Fact: Narrower tires (such as 23 mm) have less rolling resistance than wider tires (such as 25 mm) when each are pumped up to their recommended pressures, such as 110-120 psi for 23 mm and 90-100 psi or less for 25 mm. 28 mm are far slower when used at their recommended 80-90 psi pressures.

The myth that wider tires have less rolling resistance for triathlons ONLY holds true if you pump your wider tires to the exact same pressure as the narrower, higher pressure tire.

Reducing rolling resistance is a direct function of having higher tire pressure minimizing hystersis, not tire width. Think about it, why are train wheels made narrow and out of hard steel instead of wide, thick rubber that flex even though both can support the same weight?

So why wouldn't you want to run 28 mm width tires on your tri bike pumped up to 110 psi so that you can minimize the rolling resistance over 23 mm tires? It's because the volume of air in the tire grows in a power of 3 relationship to the tire width and it is the pressure x volume of air that produces the net stress at the clincher bead of the tire threatening to blow the tire off. So you will always have more rolling resistance in a 28 mm tire because you cannot pump it to as high of a pressure as narrow tires because the force exerted at the rims will be unsafe.

Don't listen to all the marketing saying wider tires are faster for triathlons, it is a complete myth that hinges on you pumping up your wider tires to above safe limits.


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