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Rolling resistance has become one of the hottest topics in road bike performance in recent years, and tire companies have been quick to capitalize on the potential gains with a flurry of open tubulars and otherwise-traditional vulcanized clinchers that are built with more flexible casing constructions. And the growing popularity of retro-looking tan-wall tires has only accelerated the return of cotton and other more flexible casing materials and constructions.
Speed is one thing, though; durability is another entirely, and Enve Composites is now saying that there seem to be some big problems with the latter.
Specifically, Enve says that catastrophic tire bead failures — on the sidewalls, right at the bead hooks — have been occurring more frequently than in years past. In addition, and more importantly, Enve contends that this is happening with other brand’s wheels as well, and is a problem directly related to the tires themselves.
Pushing the envelope a little too far?
According to Enve, these failures are due to certain types of high-performance road tires being built with extremely lightweight and supple casing materials, but without any additional reinforcement to protect them where they interface with the rim.
“Rolling resistance is the new religion in the bike industry, and it’s getting pushed to the outer limits,” said Enve chief engineer Kevin Nelson. “You want to generate flex to absorb road vibrations, but in doing that, you’re going to fatigue a material. It doesn’t seem to be specific to carbon, or even if it’s totally clear that the [tire] materials are the only factor, either.
“You’ve got a perfect storm of things here,” Nelson continued. “You have softer and lower tensile-strength casing materials being used to generate flex, and then the more flex you have, the more fatigue you’re putting on those fibers, and then you’ve got lower pressures, which are also generating more of that localized movement, and then bigger tires. All of those things are combining for sure.”
To be clear, Enve isn’t yet certain if the issue is related specifically to tire casing fatigue (from repeated casing flex) or abrasion (from the casing repeatedly rubbing on the edge of the rim), or some combination of both. And the issue is related more to what the tires are made of, and the method of construction, than the color of the sidewalls. But nevertheless, certain tires have consistently failed in as few as a few hundred kilometers in the company’s in-house testing.
According to Enve design engineer Clint Child, the tires’ susceptibility to damage doesn’t seem to directly correlate to rim material or rim geometry. And what’s perhaps most worrying is Enve’s claim that many tire companies don’t seem to be addressing it as seriously as they should be.
“We called up the tire companies, and they were fairly dismissive about it, frankly,” Child said. “They tell us, ‘Oh, that’s a race-day-only tire that isn’t meant to go that many miles.’ But the problem is that nobody knows that; that’s not what their web sites say. So customers are buying the tires, shops are recommending them, and people are getting hurt. [The tire companies] are not owning it. That’s why this seems like a fairly aggressive approach, but I think we all collectively feel something has to be done to call this out. At a minimum, people need to know the risks they’re taking by running these tires on a day-in, day-out basis.”
Enve has released a preliminary list of tires that are either explicitly approved or not approved for its carbon clincher rims, but Nelson and Child are careful to point out that the list is hardly exhaustive — and officially, it’s so far only been communicated to Enve dealers and registered wheel owners (CyclingTips obtained a copy of the email from a dealer).
Although “over a hundred” different tire models have been tested so far, there are still lots more to test, so that list will surely evolve moving forward. A few notable omissions include Specialized’s Turbo Cotton tire, and anything from popular brands Donnelly, Veloflex, or Compass/Rene Herse.
Nevertheless, Enve’s current list is as follows, and we’ll continue to dig into this story as it develops.
Challenge handmade clinchers (all models)
Vittoria Corsa non-tubeless
Specialized (with the exception of the 28mm-wide S-Works 2Bliss model on the SES AR 4.5 Disc rim)
Vittoria (with the exception of the Corsa model mentioned above)