the bar higher and trying to out-invent myself. I developed the first carbon clincher in 1998, and in the ensuing years, I’ve been focused on the importance of clincher reliability. In 2009, I developed the CTg system, which is a quantum leap in clincher reliability and durability.

    The wheels cited in your article predate CTg technology, and this concerns me because you state that you are responding to Reynolds’ press release; however, the press release is about CTg technology and the improvements it achieves in carbon clincher braking. So, it seems only right to invite you to test and evaluate the CTg system and then offer your opinion to your readers. CTg has dramatically improved brake heat resistance, and we believe Reynolds leads the market with this technology.

    We issued our press release in order to provide more information about the science behind our technology. It became clear at Press Camp that the media is ready to discuss the issue of carbon clincher safety, and while our time at Press Camp was dedicated to introducing new product, we followed up to some journalists’ questions by creating the release. We wanted to explain the steps that we take to ensure that Reynolds wheels are best-in-class in terms of safety, reliability and performance, and we were the only wheel manufacturer to do so.

    The quote you cited was my particular response to the question, “Why would an event promoter prohibit carbon clinchers?”. Since I am an engineer, and not an event promoter, I could only speculate as to why Bike Monkey would issue the statement it did. I was not speculating on the reasons that carbon rims can fail when I said that.

    It is important for me to communicate to you that my job does not end when I walk out of the office. I am not just a design engineer. I am a cycling fan in love with the sport. Cycling is my life, my passion, my lifestyle. When I design a wheel or an improvement to a wheel you can be sure that this design is intended to enhance the experience of cycling or make the sport safer.

    Cycling is what I think about most of my life. I spend an average of 25-30 hours a week riding my bicycle, on my Reynolds carbon clinchers. I enjoy competition, and I ride and race hard. I design and build equipment that is reliable, equipment that I can trust with my life.

    What I am trying to tell you is that wheel design for me is personal, and it is difficult for me to read that I am “throwing consumers under the bus.”
    > These “consumers” are my friends, family, fellow industry pals, and let’s not forget professional riders (AG2R La Mondiale) who rely on my wheels for their livelihood.

    We are all on the same team, we are cyclists, and we all want what is safe for the riders and the sport. I invite you to evaluate a set of Reynolds wheels with CTg, and I look forward to your feedback.

    Best regards,
    Paul Lew
    Director of Technology and Innovation
    Reynolds Cycling

  33. Grejsdal

    Very interesting read

    To add to the statistics. I have overheated 2 sets of Reynolds DV 46C. The first was on a descent from Kitzbühler Horn in Austria (12,5% avg. grade, 23% max, many close corners) and was after a longer process replaced by Reynolds. The second was 2 months ago descending a subsection of Monte Grappa (Monte Tomba), Italy with similar characteristics. I was surprised by the Tomba descend, and Actually stopped 2 times to cool down. But it wasn’t enough. Relative to some comments above the length of the descent isn’t a problem. I have done many big alpine passes on the same wheels. The Problem really is successive braking on very steep descents, just as described.

    I am now looking for a replacement, and its extremely hard to look through the marketing speak to real hard facts on what will actually hold up to these conditions. What would be really helpful is if someone (Velo, Tour, Peloton) would use some of these known roads to do some proper comparable tests, or maybe Zipp et al. will be smart/brave enough to take up the challenge. For me this is the primary wheel selection criteria, ahead off Aero, weight etc, and looking at the dialogue it sounds like I am not alone.

  34. [email protected]

    Always good to see discussions on any high technology product. I’ve been using and building bicycles with cutting edge components for 30+ years. As we all know, these types of products require a bit of give and take when it comes to ultimate safety.

