In a message dated 3/21/02 10:04:46 PM Eastern Standard Time, CaptBike@sheldonbrown.com writes:
<< Ed Kasper mused:
>I guess it wouldn't have anything to do with the greater weight distribution >over the rear wheel and resulting larger contact patch, or would it? >
<< Sheldon Brown amused:
The rear tire shouldn't have a larger contact patch if properly inflated, unless a wider tire is used in back.
Any difference would be a function of the width of the patch, not its area, so even if tire pressure were equal front/rear (not good policy) the difference in patch width is teeny. >>
Sheldon, Actually, I was a little bemused that you didn't agree with the reasoning that greater weight over the rear wheel contributed to the higher incidence of rear punctures. I only inflate my rear tire 5-10psi more than my front, so my fat arse makes the rear tire squirm like a pig in mud, but for the sake of our thought experiment, lets say I pump up the rear enough to make the contact patches roughly equal. Am I not correct that at this higher rear tire pressure and inversely smaller contact patch area, greater force per square inch is exerted on the rear, thus increasing susceptibility of puncture versus the front wheel? Otherwise, my whole puncture paradigm perishes! I like the generally accepted "dancing shard" postulate you espouse, especially at low speeds, but at greater speeds I have noticed the front tire seems to 'fling' debris in a random pattern, usually away from the rear tire. So I propose further study and perhaps a new Unified Puncture Theory will be formulated. Maybe we can enlist the support of the Tri guys and gals, with their more even wheel weighting, to give us some empirical support. But some of those swimmers and runners probably underinflate, and will taint the data with pinch flats. <wink>
-Ed "Only rides a fatter front tire in the dirt" Kasper (otherwise how could I justify those carbon forks)? Detroit MI
"People are usually more firmly convinced that their opinions are precious than that they are true." -George Santayana