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Tire Strength Question(4 posts)

Tire Strength QuestionPEDDLEFOOT
Mar 27, 2003 6:36 AM
Is the max psi rating any indication of how strong a tire is?For example would a 700 X 23 tire with a max psi of 130 be structurally stronger and less likely to flat than a tire with a psi of 110? How do manufacturers determine the max psi of a tire?
re: Tire Strength Questionfilly
Mar 27, 2003 9:03 AM
don't know for sure, but a previous poster replying to my question said that the way specialized comes up with their numbers is by inflating a sampling of tires until they burst, and then taking the average of the 50% value of these max pressures. so, by this reasoning, if you see specialized tires with a psi of 110, then their burst psi is approximately 220. so, that's why you should be able to get away with inflating your tires a bit over the labeled psi on the tire. i do, and i haven't had a flat yet (i've only been riding since january, but i've got 1000 miles).
Not really an answerjw25
Mar 27, 2003 9:43 AM
but a thought on max psi ratings. I've seen Mavic-published limits for some rims, of 140 psi. I of course stick to these, as the thought of blowing the brake track off in a race gives me the willies.
And, as a result of my mtb racing, I've come to favor lower pressures both on and off road. I've seen published data that shows a leveling off of rolling resistance as psi increases. Above a certain point, and it doesn't make much difference, and rolling resistance is a small factor anyway, compared to wind resistance.
I'd much rather be more comfortable, and have better cornering traction, than squeeze the last milliwatt of RR out of my wheels.
To try and answer your question, though, I'd have to say no.
Max inflation is based on the manufacturers' method of testing, and includes a healthy margin for error. Pressure can change as temperature rises, or people can and do overinflate.
Punctures, both pinch-flats and sharp objects, will happen regardless of casing strength. It's possible that a more robust casing will be stiffer, and thus resist punctures better, but that's a side effect. Also, puncture resistance tends to depend on the number of layers of casing under the tread, and the inclusion of a more resistant material, such as kevlar. The sidewalls may still be thinner, so the ultimate strength and punture resistance are dependent on different factors.
So, I'd say pick your tires based on their strengths, and don't expect one to do it all. I don't race on training tires, and try not to train on the good rubber.
Don't forget bead blowoff!!Alexx
Mar 27, 2003 10:41 AM
One of the reasons why no manufacturer suggests 150 psig for a clincher is that the bead can't handle it!!
If you really, really need to run such high pressures, tubulars are the only way to go.