Zipp 303 Firecrest Carbon Clinchers
My history with Zipp products goes back 14 years. In that time I’ve ridden wheelsets that scared me, cranks I thought should have been more popular than the Beatles and bars that changed my expectations for all carbon handlebars. The overriding impression I’ve had is that of a company less satisfied with its own products than intimidated by the competition.
Were I to personify Zipp’s professional ambitions, I’d say they are a lot like Eddy Merckx was in 1972, which is to say, after picking up victory after victory as if he was strolling through the Europe’s most decadent buffet with a trash can-lid-sized plate, he went on to trounce the hour record. In talking with Zipp engineers, I’ve been struck by how they really don’t seem to give a damn what anyone else is doing. They seem to begin each day with a question—how do we improve our products? And to give full credit where due, when someone else does a nice piece of work, they are happy to hand out the compliments. It’s a classy touch.
Now, you can’t begin each day with a blank drawing board; a new wheel can take a year to develop. And yet, despite their ambitions, it’s not like Zipp hasn’t had the odd black eye, such as the wheel failures the Garmin-Chipotle team suffered at Paris-Roubaix in 2008. Thought to be former winner Magnus Backstedt’s last shot at a big performance, he broke both wheels on the cobbles and ended his day in the team car. But compare that with Tom Boonen’s performance at this year’s Hell of the North, where the Belgian regained his old form and rode away from the decimated field and crossed the line on a set of Zipp Firecrest 303s.
The 303 is Zipp’s third set of wheels to use its revolutionary Firecrest shape, coming on the heels of the 404s and 808s. And while the unusual shape was roundly mocked by some of their competitors, a quick check of HED and Enve web sites shows wheels with rims with a highly rounded spoke bed, not unlike the Firecrest shape.
For those of you who haven’t been following these developments—and admittedly the nerd factor goes critical almost instantly—here’s a little primer: Wind, as you know, is the single biggest factor in determining how fast you ride a bicycle. And crosswinds affect both speed and confidence; if you’re getting buffeted by a crosswind, you’ll tend to back off and focus on holding your line. Naturally, deep-section rims are more prone to steering input by the wind. Even though the wind will push on the whole of the wheel, a wheel’s design will determine just how much force the wind can exert on it. This is expressed as an imaginary spot called the wheel’s center of pressure. A traditional box rim with 28 spokes has a center of pressure that is a bit forward of the bike’s steering axis. As you increase rim depth (think typical deep-V carbon wheels) that center of pressure gets moved farther from the steering axis, giving the wind more leverage on that wheel, increasing its ability to push you around like a mop.
Deep-V rims were design with the idea that the rim was the trailing edge behind the tire. Firecrest treats the spoke bed as a second leading edge, if you consider the portion of wheel behind the steering axis. In rounding the rim profile at the spoke bed, Zipp ended up with a significantly more aerodynamic rim. It also resulted in a rather unexpected effect—it shifted the center of pressure behind the dropout to an area very near the steering axis.
I should mention here that center of pressure isn’t a single static location, which is why I used the term “area” rather than “point.” It, like center of gravity, moves around, but instead of body position determining it, center of pressure depends on yaw angle—where the wind is coming from.
Okay, so having said all that, what it boils down to is this: Crosswinds have very little effect on the 303 wheelset. Further, when the wind hits a front 303 the effect is to steer you ever so slightly back into the wind, but practically speaking my experience is that it simply cancels out the force of the crosswind against your body and the bike.
So how much faster is Firecrest? Zipp says 8 percent faster than their previous design; that number isn’t hugely encouraging given that wheels are only about 10 to 15 percent of the overall drag of a bicycle. At best, you’re going to realize a slightly more than 1 percent gain in speed. But the gain isn’t so modest as that. Because Firecrest is that much more stable than a traditional deep-section wheel, you can ride with greater confidence and if there is a wind, you needn’t back off your effort to concentrate on controlling the bike.
Firecrest has realized yet another benefit. The wide rim—Firecrest is 25.1mm wide at the top of the brake track and 27.5mm wide at the bottom of the brake track—increases rim strength, and while that’s cool and everything, as you well know, that also gives the tire a wider footprint for better traction in corners.
