Originally Posted by
MagnaRota
I am on 35 mm tires, rated at 75 PSI. I fill them to 85 PSI, no problems at all.
I'm confused by the posts that say lower pressures go faster. Why? I'd think that with lower pressures, the tire will be less round and thus have more rolling resistance, no?
Google is your friend. Lots of pages and videos that explain this, but basically, lower pressure reduces the rolling resistance and allows the tire casing to absorb more of the minute variations in surface as you ride. Imagine riding over rumble strips. With a very high pressure tire, your tire is going up and down each individual strip, requiring your entire bike to move up and down to move forward. Now imagine rolling over the same rumble strip on a tire with low enough pressure that the tire itself absorbs the up and down motion, so that your wheel and bike simply move smoothly forward parallel to the ground as if you were on smooth pavement.
You might also want to google "contact patch" to see the differences between high and low pressure.