QuestionQUESTION: My 2000 Silverado 4x4 SB Regular Cab came with P245 75R16 tires when bought new. I don't know what the original max tire pressure was, but the door placard says 35 psi front and back. I have now put P265 75R16 tires on it. The maximum tire pressure on the new tires indicates 44 psi. Do I still stick with the original 35 psi front and back? Won't that seriously underinflate the tires? The vehicle is stock, except for the addition of a camper shell. You guys are the greatest! Thanks...
ANSWER: Mike,
The "max" pressure is just that - a maximum.
But the usage pressure is what the vehicle manufacturer put on the placard. The tire manufacturer has no way of knowing what vehicle the tire is going on, so he can't indicate what the pressure should be.
---------- FOLLOW-UP ----------
QUESTION: Yes sir, I understand what max pressure means. Sorry, maybe I didn't phrase the question properly. Does the original vehicle manufacturer's usage pressure (35 psi front/back) remain the same even though I've gone up a tire size and the max pressure is now more? For example, would I stick with 35 psi usage pressure even if I had LT's with a max pressure of 60 psi? Sorry for the confusion...or, more likely it's just me.
ANSWER: Mike,
"..... Does the original vehicle manufacturer's usage pressure (35 psi front/back) remain the same even though I've gone up a tire size and the max pressure is now more?....."
No, on account of the tire size, not because the pressure on the sidewall of the tire is higher.
"........For example, would I stick with 35 psi usage pressure even if I had LT's with a max pressure of 60 psi?........"
No, and since you added LT's to the mix, I'll tell you it is way more complicated than that.
But the simple answer is that the pressure you should use should create the same load carrying capacity as the vehicle manufacturer specified. Tires are primarily about carrying the load.
So let's start over, and this time it is my fault. You gave me all the info, but I was pretty superficial with the answer.
If your vehicle came with P245/75R16's inflated to 35 psi, using a P265/75R16 allows you to use 27 psi.
But you may have a larger problem. My book says that your vehicle came with 6.5" rims and P265/75R16's require a minimum of a 7" rim. Please check your rims out to see if my book is correct.
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QUESTION: Usage pressure 27 psi, got it. Ignore the LT comment, it was just an example. I've checked the placard and my rims are 16x6.5J. I've had the 265's on there for almost 2 years now with no problem. Is there an issue I need to confront the tire guy about? Again, thanks for your time.
AnswerMike,
If you want to tell the tire guy about the rims - well, I just think you will be wasting your breath. They should have checked before mounting the tires, but until something goes wrong, there really isn't anything to argue about - so they won't be receptive.
