Feedback from Racers: Tire Pressure Calculator 3.0
When we developed version 3.0 of our Tire Pressure Calculator, we worked with the engineering department at Cal Poly Pomona to measure how much tires deflect under different loads and tire pressures. We repeated those measurements for many different tire widths and casings, creating the largest dataset of tire behavior to date. We combined this dataset with our real-road tests of tire performance—hundreds of roll-down and power meter tests of various tires. The new tire pressure calculator doesn’t just give you a pressure that works, but the pressure at which your tires roll fastest. We built in factors of safety, too, so the output is the ‘fastest-rolling and safe’ pressure.
We also know that all the research in the world cannot replace real-world experience. That’s why we sent the beta version of our new Tire Pressure Calculator 3.0 to a select group of racers and riders. They tested how it works in the real world. Here’s their feedback:
2024 National Gravel Champion Brennan Wertz was the first to reply: “Thanks for sharing this. I really like the ‘Pro’ tab and all the different variables you can adjust.” He suggested: “I would maybe go at least a few mm above 55. Even though your tires max. at 55 mm (nominal). I often find my tires measure 1-4 mm more than the nominal width on the wide Enve rims.” Brennan is right—what matters is the actual width, not what’s written on the sidewall. We incorporated his suggestion: The calculator now goes to 58 mm.
Brennan also asked why, in the ‘Pro’ calculator, the difference between front and rear tire pressure was greater than the 1 psi he was usually adding in the back. That’s because, as a tall rider, Brennan sits further back on the bike that most of us, and thus has more weight on the rear wheel. In fact, the pressure differential would be even greater if Brennan wasn’t adopting such a low, stretched-out position—which puts him further forward on the bike than more upright bikepackers, recreational riders, or long-distance cyclist. The ‘Pro’ calculator takes all these factors into consideration, plus the need to keep the front tire inflated enough so it doesn’t collapse under hard braking—when it carries almost the entire weight of bike and rider. Brennan wrote back: “I really appreciate that!”
Jenna Rinehart wrote: “I’ve really enjoyed it, especially the ‘Pro’ calculator. It’s really made me think more about the pressure I use with Extralights versus Endurance casings. The calculator suggests pressures pretty close to what I’ve been running with the Extralight 48s, but I’ve been running the Endurance casing a little higher than recommended. I plan to put some Endurance casings back on soon and experiment with the pressure a bit more.”
Ted King commented: “The ‘Simple‘ guide is great. Keep it simple and effective. ‘Pro‘ is awesome! I’ve always wondered why pressure guides don’t ask about additional weight on your bike. Usually they simply ask rider weight and bike weight. Every racer likes to talk about how light they are, and they want to brag that their bike weighs 15.5 lbs or whatever… but they forget that added weight—water, racks, etc.—needs to be considered, too. To input this into the equation, and account for where that weight is located on your bike, is really great.”
Meaghan Hackinen tried the beta version before heading out on her record ride in this year’s Tour Divide. (The photo shows her on the way to winning last year’s Silk Road Mountain Race.) She reported: “I played around with the new calculator and felt it was easy to use. The ‘Tire Finder’ satisfied some of my curiosities—for instance: My road bike maxes out at 28 mm, but what is the ideal tire for a road bike for me? And what clearance should I look for when I finally get around to upgrading my bike…?”
Bikepacker Adrien Liechti, fresh from his Africa End-to-End world record, reported: “I like it a lot. It’s easy to use and well-presented. I like that all tire sizes are available in the same setup. Nothing to add, really.” The fact that the calculator’s recommended pressure worked well for him during his 17,280-km record ride gives us a lot of confidence!
Becca Book has been on a roll this year, winning multiple long-distance mountain bike events, plus a fair share of gravel races. Her experience with different bike types and disciplines makes her input especially valuable. She wrote: “I use the existing RH tire pressure calculator pretty regularly—happy to outsource as much pre-race stress to experts as possible! The pressures work well, except I usually go lower in wet conditions. Using the Fleecer Ridge tires on wet trails I have gone down to ~14 psi in the front. But that’s probably why you say the calculator should be used as a starting point for experimentation. So cool to have the calculator respond to weight distribution due to luggage, and have front and rear tire recommendations!”
Francesca Selva is our criterium and track racing expert (and former Italian national champion). Together with her partner, Danish pro racer Oskar Winkler, she reported back: “We both took a look at the tire pressure calculator, and it’s so cool! I wouldn’t know what to change—except you just miss the track option.” We’ll have to work with Francesca on that for version 4.0!
Natsuko also tried the new calculator. She’s on the lighter side as far as adult cyclists go, and other pressure calculators are all over the map for her weight. She tested our new calculator on her bikes with 30, 42 and 55 mm tires, and found that the recommended pressures worked well in all these cases. Which gives us confidence that the data collected in the lab by the engineers at Cal Poly Pomona really reflects what’s going on in the real world, on road and trail.
More Information:
- Rene Herse × Cal Poly Pomona Tire Pressure Calculator 3.0
- More about the racers and adventurers who are part of our R&D team
Photo credits: Jim Merithew (Photo 2); Clare Paniccia (Photo 3); Marc Arjol Rodriguez / velophoto.tx (Photo 4); Stephen Shelesky (Photo 5);