I’ve ridden a lot of carbon clinchers. Some I liked, some I detested (but that’s for another post). The 303s strike an unusual balance. They are unquestionably aerodynamic. While I haven’t taken these to the wind tunnel, what I can tell you is that at crunch time on fast group rides, the 303s have aided my efforts. I notice a little something extra when accelerating or when putting my nose in the wind. The set weighs in at 1478g (676g for the front and 802 for the rear) which isn’t super light, but when combined with their aerodynamic advantage they are my favorite wheel for big jumps. And on longer climbs, when I will tend to slow down if there’s any sort of uptick in grade, a lighter set of wheels like this make it noticeably easier to get back up to my previous speed.
Unfortunately, there’s a dark side to this aerodynamic beauty. If you’re riding a Specialized Tarmac SL4 or Venge, you shouldn’t plan to mount these wheels on it. There’s very little clearance between the inside of the chainstays and the maximum width of the rim. That hasn’t stopped some riders I know from trying it anyway and claiming it isn’t a problem, but still. That whole voided-warranty thing can be a bitch.
I’ve done most of my miles on these wheels on a Super Record-equipped bike. Prior to switching them to that bike I’ll say that I had the impression that they were unusually stiff wheels, laterally. For reasons I can’t explain, the rear derailleur will rub spokes on every wheel I’ve tried when I put the chain in the big cog and stand up. I was surprised to hear the derailleur ting on the spokes of the rear 303. So it may be laterally stiffer than some, but it’s not stiffer than everything.
So that’s lateral stiffness. Vertical stiffness is another story. At 110 psi—the pressure I run most tires on most wheels—the combination of the 303s with Zipp’s Tangente clinchers is the most comfortable wheel/tire combination I’ve ridden. The difference isn’t huge; it’s not like running 80 psi with tubeless, but it’s enough to take the sting out of the rear end of a Felt F1. I probably wouldn’t have been able to note the difference had I not been riding these and other wheels on such a stiff bike.
The one consistent issue I’ve had with Zipp wheels has been build quality. On more than one occasion I’ve ridden a stellar rim and great hub laced together with a marginal build (this isn’t an issue peculiar to Zipp, though). Loosening spokes has been a recurring theme. Or at least, it was. The 303s I’ve been riding—and I’ve got more than 800 miles on them—have yet to come out of true. It’s worth noting that due to their angled brake track, if a Zipp wheel isn’t perfectly true both horizontally and vertically there can be a pronounced effect on braking. A rider will experience a high or low spot as either more or less grab at the brakes. It’s not a dynamite experience, but one I’m pleased to say didn’t take place with these wheels.
Another note on braking: Carbon clinchers and braking performance haven’t been good bedfellows. Some are as grabby as a drunk in a topless bar. Others have all the stopping power of an alcoholic at a frat party. The set of 303s I’ve been riding offer the absolute best braking I’ve experienced in carbon clinchers. Okay, so you’re wondering just what I mean by best; it’s a worthy question. What I mean is that the braking response is more similar to a set of aluminum clinchers than anything else I’ve ridden. I don’t want more stopping power, nor do I want less stopping power. I want to switch between wheels and notice only the change in sound, if even that.
And we’re not done on braking: I rode these wheels in Malibu, taking them down descents that some riders are now being advised to avoid. I’ve killed some carbon clinchers in Malibu, which is interesting given that I brake as little as survival instinct will permit. Braking is, after all, antithetical to fun. I don’t know a lot about the resins that Zipp uses, but I have at my disposal two details worth considering: 1) they have on staff an engineer with a Ph.D. in resin chemistry and 2) I am to understand that the resin used in the brake track cures at a temperature higher than any of their competitors; the brake track can handle temperatures north of 700 degrees, more than 350 degrees higher than the resins used by some of their competitors. I’ve yet to kill a Zipp wheel in Malibu; I know no one else who has done it. It’s an unusual record.
When last I dated I ran across any number of women who described themselves as “the whole package.” They were bright. Well-adjusted. Educated (graduate degree). Professional. In child-bearing years and willing. Not just healthy, but hot. They knew what they were and they weren’t going to date some guy writing a screenplay at Starbucks while on unemployment. These Zipps are kinda like that. Which is why they can ask $2700 for them.