Quote:
Originally Posted by Tahoe_Hybrid
the standard PSI is 38PSI for GM for passenger cars
I was talking to a so called mechanic (one that claimed to be) he said he uses 29PSI and that air expansion will make it higher which is true but why risk a blow out when the side wall fails because it's under inflated..
that is what ford said to use 29PSI shortly after they had tires failing left and right..
if you have it at 40-44PSI the max side wall there is no increase or heating of the tire or heat cycling the tire.. after drive for an hour at 40PSI the tire is still cold to the touch PSI stayed the same
with the tires at 32psi the PSI increased to 36PSI from internal heat expansion
|
Sorry, but most of this post is incorrect.
If I look at Tire Guides - a publication that summarizes the tire placard information for easy reference - GM trucks, vans, and SUV's use 35 psi for P metric tires (when they use those). There are a few exceptions.
I was going to say that GM cars tend to use 30 psi, but a quick perusal of the latest Tire Guides says that that is no longer true - that the recent tire pressure specifications are all over the ball park (range 30 to 36 psi).
The post has an indirect reference to the Ford/Firestone situation some 20 years ago - and 1) The failure was NOT in the sidewall. It was a "Belt leaving Belt Separation" (commonly called a tread separation) and 2) The cause was a combination of the tire design, and the manufacturing, not the inflation pressure. I go into detail here:
Barry's Tire Tech
There also appears to be a misconception by the mechanic that the max pressure is close to the burst pressure of the tire. Tire burst pressures are on the order of 2 to 4 times what the max on the tire says.
Lastly, it was stated that high inflation pressures do not generate pressure buildup - ah ….. not exactly.
There is pressure buildup any time a tire is operated. The question is how much.
Normal city street driving doesn't generate much (1 or 2 psi), while freeway driving generates more (up to 3 psi). Obviously using a higher than placard pressure would reduce the amount, but it is not zero.
Most pencil style tire pressure gauges measure in 1 psi increments, so 1/2 psi build up would be undetectable by those.
Hope this helps clear things up.