Tires: Bigger tire and proper inflation, oe tire size, narrow wheels

Question
I just bought 285/75/16 Goodyear duratrac tires for my 3/4 ton truck. The card on the door panel recommends 55 psi front and 80 psi rear for an oe tire size of 245/75/16 load E. What tire pressure do you reccomend I use on the 285's load E as well. Thank you for your time.

Answer
John,

There are 2 rules:

1)  Match the load carrying capacity

2)  If you can match the load carrying capacity with a lower inflation pressure, match the spring rate by using the same inflation pressure.

So let's do the math:

In order to carry the same load an LT245/75R16 does at 55/80, an LT285/75R16 needs to use 40/58.

Rule 2 says to use the original inflation pressure.

One last consideration:  Many 3/4 ton truck use 6.5 or 7" wide wheels - and an LT285/75R16 requires a minimum of a 7.5" wide wheel.  You should check your wheel widths, because operating a tire on a narrow wheels tends to cause the tire to follow the grooves and ruts in the road and may cause some sensitivity to cross winds.