    My personal experience with Lew’s/Reynolds products has been great. Both my wife and I have ridden their wheels for years without incident. We climb approximately 15K a week and descend plenty. That been said, pre-ride inspection of rim edge, brake track, rims, pads, pad alignment, tires and all ultra light components is a must. Not to ever throw any consumer under the bus, but quite the opposite…giving advice on safety in relation to rider ability in certain conditions has to be taken into consideration always. Once any carbon clincher flats and the carbon rim edge touches down with the road as bicycle comes to a stop, your rim will sustain some damage. Exactly how much depends on the user and conditions. Even the tiniest nick to the rim edge can ultimately affect the brake track. When combined with heat and use, this can lead to a failure as pictured. Given the age of this wheel, I would refrain from specifically blaming the product.

    Safe rides = bike maintenance, ability awareness, situational awareness and a little luck.

    Though riding and building bikes has been a lifelong passion of mine since the early 70’s, I spent 30 years as an active duty Navy SEAL and still work as the Director of Mentorship for Naval Special Warfare. In the Teams, we use a large amount of high tech and innovative equipment and understand that it all comes with some elevated reponsibility. One of the beliefs we live by is blame yourself first and the product second.

  35. JBuck

    Very interesting read. I train on aluminum clinchers and have thought about trying a carbon clincher for racing (usually each time I replace a tubular on my race wheelset). I know that I would never use a product that has such a common chance of failure during normal use. As far as Reynolds position – I’m stunned. I’ll never use a Reynolds product and it doesn’t matter what it is.

  36. Birt

    Padriag (Patrick Brady):
    I find this post rather interesting.  While I am not an expert in wheel technology I do ride a fair amount in the mountains of Colorado. I am cat 3 racer and have been riding, racing and training on Reynolds Assaults (carbon clinchers) for the past year. I’ve logged over 4000 miles on these wheels and love them. I descend fairly well and ride some the top climbs out there. My wheels are fine and brake great. I’ve ridden in wet conditions and down steep descents without any issues.  When I read the Reynolds release, it appeared that they were trying to show their braking technology and dedication to safety. Isn’t that what the entire issue is about? Your article seems more to me like sensationalism and you are capitalizing on people’s fear to gain more readership. I completely trust my carbon clinchers. If I didn’t I would not ride them. I have a wife and two kids and although I am a passionate cyclist, it is my hobby. Paul Lew simply responded to why he thought the Grand Fondo would ban carbon clinchers on that particular course and I agree with him.
    Stay safe ride hard!

  37. Chris

    All of the reviews, Velo wheel test, etc. don’t include the Campy Hyperons. Has anyone had experience with these? I have a set that have four seasons on them. They go on around Memorial Day and come off when the rains come to Nor Cal.

    Mine have been fine with Swiss-Stop pads (but screech like angry monkeys) on Bay Area descents, and I tend to follow the ‘brake hard only when necessary and let the bike roll approach’. I got some pulsing on the Death Ride last year weaving between groups, but otherwise they ride like my aluminum Neutrons.

    Just wondering if I have a time bomb here.

  38. np_lab

    So according to Mr Lew we are to believe that the “new and improved wheels” from Reynolds are the only ones that are safe for all conditions. Unless they issue a statement that limits the use of the “older” wheels, they must issue a recall and replace with the new system.

    It reminds me of the letter I sent three years ago to the Easton techs regarding their all composite forks. I wanted to know more about how they dealt with the notch sensitivity and creep in the dropouts. I heard nothing back.

    As a design engineer for an aerospace composites company, I know they need to have their operating environments defined. If those environments don’t envelope what riders may see, there should be limitations defined and communicated. By the way, when we clamp anything to our composites, we have a metallic fitting as the interface.

    For me, I ride steel and aluminum 3x wheels. The performance gains aren’t worth the increased chance of abandoning my family

  39. jorgensen

    I think my complaint about training on carbon clincher rims is that this stuff is leading (bleeding edge) technology. It is not sold and marketed that way though. It’s not the carbon that is the problem, it’s the epoxy. There are alternate chemistries, but they are not cheap. Composite structures are amazing and sometimes tender structures. As much as the fabricators have mastered, they are still many things to learn, and these are all made to a price. I really do think extended heat cycles and the number of them will show up to be an element of the achilles heel of these unless the price increases dramatically and the money goes to higher spec chemistry and processes. Carbon discs are used in Formula 1 for example and the cost of the part including the life expectancy are a minor concern. The average rider with carbon rims probably expects too much from them in the longevity dept.

