How much pressure is too much? How low is too low? What’s the sweet spot? Should everyone use the same pressure? How does tire pressure affect the meaning of life?!
Big questions – we know. We receive a lot of these inquiries about tire pressure, and there seems to be no shortage of confusion and conflicting opinions. We’ll do our best to clear the air… and maybe even convince you to remove some from your tires.
For today, we’ll focus on road applications, wherein most cyclists have traditionally used a tire that’s labeled as 23mm wide. From the wheel side of things, we’ll keep the discussion focused on our 25mm-wide Plus and BLACK rims, because those are the most common products that seem to make people question our tire pressure recommendations.
The maximum pressure you should ever need to use on any Hed Plus or BLACK rim is 90 psi (6.2 bar) – even with a narrow 23mm tire. It’s true! We’re not kidding!
That’s not because 100 psi is dangerous for our rim, but because the ideal range is 65-80 psi for a 77kg (170lb) athlete. As a point of reference, the old school method said that higher pressure was always better, with many athletes using 120 psi or more for a 23mm tire.
Let’s look at a specific example to explain why this is the case. A 23mm Continental GP 4000 tire mounted on a rim with an external width of 19mm (an old-school skinny rim) has an air volume of 660ml. The same tire at the same pressure on a 25mm-wide Hed Plus rim has a volume of 958ml. In effect, the same tire is 33% larger on the Plus rim. The actual measured width of the tire grows from 23mm on the skinny rim to about 26mm on the Plus rim. So – it’s not really a 23mm tire anymore.
What are the benefits of using lower pressure? Two key things: Comfort and Speed. A larger tire puts more physical space between your rim and the road. With lower pressure, the bigger tire can compress more to absorb bumps, without having the rim bottom out and hit the pavement (which can damage the rim or pinch-flat the inner tube). The bigger the tire, the lower you can go on pressure. Of course, if you run the pressure TOO low, rim impacts can still happen.
Another way to look at this is that using lower pressure lowers the spring rate of the tire, allowing it to act as suspension for your bike. Rather than bumping, chattering, and skidding over rough pavement, your bike stays better planted. You can corner faster, and get less beat up over the long haul. You’re able to put your energy towards moving the bike forward, rather than up and down over each individual imperfection in the pavement. It can feel counter-intuitive – sometimes high pressure “feels” fast because you’re feeling every road vibration. We can assure you that it most definitely isn’t faster.
Tire pressure should be adjusted for rider weight. A heavier rider needs to run higher pressure – to avoid bottoming the rim out over bumps. A lighter weight rider can run less pressure. Our 90psi max exists because we have yet to encounter a situation where any rider would need to use more than that. Adding pressure beyond 90 would only reduce comfort and cause the rider to go slower.