The Vittoria Corsa Pro is one of the best road bike tires available and has been on the bikes of many teams throughout the season, including the Tour de France. For most of the season, the Pro has been the 28c width of choice, occasionally pushing up to 30c (especially for riders nervous about compatibility with hookless rims) and even 32c for races like Paris-Roubaix. However, at the Tour de France Grande Pearl in Florence, we spotted several riders from Team Visma - Lease a Bike using an undisclosed 29c wide Corsa Pro.

Are pro riders so sensitive to tire width that Vittoria felt the need to create a tire that spans the existing 28c and 30c?

Overall, tires are getting wider as the seasons progress. Freed from the constraints of rim brakes, both frame and wheel manufacturers are pushing the envelope, and wheels are being aero optimized to 30c widths. Visma ran a new set of reserve wheels with a wider inner width at the Classics at the beginning of the year.

The sidewall of this new prototype tire is also stated to be optimized for 25 mm inner rim width: optimizing the casing shape and tread width improves puncture resistance and cornering safety when using 24-25 mm rims, while maximizes the aerodynamic benefits of these rims"

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While the claimed aero benefits are not surprising, the reference to "cornering safety" is what piques the curiosity of the Cycling News technical team the most.

Two major selling points of the wider inside rim are that the lack of a curved lateral cross-section allows for a wider contact patch, which improves stability in corners, and a more stable tire sidewall during hard cornering. Since the sidewall is directly over the rim wall, it prevents the rim from bending. However, the wider rim width, coupled with the fact that 28c continues to be used as the nominal standard width for professional use, has had unintended consequences.

For the same tread width, widening the bottom of the tire also reduces the lean angle required to initiate cornering at the sidewall of the tire. The only way around this is to use a wider tire, but then the benefit of supporting the sidewall is lost and the weight increases.

I suspect that the 29c width was developed by Vittoria at the request of Vimalise-a-Bike, at least in part, to allow riders to corner harder. We have communicated this hypothesis to Vittoria, but have yet to hear back from them.

There is already evidence of this happening with very similar setups. Alec Briggs of Team Tekkers in the UK is running reserve wheels and Corsa Pro tires, and a recent Instagram post clearly shows how far off the tread he is on the tires. I think the rims are too wide for the tires." to which he responded with a clear answer, "Yeah, basically."

Extending this thought to UAE Team Emirates, Tadei Pogachar was on 30c tires early in the Tour. However, it is not certain whether he used 30c on every stage. The Enve rims used by the team are also wider than usual, and cornering ability may be the reason here as well, rather than simple aero optimization.

Judging by how hard the Slovenians were riding on the descent of the Col du Galibier on stage 4, that was surely on the racers' minds during the reconnaissance ride.