    As far as disc brakes in the peloton, I give it about 3 years. And there will have to be a complete adoption. Mixing disc brakes with rim brakes will be too dramatic in the stopping distances and modulation variance.

  40. peter lin

    Thanks to Mr Lew for responding to the thread. I’ve been following the discussion and find it very informative. As a casual/enthusiast rider, carbon wheels are way beyond my budget.

    My take on the issue of limitations or weaknesses is to present the information to the user. Since I am a software engineer, we include a “known defect” list with every release. So my question is this. Shouldn’t all wheels come with clearly defined specifications that normal users can understand?

    The last time I bought new wheels was last year. It didn’t come with a manual. Do wheels come with clearly defined specifications? Of course this is ignoring the fact that most users never read the manual. End user error is always going to be an issue that will never be solved.

  41. hamncheeze

    I routinely ride on carbon clinchers, I have a pair of Edge 45s and Reynolds 66s, both circa 2009 so before the latest in rim construction from either company. I have not had any problems with them in riding and racing in my region, but most of my terrain is rolling and the longest descents are maybe 3 km. I am a very confident descender and bike handler, raced cat 1 road and elite XC MTB. Grew up riding motorcycles, raced motocross from age 8-19 and basically spent 41 of my 43 years on 2 wheels of some form, yadda, yadda.

    Last fall I traveled to Santa Rosa and did Levi’s fondo for the first time. It was a super-fun event and I really enjoyed it. Having read of carbon clincher problems in previous years, I took some well-used Campy Eurus wheels and I was pretty pleased to have done so. First, the roads in Sonoma are ROUGH. Second, when I descended the Hauser Bridge section it was kind of drizzly wet. With the wet, unfamiliar road and a few other cyclists as obstacles, I was definitely on the brakes hard and long. Part of that descent hits 22%. I found that descent to be one of the nastiest I have done on a road bike and I was darn happy to have alloy rims and my trusty KoolStop salmon pads. I am not sure I would have made it down Hauser on my Edge clinchers without a potential issue.

    I’ll be back at Levi’s again this year, but I won’t be bringing carbon wheels.

  42. Aaron

    I think one could argue that everyone is right here. Carbon clinchers AND tubulars fail from time to time. Everything fails from time to time. I’ve worked on the retail side of the industry for 15 years and now own a shop. I’ve seen aluminum clinchers fail because the brake track was simply worn thin. Carbon wheels have come a long way in the last 5 years and I feel that they are very safe and reliable. I’ve ridden carbon wheels from both Reynolds and Enve for about 6 years now and have yet to come across a problem. We have had to warranty wheels from EVERY company mentioned in the article. Some due to heat issues, some due to spokes pulling through and so on. When we discuss carbon wheels as an option, we fully disclose all the potential problems. If you are a timid descender (nothing wrong with staying alive by the way) you will likely ride your brakes more, if you do a lot of centuries where you are stuck behind riders who are slower than you, you’ll ride your brakes more. That does cause heat build up. Carbon wheels may not be the best choice. To blame the consumer is partly unfair, the retailer should be concerned with the safety of their clients and they should understand the product they sell, they should also make an effort to understand the client’s needs and it’s on them to make good recommendations. Sadly, the internet doesn’t ask you questions nor does it care about your riding style. This is why you buy from your local shop but that’s a whole other problem. Carbon wheels do perform extremely well and I have to say that for me, personally, I will always ride carbon. I do have a set of traditional hand built aluminum clinchers though for rides that may be inappropriate for carbon.

