QuestionQUESTION: I have a 95 Ford Bronco and have 31-10.5x15 Uniroyal Cross County radial tires on it. The door jamb says for the original P235/75R15 XL tires the tire pressure is 35 front and 41 rear. Can you help me convert this to the proper PSI for the new size? Thanks....
ANSWER: Patrick,
Yes, I can convert it..........Oh, you mean you would like me to do that?
It turns out that earlier years of Bronco's came with the same tire size on the vehicle placard and at the same pressure.....
AND
They also came with the size you want the information on - and those placards said to use 40 psi - which means they were not using a load equivalency method to determine the pressure.
If I do the math and use load equivalency, I get 37 psi front and 42 psi rear - and maybe Ford was thinking that having the same pressure would be easier to remember. Or maybe they had slightly different version of the vehicle and this resulted in different loads on the tires. I don't know, but there you have it.
---------- FOLLOW-UP ----------
QUESTION: Thanks for the info. What's the load capacity for the original P235/75R-15's at 35 and 41PSI? I can only find on the net that a P235/75R-15 (non XL) is 1843 at 35PSI and am curious as to what the XL rates at.
AnswerPatrick,
You don't need to worry at the front - they're the same.
The 41 psi spec on the rear is the problem. And honestly, if you promise never to put a lot a stuff in the back, you could get away with standard load tires at 35 (or a bit more) psi.
I am only a bit concerned about the handling when using a lower pressure, but the risk is relatively small and I've just warned you to be careful about this, so you should be able to sort this out yourself.
