There was a time, not so long ago, when everyone KNEW that if you wanted to go fast, you needed to run 19mm tyres, pumped as hard as they would go. This made for an uncomfortable ride, and might go some way to explaining why I kept crashing in the wet, but speed is everything, right? The only time anyone would even think of using wider tyres was for a race like Paris-Roubaix, where survival over the cobbles rated higher than speed.  Knowledge has come a long way since then, and my recent testing of Specialized’s excellent S-Works Turbo Cotton clincher tyre, in a 26mm width, has provided me with some real world experience of just what a quality wider tyre can offer.

The science
First off, let’s get some science out of the way. Recent laboratory testing has shown that wider tyres perform better when it comes to rolling resistance. In fact, the Specialized Turbo Cotton consistently rates as one of the best-rolling tyres out there, even when compared to tyres that can really be considered race-only tyres due to thin treads and limited puncture protection. 
Of course, aerodynamics is another consideration when it comes to tyres, as matching a tyre and rim carefully can result in much improved aerodynamics. Some older generation aero rims were designed with 19mm tyres in mind, and suffer a significant aerodynamic penalty when wider tyres are used. However, the latest generation of wide aero rims are designed with tyres around the 24mm to 26mm range in mind, giving excellent aero performance without the need to settle for narrow tyres with higher rolling resistance. For this test, the Turbo Cotton tyres were paired with a set of Specialized’s own Roval CLX 50 Rapide wheels (more on that in another article) with the wide profile a perfect match for the tyres.
Specialized Turbo Cotton, photo Eugene Bonthuys
The ride
One of the first things you notice about the Turbo Cotton tyres is the comfort. The generous width certainly plays a role in this, with the ample air volume helping to smooth out the often less than optimal roads I train on. The casing matches the finest top-quality racing tubulars, with a 320tpi thread count adding to the smoothness of the tyre.  The sidewalls are also finished in a classic natural tone, so in spite of all the technology packed into the tyre, the look remains understated and classic.
The tread comes courtesy of Specialized’s Gripton compound, and combined with the width of the tyre and therefore a greatly improved contact patch, it provides the most confidence inspiring cornering I have ever encountered in any tyre, even at speed in the wet, where usually my cornering confidence is a touch lacking. The tyre tread also features a smooth central section for low rolling resistance and a quiet ride, while the shoulders feature a slight file tread, adding just that little bit more confident when leaning the bike over in the corners.
Even at fairly high pressures, the tyre was supremely comfortable, and had a lively road feel that had for many years been the sole domain of high end tubular tyres. The massive air volume of the 26mm version of the tyre also allows lower tyre pressures than would be possible with a narrower tyre, adding even more comfort to the ride when required.
Specialized Turbo Cotton, photo Eugene Bonthuys
After numerous rides, in wet and dry, the Specialized Turbo Cotton has not let me down once in any aspect of testing. It has been fast, comfortable, and confidence inspiring, without suffering any cuts or punctures. I cannot think of anything else I could ask of a set of tyres – these deliver on everything. The only downside is that I have to return these and go back to my current set of 23mm tyres, and then start saving for a set of my own. I suppose that is the true measure of any product tested – would I spend my own money on it? Yes I would, and I will do so shortly.


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