  43. ChipBeef

    My Bontrager XXXL Carbon clinchers melted pre-riding Levi’s Gran Fondo. Grew up riding and racing in NorCal and I am a good descender. Brakes failed instantly on a very steep section and then required hard braking just to modulate the speed from being out of control as the pad/rim braking surface was melted and not engaging. Both rims deformed and were ruined. Had to swap out my buddies aluminum wheel just so I had one wheel to brake with and finish the ride. Aluminum only from me for now on for big climbs and descents.

  44. Captain H

    Thank you for this very informative and honest piece on carbon wheel use/technology. Honestly, I have never understood the fascination. I completely understand the aerodynamic etc. benefit of a carbon rim for the person who genuinely benefits from their use (usually at higher speeds). However, when used for climbing (and descending), it seems as though it’s just a bridge too far.
    Your descriptions of rim failures under heavy braking loads is enough to convince me that I will probably never own (nor need) a set of carbon rims. BTW, the previous comment about seeing aluminum rims fail as well….they did so due to braking surface wear i.e. after many thousands of miles and not catastrophically. A bike shop could have measured those wheels and predicted those failures. Not so on a carbon wheel.
    I recently rode the Seattle to Portland Bike classic (back to back centuries). I was surprised to see some of the participants on carbon wheels…..doing about 17mph. As has been noted, technology is great and very important in our sport, however, every once in a while we come up with something that I think isn’t ready for prime time. Carbon clinchers is one of these.

  45. Alex TC

    I hit the asphalt at 60km/h during the first descent of the 2010 L´Etape du Tour in France. I was going down the col de Marie Blanc full-speed when my rear tire blew in a hard braking moment just before a sharp turn and BAM! I was using my ROVAL wheels, 2008 model, I believe the rims are from Reynolds (or so I was told). I finished the event, bleeding but alive, for the rims stayed perfect even after the crash and heat of the hard breaking.

    I used the Rovals the week before, and kept using it a week after in those same long, fast Pyreneean and Alpine descents without problem. The thing is, the night before the Etape I found a cut in my tire and thus replaced both. No problem there except the tour guide was prepping the group bikes so he was using the pump and filled my tires up to 130psi without telling me (or me asking him). I usually run 100 front and back in such circumstances, that´s why I never had a problem before or after.

    The wheels are perfect still, even after thousand of miles of hard use, racing and training, including some potholes and rocks and even dirt road riding. I use Zipp Carbon and Platinum pads and get decent braking even in the wet, though of course not up to an aluminum hoops.

    I confess I´m quite amazed at how much abuse those carbon rims stood. I´m light on equipment but not overly zealous, just carefull and technical. I´m not as confident riding it as I am with my HED Ardennes but then it´s aluminum and wider than the Rovals. But I can´t really say they´re fragile or something.

    I live in a place with varied terrain, we don´t have any 30km long infested with U turns but going down some roads here I reach near 100kph and some are really technical as well. I´ve been to the Andes and those are long, fast descents with technical turns and the Rovals have performed, if not up to the point of mu lovely HED Ardennes, at least decently, and they´re still alive to tell.

    I´ve seen a friend blow a DT carbon tubular during a hill climb and descent race here and it´s not pretty. To me, I trust a carbon clincher yes but whenever I need 100% confidence in my wheels, as during a hard race or in the rain, I still prefer a good lightweight alu clincher with top tires and tubes.

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  47. Tom Knox

    I am very impressed with this article. It is very difficult for journalists to report negatively on products from potential advertisers but this is an important issue. As someone who trained and raced in the Colorado mountains for over twenty years there are serious concerns about potential equipment failures especially related to the build up of heat. I learned quickly, never train on sew-ups when the route descended on sustained switchbacks beyond about 10% grade because the glue often liquified. Even the temp on aluminum clincher rims can become frighteningly hot on that type terrain. I would put carbon clinchers somewhere in between sewups and aluminum clinchers so unless in a racing situation I feel that risk is an unacceptable trade off for the performance increase. I think this was the point Paul was making. But Paul Lew expressed concerns and considering he has been a leader in composite technology for at least thirty years and has been instrumental in bringing countless innovations to cyclists I would listen to those concerns. If you live in the Mountains discs brakes future looks bright.

