I just bought a used 2007 Silverado. The door sticker lists P265/70R17 as the stock tires. It came with 275/70/R17. The sticker suggested 35PSI for air pressure. The dash tells me the current tires are at 41PSI which I assume is reasonable but I don't know how to determine if it is optimal. I've done a bit of web surfing but remain unsure. It's a crew cab Silverado 1500 with a Leer topper, LTZ. I'm also quite puzzled as to how the car knows that the tire pressure is. I'm upgrading from a 93 4Runner that didn't even have air bags so this is quite a dazzling change in cars....thanks in advance. If this is a reasonably active forum I think I'll have a fair number of questions...what is "air conditioning"...where is the clutch pedal.... why does it go so fast with my foot on the floor...

 

Well, I can only speculate, as I haven't had any experiences with tire pressure monitors (they're located inside each wheel). While you drive, your wheels and tires get hotter from friction and your brakes. This will increase pressure too. So if your vehicle tells you that you have 41psi, and you're obviously inside the car, so I can assume you looked at the psi after you've been driving for a bit.

The best way to get your pressure is with a tire gauge, and with the wheel cool and not driven on for a while. I'd run stock PSI in those tires.

Welcome to the forum!

 

If you look at you tire valve stems you will notice they are short aluminum stems. Those are your tire pressure sensors, this is how you truck can read the tire pressure. The recommended tire pressure on the sticker is the recommended tire pressure for the factory installed tires. What is important is what the load rating on the new tires is and what the max pressure is on the sidewall of the tires that are on the truck. 35 psi is the most common pressure for standard rating tires. If you have a high rated tire such as a load range E tire then you can safely put up to 80-90 psi in most cases. For a standard tire it is usually rated for a max of 35 psi.
Now if your tires that are installed are standard tires and have a max rating of 35 psi and you run them to high of pressure it is not only unsafe but it will wear the center of your tires tread due to the tire ballooning due to the excess pressure.

 

In my limited research on tire pressure I found a thread that explained that the rating on the tire sidewall was the absolute Max tire pressure and was cautioned to NOT inflate the tire to that pressure. It further explained that the recommended pressure would be found in the door sticker. I'd never thought about that but indeed on these BF Goodrich tires the Max Pressure suggested on the sidewall is 80psi. The door jam sticker shows the original tires were P265 70/R7 with a recommended inflation of 35psi. That got me to wondering if these E rated LT275 70/R17 tires should be inflated to 80lb (seems high) and my initial reading on the net implied I should not inflate them to that point and wondered what the actual proper inflation would be for them. I checked them again. They are BF Goodrish Baja Champion, E rated, Max 80psi, 9ply (5 tread +1Nylong + 3 sidewall).

 

The kind of tires you have are made to carry a heavy load and the 80psi max is the inflation at the max rated weight. You should be able to find out what that max weight is. Say it is 2600 lbs. @ 80psi. The door tag would be specifying the 35psi for a "normal" load of something around 2000 lbs. on the rear axle or 1000 lbs. on each tire. Between the normal weight and the maximum weight there should be a table giving the amount to increase the tire pressure. As a sample, here is a Michelin chart:
Michelin Americas Truck Tire Load & Inflation Tables

I run 42 PSI front and 40 rear with no load except passengers and a truck cap. I think that is best for the tires as well as gas mileage. If I carry a heavy load, I increase the rear pressure accordingly.

Gerald

 

The new tire pressure sensors look like normal valve stems on theses newer vehicles. I would run the tires at what the door sticker says. If you inflate too much the warning will come on as the spec is set in the door lock reciever. This spec can be changed by the dealer with the tech2. Probably for a fee. You set up the module up as tire size and pressures from a list in the tech2. My opinion is 35 psi would ride and wear the best.

 

Thanks everyone. Forums like this are fantastic.