Originally Posted by
Kapusta
Yes, there is a lower limit... and the larger the tire, the lower that limit is. Thus, as a I said, the larger tire alows lower pressure.
As far as rolling resistance.... Sure, if you drop it too much you will have more resistance. But if - as you say - the larger tire rolls faster at the same pressures, then you can drop the pressure until the RR is the same.
Why try to match the rolling resistance to the narrower tire? If that is the point, why not just run the narrower tires? They are lighter.
Out of curiosity, do you run the same pressure in a set of 25s and a set of 38s?
Very close. I’ve looked at calculators and they give me ridiculously low pressures. Calculators have given me a pressure for a 28mm tire of 78psi for the front and 114 psi on the back. For a 37mm tire, the pressure is 46psi and 69psi, respectively. I would never ride at either of those pressure for the 38mm on just about any tire. First, I hate riding on flat tires. I’ve ridden tires at that kind of pressure when the tire is going flat and I don’t simply don’t like it. At those kinds of pressures, I’d be bottoming out the tires on even small bumps. Alternatively, I wouldn’t run 114psi on the 28mm tire. I wouldn’t run that pressure on a 23mm tire. I use about 100 psi for both.
I don’t ride 37mm tires much. I might go as wide as a 35mm tire on a road bike but seldom wider. The calculator suggests that I use 60/92 psi (front/rear) for a 32mm tire. 90 psi is about what I use for that wide a tire.