Specialized Tarmac SL3, Part II

Before I jump too far into the second half of this review, I need to mention that the bike as shown here was shot after I’d put a good 2000 miles on it. Normally, I shoot bikes as soon as I get them, but somehow, my excitement to get on this machine saw me flame out on that mission. As a result, you’re seeing it with some non-standard parts, including a replaced rear tire, a compact crankset and a compact bar. I swapped the cranks and bar out for my personal preferences. Had I been purchasing the bike off the showroom floor, I’d have put those parts on eBay before ever riding a single kilometer. Okay, on with the real subject.

I had an interesting conversation this past fall with one of Specialized’s engineers. We were discussing how stiffness isn’t an absolute, how a bike needs to flex in certain directions to track well, as well as provide some comfort to the rider.

What he told me was that stiffness, as a concept, required a lot of flexibility, that when they use the word “stiffness” they say it with a wink. To understand this, let’s begin with a simple example: a fork.

A fork, generally speaking, can flex in a few different ways. The blades can flex fore and aft. They can flex side-to-side. They can twist. And the steerer can flex based on twisting forces exerted by the rider. Of these, one—fore/aft—is useful. The other three are not helpful in making a bike track well when under power, cornering or descending. So the trick is to vary the sheets of fiber so that you’re minimizing twist, sideways and steerer flex while allowing the blades to respond to bumps and vibration.

When you get to a frame, how and where you want stiffness and how and where you want flex gets a good deal more complicated. In the late 1990s, the challenge was to eliminate bottom bracket flex. Once that was conquered we started noticing how frames would twist when we were out of the saddle.

One way a manufacturer can address stiffness while keeping an eye on weight is through the addition of ribs. There are a number of companies using ribbed construction these days, though it’s still a technology in the minority. To picture it, imagine looking at a round frame tube from one end. Now, imagine a wall of carbon fiber running vertically from the 12 o’clock position to the 6 o’clock position. That’s how it’s used in the down tube. Other tubes orient the rib 90 degrees from that. Pretty straightforward, but it can be difficult to picture if no one bothers to explain it.

I’ve seen enough snarky comments about “torsionally stiff and vertically compliant” to know that most readers are at best highly suspicious of this claim and at worst think its as achievable as domesticating a unicorn. I’ve had the chance to ride enough different bikes at this point that I know some are more comfortable than others. There’s no mistaking a frame with a small amount of vertical flex. Similarly, there’s no mistaking a frame that doesn’t have enough of it. What a few different engineers have told me is that if you vary the orientation of sheets of unidirectional carbon fiber so that some are at 45 degrees to the primary orientation, that will soften the feel of the frame some. It can make a big difference in how harsh the chainstays are, I’m told.

Here’s the thing about the Tarmac SL3: I didn’t really like the SL2. I loved the SL and thought it was a terrifically stiff and precise bike. The SL2 squared the function and to me it was overkill. Specifically, I thought the rear end was harsh. Riding one on a rough road left me with the concern that maybe I should have worn a kidney belt like the motorcyclists who ride hardtails do.

On the SL3, the seatstays were slimmed up and flattened in a manner similar to the Cervelo R3, though not to the same degree. That and other changes to the rear end took the edge of the bike’s harsh feel at the saddle. Meanwhile, the front end remained crisp feeling. The original SL seems like a pig by comparison. The frame has also lost somewhere in the neighborhood of 100 grams. I haven’t weighed the stripped down frame, but I’ve seen several sources report that a 56cm frame weighs around 850g. There are a lot of claims about sub-900g frames. Very few are true. That the SL3 has been independently confirmed to weigh around 850 should impress you.

Part of the Tarmac’s crisp feel comes from the fact that it doesn’t suffer the weight of several glossy coats of paint. Paint, as I’ve mentioned previously, can add 100 to 120 grams of non-structural weight to a bike. All it does is deaden the feel of the bike. On a descent I want maximum feedback, which is why I’ve found I prefer matte-finish bikes.

This bike was equipped with a number of Specialized products. The traditional-bend bar I removed was light, the lightest handlebar I’ve encountered other than the Zipp. It seemed plenty stiff, but I just couldn’t force my hands into those bends, no matter how many Euro PROs run them. The Roval SL45 Rapides are wheels I didn’t expect to like. While they weren’t super-easy to wind up (that has more to do with my lack of a sprint than any inherent problem with the wheels) they were more stable in wind than I expected, though not Firecrest stable. The combination of carbon fiber aerodynamics and an aluminum brake track offers day-to-day reliability and performance that are hard to argue with.

I’ve heard the carbon crank criticized for flex. I’m not sure why. It was terrifically stiff for me and because I’ve ridden carbon cranks that flexed—a lot—I can say these were quite different. The best feature about the cranks is how once a lockring is removed you can simply pull the spider and chainrings off and replace them with something different. So while mine came with 53/39 rings, in a matter of minutes, one of Specialized’s most experienced techs had a compact setup installed. That change saved my beans later that week when we climbed above 9000 feet.

I’ve ridden a lot of great bikes. Many bikes I really didn’t want to send back. I’m in love with this thing. It’s easily in my top three favorites of all time, though that may change next week when I get on the Tarmac SL4. I’ve done a few miles on one already and I can say there is definitely a difference, but that difference is really only apparent if you’ve ridden both bikes within a day or two of each other. Had they not come out with the SL4 there would be no reason to think that Specialized was off the back in some way. Indeed, before I got on the SL4, I couldn’t help wondering if they weren’t solving a model-year problem as opposed an actual performance issue.

Here’s the thing to think about: There are Specialized dealers all over doing what they can to get this model out their door. And the new Pro-level bike is the SL3, so while my review bike retailed for $8100, the new Tarmac SL3 Expert Mid-Compact gives you this frame and fork for only $3900.

Like I said, one of my favorite bikes of all time. It’ll be a long time before I find this level of performance inadequate.