Howard - 12-23-2015 at 04:41 PM
I have a Ford F350 7.3 Diesel dually with air bags.
I have a Host 11.5, dual slide cab over that weighs in the neighborhood of 4,500 LBS loaded.
I just bought 4 rear tires, LT235/85R 16 120 rated.
Here is the big question, are you ready?
What should the tire pressure be in the rear? Should both tires on each side carry the same LBS? What about the front, what do you recommend??
I am talking about paved highways, including #1 in Baja.
[Edited on 12-23-2015 by Howard]
David K - 12-23-2015 at 05:11 PM
"I am talking about paved highways, including #1 in Baja."
This should be in the owners manual or in the door jam. If these are larger than stock tire size or very different, then see what the max. air
pressure is ON THE TIRE sidewall, and estimate how close you are to the max weight you are carrying.
The really true way is to do a CHALK TEST. This will show how much or little tire contacts the pavement at that pressure, and guides you to add or
take away air.
If there is an off road component to your question, then a starting point is to deflate about 1/3 for dirt roads and 2/3 for sand. You will need to
adjust as all tires are different.
If you are not familiar with the Chalk Test, here is mine from 2012, on Tacoma World: https://www.tacomaworld.com/threads/chalk-test-dynapro-atm-a...
[Edited on 12-24-2015 by David K]
ncampion - 12-23-2015 at 05:14 PM
That's a little more complicated question than it seems on the surface. Start by taking a look at the Max. load figures that are stamped on the
sidewall of the tire and also the Max. pressure. Do some calculations to be sure your are well within these max capacities. These capacities are
only good at the max. pressure. You probably don't want to run max. pressure, usually about 80% is a good place to be. This then lowers the max load
proportionally. Just be sure you don't overload the tires with too little inflation pressure. I'm not a tire expert but have learned through a
little experience and some research.
cliffh - 12-24-2015 at 09:58 AM
Run tire pressure within 5 lbs of max stated on tire all the way around , check pressure when cold and have a fab trip.
TMW - 12-24-2015 at 10:01 AM
Here is a chart that may help you.
http://www.michelintruck.com/reference-materials/manuals-bul...
All the tires on the same axle should be inflated to the same pressure (PSI). In other words both front tires should be at the same PSI. All four rear
tires should be at the same PSI.
You don't want to under-inflate a tire for highway driving. It will overheat and can blowout. Over-inflating will cause the center of tread to wear
faster. Do not inflate over the maximum PSI printed on the sidewall.
The chalk test DK mentioned above will provide the proper inflation level for even tire wear. Remember if you pull the camper off you should redo the
chalk test
BAJA.DESERT.RAT - 12-24-2015 at 03:45 PM
Hola,
david k...thank you for the chalk test info. i'll do it this weekend.
also, i guess wear that is showing on one side or the other means needing an alignment.
BIEN SALUD, DA RAT
AKgringo - 12-24-2015 at 03:58 PM
Another concern with dual rear wheels, especially with the load you have, is that if even one tire is low the side walls could start rubbing and ruin
both tires.
Do what truckers do to check them. Every time you stop, thump each tire with a hammer, and if one feels different, put a gauge on it!
TMW - 12-25-2015 at 11:18 AM
Tire wear on one side is usually the camber being off. One thing you should consider is when the camper is on it can affect the camber. Camber is
leaning of the tire to the inside (negative) or outside (positive). If the camper is causing the front of the truck to rise that could change the
camber.
I had a 91 chevy and when it was new there was no camber adjustment. Later there was a kit installed. The outside of the front tires always wore
making tire rotation a must and usually led to early replacement. I complained that the guys doing the alignment where not doing it right, maybe it
was the factory setting were not right. Anyway I started doing my own camber adjustments on that truck and the tire wear went away. Most factory
settings call for a little positive camber.
I did a lot of experimenting with different camber setting at the time and if you put a lot of negative camber (tilt inward at the top) the tires will
squeal like crazy around turns, like in the old movies.