Thread: Tire question
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Old 12-09-13, 12:48 PM
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cyccommute 
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Originally Posted by rekmeyata
Pros have been using higher pressures for a long time and I stated that, however lately they have been reducing their psi.

Cyccommute I don't want a running argument with you, I don't know why your tires would have blown off unless they were below the tire manufacturer's minimum psi requirement which a person does have to look at before they put 25 psi in a tire. Or maybe your air pressure gauge is incorrect. Whatever the reason it doesn't matter, like I said before you use whatever psi you want and lets leave it at that.
I agree that pros (and most other cyclists) have been using high pressures for a very long time but it's not because of any charts they were consulting. The pressures that are run in tires are largely a matter of guess work. Even now, I don't think there is anything definitive about tire pressure. Even the manufacturer's recommendations are largely based on guess work. Heine and Berto's work is an attempt at a definitive method but the model doesn't fit real world experience for the reasons that I detailed above. If their model worked, then people who weigh next to nothing could ride with the kinds of pressures that they recommend. A lightweight person could ride with 25 psi in their tires and not have any problems. On the other hand, I should suffer some detriment to not running 165psi in my rear tire on my road bike. I've never notice that 110 to 115 psi was causing my any issues and I wouldn't want to ride with a tire at a higher pressure. I see no benefit.

The problem with Heine's model is that it is wrong. That's not necessarily a bad thing because, as George E. P. Box said, "All models are wrong. Some are useful." Heine's model is wrong (as are all models), his just happens to be wrong enough to not be useful.


As for the blow offs I experienced, it wasn't the pressure gauge since the tires had been pumped to pressure with 2 different pumps and the tires blew off 2 wheels twice. It wasn't really the load since the load wouldn't have made that much of a difference in the tire pressure. It's a systemic problem I've had with Continentals. I've had them blow off on Lolo Pass in Idaho just after inflating to the recommended pressure. I've had them blow off while sitting on a car rack. And I've had them blow off that 4 times in Texas. I eventually found a pressure that I could ride them without blowing off the rim...it was around 60 psi...but the pressure was so low that I had to be extremely careful with bumps and pot holes to avoid pinch flats. I don't run that brand anymore because of the many, many issues I've had with their tires.
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