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The idea that super-skinny, high-pressure tires are the only way to go for athletes who hope to hit blistering speeds on the tarmac was a pretty consistent line of thought for a long, long time. It makes sense, right? Less surface area means less wind and rolling resistance, not to mention weight savings. Those three categories are usually at the top of every triathlete’s list when selecting a tire for race day.
More recently, however, research has shown time and time again that wider tires running at lower pressures may actually be faster and (definitely) more comfortable than max-PSI skinnies to which many riders have become stubbornly accustomed.
Most tri bikes are right at home with tires ranging from 21 to 25mm wide—and many agree that 25mm is already a vast improvement over the 21mm and 23mm standard that triathletes have long adopted. But a growing cadre of both riders and manufacturers are beginning to move toward a 28mm standard.
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For example, ZIPP’s new 858 NSW features a minimum tire width of 25mm, while the brand sets the optimum tire width for all riders at 28mm. Furthermore, the maximum recommended tire pressure for the 858 NSW wheelset is just 73 psi. All the rest of ZIPP’s hookless, tubeless compatible tires are about the same.
SRAM’s online tire pressure guide paints an even more drastic picture. For example, SRAM recommends 56.9 to 60.6 psi for a rider weighing in at 165 pounds on a 20-pound bike with 28mm tires mounted to a 23mm-wide rim—this is in stark contrast to the 100 psi (or even 90 psi) rule of thumb that most triathletes probably use while training or racing.
“In triathlon, running wider tubeless tires at lower pressure makes you faster while also smoothing out the ride so your body is fresher for the run,” according to ZIPP.
ENVE also has gotten into the 28mm scene with the ENVE 65 and 45 which are optimized for tires ranging from 25mm to 28mm. Likewise, ENVE’s SES 6.7 is optimized for 27mm to 28mm tires.
“The SES 6.7 has been aerodynamically optimized around a labeled 27mm tire, since data shows unequivocally that in real-world riding conditions a higher volume tire provides more speed, confidence, and control,” ENVE said. “Featuring a 23mm internal rim width, the SES 6.7 can be paired with a 25mm tire, but for those wanting to decrease rolling resistance and maximize speed, a 27mm-28mm tire is the optimal labeled tire width.”
ENVE recommends a tire pressure of about 90 psi for the SES 6.7.
There’s no shortage of wheelsets for riders who fancy a thicker tire option. But do 28mm tires really stand to sweep the triathlon scene? And, do they really offer improvements over their skinny counterparts?
Zipp says wider tires make riders faster primarily by reducing energy loss from the vibrations that would transfer through a bike and rider with skinnier, firmer tires.
Wider tires and rims also contribute to wider and shorter contact patches with the ground that makes it easier for the wheel to roll, especially over imperfect terrain, helping to decrease rolling resistance ZIPP said.
Harold Wilson, a longtime coach and owner of Brains and Brawn Coaching based in Austin, Texas, tends to agree with that assessment.
“I definitely think it’s a trend that’s taken off,” Wilson said, adding that the deep-section carbon wheels he uses for triathlons seem to also be getting wider and wider.
“I think most of the wheels are spec-ing that they work best with 28mm tires for aerodynamic profile,” he said.
So should you run out and buy 28mm tires? Not exactly. While wheel manufacturers are pushing 28mm tires, there are some real-world considerations that triathletes have to address before making the switch: First, if you have rim brakes, there’s a chance you’ll be stuck at 25mm or less, as few rim-brake wheels are optimized (or even fit) 28mm tires, so check your wheel specs first.
Furthermore, even if you do have disc brakes and a wheel that can accept 28mm tires, there’s the issue of frame and/or fork clearance, as tri bikes leave notoriously little room for extra air. Make sure those fat tires will fit within your frame and fork without being so tight that they could rub—causing a potentially dangerous situation.
Wilson, who has been competing in tri since the 90s, said he usually isn’t one to immediately jump on a new trend and abandon the traditions associated with cycling, but 28mm tires are one that he has adopted.
But the move to wider tires is not a brand-new development. Wilson said he heard murmurings of the move toward wider tires from another rider during a group ride before the COVID-19 pandemic began.
“He was talking to me about the technology of the 28mm tire that is going to be coming out and the science behind it. But when I first talked to him about it, I was like, ‘Yeah, no. I don’t know about that,’” he said. “Now I see that I was completely wrong about that. That’s definitely the way the industry is going.”
For Wilson, who purchased a new bike spec’d with 28mm tires earlier this year, he said running the wider tires has paid dividends. For one thing, some wider tires do not produce as distinct of a bulge at the point where the tire and wheel come together, improving aerodynamics.
But the biggest payoff is comfort—something that’s actually very important for triathletes who have to run off the bike during races. He said using even lower pressure during training rides makes long training efforts easier on the body, and he is less likely to get a puncture, which can be real energy drains in themselves.
Wilson said that when you spend as much time in the saddle as triathletes every week, any boost in comfort helps.
“Maybe over a two-hour or three-hour ride, you may not notice it as much,” he said. “But when you start getting up to that four-, five-, six-hour ride range, you start to notice.”