Lower rolling resistance is clearly an advantage that matters to racers, and there seems to be consensus across the industry that the best tubeless tyres really do roll faster than the best tubulars (and the best conventional clinchers).
Specialized, for example, claims its newly launched Turbo RapidAir tubeless race tyre saves 2.8w at 40km/h against its tubular counterpart (in lab conditions with a 45kg load, at 7 bar / 101.5psi) while Schwalbe’s new Pro One is claimed to best the Pro One HT tubular by an astonishing 17 watts at the same pressure and the slightly higher speed of 45km/h. (The load wasn’t specified.)
And if you head to Bicycle Rolling Resistance and do some side-by-side comparisons, the tubeless options invariably win out.
What constitutes an apples-to-apples comparison is a little murky, however; particularly when pitting technologies as fundamentally different to one another as tubulars and tubeless.
The construction of the tyres is completely different and indeed tubulars and tubeless tyres of the same nominal width, from the same manufacturer, may measure up quite differently when mounted.
There are other variables too. Jan Heine of René Herse Cycles/Bicycle Quarterly — himself a long time proponent of super-supple wide tyres — isn’t anti-tubeless, but he is convinced that the use of sealant in tubeless tyres largely negates the supposed reduction in rolling resistance they offer.
Bicycle Rolling Resistance’s Jarno Bierman doesn’t agree. In a report published in 2014, he found that 30ml of sealant in a 25mm road tyre increased rolling resistance by just one watt at 36km/h — a penalty far smaller than the typical advantage tubeless tyres hold over their clincher and tubular counterparts.
For what it’s worth, when BikeRadar ran its own performance tyre lab tests with help from Wheel Energy back in 2017, the original tubeless Schwalbe Pro One trounced all of its standard clincher competitors with 25ml of sealant on board.
There is one huge caveat to all of this: we’re still talking about a tiny difference in performance here. Rolling resistance matters, but at bike race speeds it’s a small part of the overall picture, with the vast majority of a rider’s energy expended fighting wind resistance.
On that front, SRAM’s Geoff Przekop raises an interesting and perhaps rather overlooked point: “We have consistently measured that clinchers [including tubeless] are more aerodynamic than tubulars, starting way back with our Firecrest development more than 10 years ago.
“Of course, the specific results will vary depending on the individual rim and tyre designs, but we see very few exceptions to this trend when testing. Specifically, clincher tyres tend to outshine tubular tyres as yaw angle increases above 10 degrees — potentially due to the cleaner transition they exhibit between tyre and rim outer diameter.”
Ultimately, a pro’s job is to win races though, so if there’s a real performance gain — however marginal — they’d be a fool not to embrace tubeless, wouldn’t they? How about you?