Originally Posted by
Russ Roth
You realize that based on the chart you posted, your comments here are total BS? The only time they run the tires below 60psi is on the drum, the rest of the data points start at 60psi and your estimate for lower pressures is an extrapolation of what you think the result would be based on the curve. The reason they probably didn't go lower for any other surface is something well understood by those of us who started racing on narrow tires; pinch flats suck and walking is slower. Again, my reply to you was that when it came to 20 and 23c tires, dropping down to low pressures would result in pinch flats, this is real world experience. Your "proof" is specifically for 25c tires, even the testers don't go below 60psi, and the optimal pressure for a 25c tire over the surfaces I generally ride is a solid 100psi, not some ridiculously low pressure. Not that I think smd4 has the right idea with his 140psi, personally I think that's nuts, but arguing an equal extreme in the other direction won't get you any further and ignoring the tire size he says he pumps up to that ignores the way these data points change with tire width.
You missed the point entirely. The point was to emphasize that it is as bad to use 140psi as it is to use 60psi. Both are slow. It is best to use a tire pressure near the break point, which in the case of the test behind said graph was around 110 psi +-10psi.
Granted, 140psi is unlikely to result in pinch flats, but it is more likely to result in loss of traction when cornering, loss of control on rough sections, increased punctures due to penetrations etc.
As I mentioned earlier in my reply to cycco, the need to vary pressures with a particular tire, width, rider weight etc. is such an obvious self explanatory thing, that I didn't really see the need to emphasize it separately. I see now that I may have been wrong. Perhaps in the future I'll need to mention in every post that gravity is a thing and that is causing all kinds of effects you need to prepare for. And to remind people that they need to breathe during rides. And not to ride bikes underwater. You see where I'm going with this?