Obviously, if your tire is flat, rolling resistance is very high. So there is a minimum pressure below which rolling resistance increases. In our testing, we found that this pressure was about at the point where the tire no longer cornered safely - pretty low!
There also must be a maximum pressure beyond which tires become slower. At infinite pressure, the tire would be totally stiff, and then you'd be back to the old days when wheels were shod with narrow strips of rubber. Those were very slow. In reality, the pressures we tend to ride are in the middle - even 200 psi isn't making a tire totally stiff - so we don't need to worry about it. Basically, a Grand Bois 700C x 32 mm (or Vittoria CX Corsa 25 mm) tire is as fast at 60 psi as it is at 200 psi. At moderately high pressures (110 psi or so), they actually were a little slower, but this is a minor effect. While statistically significant (so it's not noise in the data), running your tires at 110 psi will only make you marginally slower than running them at 60 or 80 psi. I am quoting from memory, the exact data is in the *Bicycle Quarterly* article (Vol. 11, No. 3). So for practical purposes, tire pressure should be selected as low as you can go while still getting good cornering. This holds true at least for high-performance tires. We haven't tested this for sturdy, belted utility tires, but if you are concerned about performance, you won't run those, anyhow. Jan Heine Editor Bicycle Quarterly http://www.bikequarterly.com Follow our blog at http://janheine.wordpress.com/ -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/groups/opt_out.
