duals, are properly spaced from each other. If the duals touch sidewalls, they won't last and
are a hazard. (If you do decide on bigger or wider tires, work with a pro. Substituting
LT235/85R16 tires in place of 7.50-16 tires is probably not going to work in the duals
position without changing rims too – they would be too close together.) By the way, a bent
rim can cause problems, but should be caught when you have the tires balanced. Mention
that you want this checked to ensure someone with experience looks at the rims instead of
the new guy.
Current load and inflation information for popular auto tire sizes may be obtained from your
local tire dealer, the manufacturer's web site or tables may be obtained free by sending a
stamped, self-addressed business-size envelope to "Tables," Tire Industry Safety Council,
Box 1801, Washington, D.C. 20013. See the Appendices in this document for an extract
from the P Chassis manual with inflation info. The chart for tire inflation in one of the
appendices is from the service manual and is not current (it was published in 1995). It is
provided as a general guideline – but exact inflation pressures should be obtained from your
tire manufacturer for your brand and model of tire.
Don't forget to torque the wheels correctly using a torque wrench – NOT an impact tool.
8-bolt wheels (9/16 bolts) get 140 ft. lbs.
5-bolt front wheels and 10-bolt rear wheels get 180 ft. lbs.
We're still not quite ready for that alignment.
There are two more items to check. Ride height and frame angle. Both affect the caster that
will be set during the alignment. Without these numbers, you CANNOT come up with a
valid CASTER setting. This is the one that most frequently is set incorrectly.
Ride Height
Ride height is checked at four points. Tolerance for manufacture of the springs is ± ½ inch.
If the side-to-side measurements are not equal, or within the tolerance of 1”, some work
needs to be done. Also, the front-to-rear ratio for each side should be close to the same.
However, there are steps that can be taken to fix or correct these measurements quite a bit.
Ride height measurement points are specified by the manufacturer. On some vehicles, it is
from the frame to the ground, a specific point on the underside of the body to ground, or
between components as specified by the manufacturer.
The measurement for the P Chassis is taken as illustrated in the next diagrams. The best
circumstance is to disconnect one end of each shock absorber before making this check
(good time to check the shocks too) and the motorhome must be on an absolutely level
surface. If the surface is not perfectly level, you can shim to level by placing squares of
plywood under each wheel until the tops of the plywood at each corner are at the same level
Main Body Page 10 of 38 Total Pages