  48. Sam J

    I was talking with the Mavic rep in the Mid-Atlantic region a few weeks back, and he said that it has been the judgement of the Mavic engineers, after significant testing of in-house prototypes and competitors wheels, that it is not presently possible to build a carbon clincher that can withstand sustained braking forces. I know someone who had a pair of Bontrager wheels, and had them melt on a descent in the Rockies. Makes sense to me.

  49. Scott

    Disc brakes… Yes you’re right in thinking your roadies brakes are powerful, but think about the inherent safety of taking all the heat away from the rim, mountain lovers rejoice, now is the time to get seriously carbon excited – as for the weight weenies and inertia calculators, that party is about to get a whole lot more exciting as well!

  50. Steve

    I read an article that the Cervelo guys gave a presentation at Interbike and they said the same things that the Mavic guys said…Avoid carbon clinchers! Sounds like Zipp are cutting edge in the resin dept. I would stick with HED or Shimano clinchers. Go tubular if you want race wheels.

  51. Sherpa

    Padraig replied to Ransom with –
    You bring up a really terrific question. Here’s what I’ve been told by the brightest minds I’ve spoken with who have been willing to be candid with me. Hard braking on twisty mountain descents produces big spikes in temperature. They can produce really high temps, but by getting back off the brakes that heat is able to be dissipated through the rim. Sustained braking won’t produce the high temps of hard braking, but without that opportunity to dissipate heat by getting off the brakes means that the temperature just builds and builds. Eventually it’s enough to overcome the curing temperature for the resin and the brake track goes plastic.

    (Twistiness has nothing to do with heat except as a cause for braking)

    Padraig is correct that hard braking produces big spikes in temperature but the part about dissipation is questionable. When you start your 2000 foot descent you have potential energy thanks to gravity. All those Joules have to be turned into heat in your descent, with a small bit left over for your final kinetic energy at the bottom.

    Your descent heats up the air and the brakes. Someone may have the skill to descend Las Flores without touching the brakes but not me. I ride much slower than terminal velocity. What happens when I ride the brakes? The Joules are converted into heat. The rate of heating (Watts) is Joules divided by time.
    If I descend at a constant speed my rims have a N-Watt heater applied. If I halve the constant speed my rims have a 1/2 N-Watt heater in operation. The rims will be cooler. Riding the brakes is not harmful, dissipating energy quickly is harmful.

    Gravity rules. If the grade of the road doubles and the speed stays the same the heater goes from N Watts to 2N Watts.

    Pulsing the brakes will produce spikes in heating – true, but the total energy that must be dissipated will not change. The average over time will be the same (for the same average speed). However the spikes may trigger a heat failure point in the rim. Riding the brakes is not harmful, dissipating energy quickly is harmful.

  52. Scott

    I just had the chance the ride the new Roval CLX 40 & 60. Very impressed with weight, speed and the testing they did with Overend, a 50 kg backpack and Mt.Washington… AND they are relatively affordable. Mavic might be affraid of the r&d involved but I’m stoked that some companies are seriously getting it together.

  53. Neil

    Quote “The retailers I spoke to noted that what they aren’t seeing returned are Enve’s new SES rims and Zipp’s Firecrest Carbon Clinchers..”

    Quote “Reynolds had more than six times the rate of failure of brands like Lightweight”

    Quote “I know this to be true because I melted a Reynolds Stratus rear wheel descending Las Flores road”

    Are these implied comparisons really fair? I guess all manufacturers have tried to address this issue with their latest wheels, but you seem to be comparing the latest generation wheels from Zipp and Enve with older Reynolds wheels (well, not exactly, but it could easily be read that way). Any data / feedback on the failure rate of the latest Reynolds wheels with the CTg brake tracks?

