Just bought a 2006 F150 STX 4x4 Extended Cab with 6.5' bed.
It has 20 inch rims with 27560r20 Cooper Discoverer H/T Plus Tires.
What should I be running for tire pressure on this set up?
Thanks!

 

Unfortunately the Cooper web site does not list the max pressure. It does list it as a P series extra load, so I am assuming max pressure is 50. Cooper states that it handles 2998lbs at max, meaning with the 10% reduction due to use on a light truck, max load is about 2700lbs. For that tire you should be using a minimum of 35, 38 may be better. Do not go below 35. Keep an eye for improper tire wear and adjust accordingly. If you tow, you can go higher while towing, and should. That will help with the sidewall flex. If the max pressure is different than what I assumed, post back with the numbers on the tire. xxxx lbs at xx psi cold.

 

What does the door jamb sticker say to run?

 

Doesn't matter, those are aftermarket tires. Also Ford does not put XL P series tires on. They are either SL P series or LT.

 

The door tag is for 275/55/R20 and the pressure is 35psi. Guess I should have looked there first. I didn't know that size tire came on the truck. I forgot to mention, it is the patriots edition. Thanks for your responses!

 

It does not matter if the tires are the same size or not. What matters is the load range and tire type. There are 5 different load ranges that can be used on an F150. P series standard load, P series extra load, LT load range C, LT load range D, and LT load range E. Each would have a different recommended pressure.
Personally for the extra load tire you have now, I would use 38, not 35. If you do stick with 35, make sure that if you haul anything or tow anything to bump it up.

 

What the hell kind of tire doesn't have this info listed on the tire itself, on the sidewall? That's strange. Patriots edition makes a difference, cause I was wondering what 2006 STX has ever come from factory with 20" wheels!

 

What is on the side of the tire is the max weight and pressure, along with load range. It does not have the pressure recommended for that tire on a particular vehicle.
Even for the exact same tire, one on a Ranger and the other on an F150, it would need a different pressure for each truck.

 

Oh, I thought he meant they didn't even have that. I just do 38-42 for my 44 max tires.

 

Thanks for all the help!

 

In actuality, your tires, P series standard load, only need 35 psi. That is where those tires get the max load carrying ability. Anything over that is only for sidewall strength. The OP's extra load get their max load carrying ability at 41psi, but being those tires have a higher load carrying ability than a standard load is why I suggested 38.

 

Huh, thanks for the info!

 

Here you go, info on the different load ranges and tire pressures. One thing they do not mention here is that some LT load range D tires have a max pressure of 50 psi (similar to LR C), and some LR E tires have a max pressure of 65 psi (similar to LR D). In all cases, unlike P series tires, LT tires get their max load carrying ability at the max pressure listed on the tire. Also when looking at the tire info on a P series tire for max load carrying ability should be reduced by 10% when the tire is used on a truck, mainly due to the higher center of gravity. The P series tires don't have the sidewall strength of an LT tire.

http://www.tirerack.com/tires/tirete....jsp?techid=55