Don't get it...
Discussion
Got a Trek 7.5 for commuting. I've had it just over 2 years and have put about 5-6K kms on it commuting to work in that time. It still had the Bontrager Hardcase lites on which I used to run at ~ 100PSI. (700 x 32C)
The front tyre developed 'acne' this morning - nice bulge in the top so cycled slowly into work and went to my LBS to get some new tyres.
All they had hardcase wise was the Bontrager all weather jobbies and given that I had to get home in the evening, I took those.
The new tyres have a Max PSI rating of 50-85. Erk...So I stuck 85 in and cycled home. To my surprise, I went faster than on the hardcase lites ? How ? I thought (probably mistakenly) that a higher PSI reduces rolling resistance and therefore = more speed
But tonight proved not to be the case...I'm a bit confused by this now !
The front tyre developed 'acne' this morning - nice bulge in the top so cycled slowly into work and went to my LBS to get some new tyres.
All they had hardcase wise was the Bontrager all weather jobbies and given that I had to get home in the evening, I took those.
The new tyres have a Max PSI rating of 50-85. Erk...So I stuck 85 in and cycled home. To my surprise, I went faster than on the hardcase lites ? How ? I thought (probably mistakenly) that a higher PSI reduces rolling resistance and therefore = more speed
But tonight proved not to be the case...I'm a bit confused by this now !
How ? I thought (probably mistakenly) that a higher PSI reduces rolling resistance and therefore = more speed...
Generally, lower PSI means the tyre can deform over and swallow up bumps, rough road surfaces etc, etc. A "harder" tyre at a higher PSI can't deform. Instead is has to hit, roll up, over and down the other side of any obstructions (the aforementioned bumps, rough road surfaces and whatnot). This saps energy and slows you down. There is a trade-off in increased risk of pinch-flatting, and of going too low WRT pressure and riding around on something resembling a flat, with corresponding drag...
Generally, lower PSI means the tyre can deform over and swallow up bumps, rough road surfaces etc, etc. A "harder" tyre at a higher PSI can't deform. Instead is has to hit, roll up, over and down the other side of any obstructions (the aforementioned bumps, rough road surfaces and whatnot). This saps energy and slows you down. There is a trade-off in increased risk of pinch-flatting, and of going too low WRT pressure and riding around on something resembling a flat, with corresponding drag...
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