A wide gravel tire is likely to give you a tire pressure recommendation on a rough surface that would put you at risk of pinch plats with a standard clincher tire. The math is the same for tubular, clincher, and tubeless set ups, but only a tubular tire is going to be capable of handling that tire pressure without ruining the rim. A good place to start for a high quality 20mm tire on a wooden velodrome is 187psi. You might also have something at one of the extreme ends like a wooden velodrome. The tire casing for example does make a difference in the calculation so a high-quality tire will move the breakpoint tire pressure higher because the casing is more efficient. Just because the breakpoint tire pressure calculation is the same between a tubular, clincher, or tubeless set up doesn’t mean all three don’t have their place. On this topic, when tire manufacturers print a tire pressure on the sidewall of the tire, it doesn't mean you can't go lower than that. Don't run 80psi on rims only rated for 60psi. This is important to keep in mind when comparing calculators and to follow any limitations especially on the high side of tire pressure ratings. This is most likely why some other tire pressure calculators out there will have a different rating than we do. We don't make wheels or tires so we aren't limited by our own products in the recommendations we provide. The better the tire the less steep that curve is which means you aren’t going to lose as much by running a few psi too low or too high, but the same idea is the same from 4” Fat Bike tires all the way down to your 19mm onion skin track tubulars. How high can we inflate the tires before surface impedance takes over and begins to raise the rolling resistance again? Across every test we have seen tires get faster as you increase the pressure right up until they don’t. Simply put, we are calculating the break point tire pressure in our Tire Pressure Calculator. The rougher the surface, the smaller the tire, the lower that breakpoint pressure is going to be. The losses in the system shoot back up because it is now the surface impedance that takes over. Below you can see his test that follows the same curve as the roller test closely on this “good” pavement surface right up until it doesn’t. This breakpoint is where casing losses are no longer the leading contributor, but surface impedance becomes the driving force to slow you down. When the surface is extremely smooth like on a roller or a wooden velodrome casing losses account for the vast majority of rolling resistance which is why you would want to run pressures exceeding 140psi. When real world testing started to be done by Tom Anhalt, he found that there was a breakpoint pressure. This is because all of the testing at that point had been done on roller drums which are extremely smooth surfaces. We thought that to be true and even “tested” it to be true. We have long been told that higher pressures are faster on the road.
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