Gmc Sierra 1500 Tire Questions/speedometer/pressure

[shwagy357]

I have a 2002 GMC Sierra 1500 w/ P245/75R16 tires installed. However, the info in the door jam only refers to P65 tires. I have found that my speedometer is off, relevant to my GPS. I believe this is due to the difference in tire size. How can I fix my speedometer to display my correct speed?

 

Also, does anyone know how much air pressure is recommended for the P245 tires? Or could someone please point me in the right direction to figure this out?

 

 

Thanks

[Matt_]

What are the size of the new tires?

 

To re-set your speedo you can get a handheld tuner (i recommend Superchips). Or you can get a custom tune.

 

As far as tire pressure, most LT tires are good with 35-40 PSI for a daily driven 1500 series truck. When towing/hauling you can bump the rear up to 50 or so to help stabilize the truck better than the stock P tires could.

 

If you want to do the technical method, there's load vs. inflation charts for LT tires. You find the max load your stock tires can handle at the recommended 35 PSI rating and look at the chart for the equivalent load for your new LT tires. From what i've seen... almost all LT tires can handle more than a 1500 series truck can when inflated to 40 PSI. And thats "fully loaded", for daily driving 35 PSI is usually spot on if you base the pressures off of the curb weight of the vehicle + some extra weight for people & daily cargo.