    1. Author

      Neil: Try to keep in mind that the motivation for this post wasn’t some objective equipment shootout. It was a rebuttal to what I took to be blaming the consumer for wheels that consistently failed in the Santa Monica Mountains. Could I have constructed a more objective sampling? Absolutely. Were those quotes in some way unfair? Not in my view; ultimately reviewing is subjective and anecdotal. I do my best to make my work as objective as possible, but I was limited in the number of riders I could sample, and for the record, I did eliminate results from some riders who admitted they were timid descenders. As to comparing Zipp and Enve to Reynolds’ new work, no one I spoke to was riding the wheels, but I’ve spoken with Reynolds and I should be riding a set soon.

  54. steve

    I’ve read this post several times and I really like the way you’ve presented the issue. I was an early adopter (ie before all my friends) to CC’s with the Reynolds Cirrus and Stratus. I melted both pairs while riding in North Carolina. The scared shitless issue is not a small thing that can be marketed away. I then rode a pair of Easton EC90 Aero’s which I loved. They warped in Miami. Apparently they are notorious for failures and it has something to do with production at the facility in Mexico.
    To make a long story short, I’ve switched to the new Mavic Ksyrium SLR. They’re just about as light and you really can stop in the rain! Carbon clinchers give up lots of braking performance in the wet and until you squeeze an SLR you won’t believe the difference.
    I’m not a fearless descender by any means but you have to ask yourself, do you really want to worry about your wheels on a fast twisty descent? Catastrophic failure is a real possibility and Mr. Lew’s claims to the contrary, I can’t recall an alloy clincher warping.

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  57. Tim

    Hi, i found it interesting in a recent copy of Road Bike Action a report of the Gran Fondo showing both Levi and the author of the article riding S-Works Roubaix’s fitted with Zipp 202 FC clinchers. Seems to be a case of Do as I say and not as I do….

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  59. Sam

    Has the review on the Reynolds been published as I can’t seem to find any? I ask because I’m considering the Thirty Two, an older generation model.

    1. Author

      Sam: We should have some Reynolds wheels coming later this spring or early this summer.

  60. travis

    Just melted my reynolds carbon wheel on Bear Gulch… was on and off and trying to let them cool… but no luck when I turned to go up at the gate my sidewalls were flared enough to be catching the break on every revolution… Any advice on working with Reynolds?

    1. Author

      Travis: Sorry to hear your wheels didn’t stand up to the descent. That’s a bummer. Reach out to Reynolds directly and send photos. They may want you to go through your local retailer, but they may just take care of you without the extra layer.

  61. dhlywka

    I just melted a carbon fiber wheel two days ago on a steep decent. I’m 217 and was always a bit leary this may happen. this was notthe first big decent I did that day as I did one long one earlier. Coming down a longer steep decent a braked for a hair pin turn and the wheel melted and blew the tire. just glad I did not crash and get hurt. I will never ride carbon wheels in the hills again, they will only be for the flat or rolling hills.

  62. Matt

    We suffered braking damage to two pairs of relatively new carbon clinchers on a ride recently, an 2015 ENVE 4.5 and a 2012 Reynolds Attack (w/CTg brake track), both using their recommended brake pads. The damage to the ENVE was the worst of the two with the bead wall flared out, as if the brake track had softened and deformed outward from tire pressure. The Reynolds appeared to suffer delamination of the brake track. The descent was only 1.2mi and 750ft, but was twisty with some sections as steep as 15.5% (according to
    The ENVE are still under warranty and were returned to the factory for evaulation. The Attack wheels are not under warranty, but we will be contacting Reynolds about warranty replacement.

    1. Author

      Sorry to hear about your experience. Wheels have gotten so much better that failures of this sort are incredibly uncommon now. I mean, this is literally the first failure of Enve clinchers of which I’ve heard. Out of curiosity, what and where is the road in question?

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