Tires: Tire Pressures, 5th wheel trailer, sierra 4x4

Question
I have a GMC 1500 Sierra 4X4 5.3V8 with 285/75/16 BFG All terrain TA Load range C tires. What pressure should I use pulling a 6000 lb 5th wheel trailer?
Thanks

Answer
Lawrence,

There are a couple of issues here.

First:  Is the trailer you are hauling within the limitations specified by the vehicle manufacturer.  This is important not just because of the load on the tires, but also because of the stress on the brakes, frame, and drivetrain of the truck.  If it is not, then what information is available on the allowable loads in the truck become guesswork - and so does the issue about inflation pressure.  So please check with GM to be sure of this.  To give you a reliable and safe answer, the truck can not be overloaded.

Second - assuming the trailer is within the towing limitations of the truck - the starting point is the vehicle tire placard. It lists the original tire size and the proper pressure for that size.  The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.

BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

One word of caution:  Some trucks use tires with the letters "LT" in front of the tire size - and some trucks use tires with the letter "P" in front of the tire size - and some trucks use tires with the letter "C" after the tire size.  You should not use "P"'s in place of "LT"'s and vice versa.

For this situation, you should be sure the pressure on the sidewall equals or exceeds that pressure on the placard.  If you do this the issue about the letter "C" in the sidewall will take care of itself (which is not true with "LT"'s vs "P"'s.)

If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated.  The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copyright laws.  However, I have a copy and would be glad to do the calculation, but the starting point is the vehicle placard: Tire size and inflation pressure.  

So post a reply with what is listed on the vehicle tire placard - and please include the letters in front of or behind the size.  BTW, the information you gave me tells me the BFG's are "LT"'s.