Tire inflation

I have a 3/4 ton GMC 4X4. When carrying heavy loads should I adjust the tire pressure?

See what the owner’s manual has to say.

Personally, if the loads were heavy and often, I’d simply keep the pressure on the high side of the recommended range. If they were rare, and short distance, I’d keep the pressure on the low side for a slightly better ride. If they were rare but long distance, I’d keep it on the low side normally and adjust it to the high side for the trip.

The owner’s manual didn’t survive the transfer of ownership. “friends and loggers” are offering the opinion that way over inflating the tires keeps them from getting too hot and reducing drag. We just got new Firestone tires and I have images of the old Explorers and their exploding rubber.

We don’t over load often, but can get more than a ton of hay, firewood or gravel into the bed without much problem, then need to five 45-60 minutes.

Frankly there is no single answer to this one. Generally full loads will call for higher pressure. However how much if any depends on the truck.

If no one comes up with the answer, your might try doing some on line searching on tyre web sites and see if you can find the original recommendations.

Note: DO NOT go over the maximum rating indicted on the sidewall of the tyre.

" Note: DO NOT go over the maximum rating indicted on the sidewall of the tyre."

What a great segue to a tire safety note. It has been noted several times on this board that the tires should be inflated to the level listed on a tag affixed to the door jam, under the hood, or in the trunk. This is less than the maximum safe pressure on the tire sidewall. Since this is a safety issue, I thought I’d bring it up for those who have not seen it before. As we used to say in the steel mill, you can’t talk about safety too much.

Yes, the higher the weight the higher the pressure should be. How much? I don’t know. It depends on the tire. You can inflate the tires to the max pressure on the side walls. At some point the handling will get squirrely when they have too much pressure.

Does this thing have real truck tires? In the olden days the owner manuals had lots of information about inflation pressures wrt load. That kind of information is too confusing for most drivers today. What is the max inflation pressure for the tires? What year is your Exploder?

Go here and follow the links to download a manual:

This is an example of the type of charts you used to be able to find in LT manuals:


I will make up some very round numbers in pounds. Take a truck that weighs 5000. The rear axle has 2000 on it and the front, 3000. You add 2000 payload. In doing so you add 1500 to the rear and 500 to the front. That is a total of 3500 rear axle and 3500 front. Note the charts are for weight of the axle END.

From the LT225/75R16 LRE chart you can have minimum pressure, 35 PSI, in the unloaded condition. When loaded, you should have about 40 PSI all the way around because you have 1750 at each axle end.

With a little effort, you should be able to find a chart specific to your Exploder. Maybe a tire marketer can help.

You should. Your tires will say the max pressure and it will probably be over 40 PSI. You should max them out for a heavy load. The maximum rated load should be enough to justify it. The high pressure will keep the tires from blowing out.

Another safety note:

The OP said he was putting over a ton occasionally into a GMC 3/4 ton truck. If I remember right, a GMC 3/4 ton truck has a load carrying capacity greater than 3/4 ton, but this ought to be checked - and if there is any question about the payload, the truck ought to be weighed when loaded.

Below BeadsandBeads mentions tire load tables. Folks need to be aware that these load tables are maximums for ideal conditions. This was one of the issues exposed during the Explorer / Firestone thing. If you are using these load tables, it is a good idea to have 10% to 15% excess capacity.

When all else fails, read the instructions!

In this case, the instructions should be on the door jamb of the driver’s door. Alternatively, there could be a label with inflation directions on the gas filler door or on the inside of the glove compartment door.

And, since there will inevitably be other issues, you really should buy an Owner’s Manual. Try e-bay.