Originally Posted by
tetonrider
i run less. for me, i've never found a situation where lower press is slower on the road (if you're racing track, different story), and tubulars have reduced risk of pinching. pinching is the reason i won't run clinchers lower.
consider terrain that pushes the tire. an extreme example is MTB (yes, i do have tubulars for MTB), but cross also illustrates the point. you can run 20 or more psi lower with tubulars. for road, the difference is less dramatic due to smoother terrain overall, but at a micro level the same stuff is happening.
for the same pressure and otherwise apples-to-apples (handmade tubular with cotton casing + latex tube vs open tubular of similar construction and latex tube), the tubular will be a bit more supple than the clincher. you can run a higher pressure on the tubular and maintain a similar fee.
I'm not sure I agree 100%; there is a point where lower pressure will be slower due to deformation. The crazy-low pressures we run in 'cross tubulars (example: I am 125 lbs and depending on the course will run as low as ~20f/22r in 32mm tires, plenty go even lower than that) are faster because they keep the tire in better contact with the ground, and because surface irregularities means the tire is doing a lot more work and softer makes for less work to deform it. It's just a completely different environment for the tire than you have on the road, where most of the deflection in a tire is from the weight on it, or from cornering forces. On the road, folding more rubber than you need to in order to keep the tire on the road is just wasting energy.
The other issue with lower pressure is the effect of cornering forces on tire shape. Lower pressure means the tire can't resist lateral forces as effectively, so it could fold a bit. In theory, this hurts cornering precision. In practice, I'm not sure how much of an issue it really is on the road. It's a real thing in cyclocross, where those sub-30 PSI pressures make tire folding a fact of life. But in cyclocross we deal with it because we basically have no choice, not because flopping around on soft tires feels great.
Overall, I agree that most people ride on much higher pressures than necessary. Over the years I've come down to something 80f/85 r for racing on 23mm clinchers and have not found that it slows me down at all. Even keeping in mind that I am light, I'm running tires at well below the pressures they are designed for, and could probably get another 5-10 PSI out of them before they started feeling too squishy. But then pinch flats become a risky. Eh. Tire pressure is an arcane subject. But I think the conventional wisdom of running road tubulars at slightly higher pressures than clinchers is basically sound.