I bought a 1998 Dodge Ram 1500 4X4 Quad Cab recently. Which came with
LT 285 75R16 All Terrain T/A KO tires, after driving for a couple of months
I noticed tires looked low. When I had the oil changed I asked them to
check the tire pressure. They told me that my tires where properly inflated
at 35 PSI. I went by local tire company to have them checked again as they
still looked low. The guy there told me he added 2 PSI to each front tire
back rears were fine. Tires actually say 65 PSI. When I questioned him
about this he told me they were fine. I understand that the Door Panel of
the truck says 35-40 PSI, however these are not original tires, they are
oversized. Could someone shed some light here?
Thanks in advance,
This can be a difficult problem. The best gauge of proper
tire pressure is tread wear. But if you guess wrong, you'll wear
out the tires too soon.
You already know these are not stock tires, and you know the
sticker in the door frame is useless. They are heavy duty truck
tires, designed to carry a maximum load. Look on the sidewall,
and you'll see lettering that says Xpsi at Y pounds. Calculate
how much of a load your tires do have, and devide by 4. That's
about how much weight is on each tire. Now look at what your max
tire pressure is. Whatever the percentage of max load you have,
that's the percentage of tire pressure you should start with.
That is a pretty crude calculation because it doesn't
include front to rer bias, cross weights, etc. But it will get
you in the ball park.
Now go drive the truck for a while. Long enough to get the
tires good and warm. Use an infrared thermometer and check the
tire temp in the middle and ech side of the tread. Should be
roughly equal when the pressure is right.
If you don't have a thermometer, you can use the chalk/paint
method. Not nearly as accurate but a whole lot cheaper and
probably close enough. After the tires are warm, put some paint
or chalk across the tread. Roll foreward just a few tire
rotations. You can see where the chalk/paint is scuffed off.
Again, should be equal across the tread pattern when the pressure
Well, yes and no. The stock rims will handle tire pressures
of 65psi, and probably more. They are pretty sturdy.
However, take a look again at the weight rating on the tire.
Look at how much weight the tires have to be carrying to reach
their max. Probably far more than your truck can carry safely.
That means - as far as the tires are concerned - you have a huge
safety margin in weight capacity.
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