What's Up with Your Coach
Wheels?
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Apart from tires, your next best
friend on a coach are its wheels, the connection between tires and axles.
As a routine item, we often look at
the wheels of a coach, but sometimes not in an informed way, a way which may
tell us about what is happening with the coach, bearings, lubrication and
tires.
Part of your check-out before hitting
the road for even a short trip should include an inspection of each wheel.
Even a small rust streak coming from a nut may suggest that a nut may be
loose; since aluminum wheels don't rust, it should be a signal that immediate
attention may be required.
Each time any tire or other
maintenance is performed on your coach, it is important that the wheel itself
is not taken for granted. Any cracks, corrosion or any wear to the rim flange
is a matter of potentially serious concern. Causes of such wear can be as
simple as uneven air pressure on drive axles. Uneven air pressure puts extra
load to the more highly inflated tire, heating it up. If one tire is at 110
lbs of pressure and the other at 100 lbs, then 10% increased load has been
placed on the higher pressure tire. Since most of our coaches are pretty well
loaded up, a ten-percent increase may put the 'good' tire over its rated
maximum. Of course checking air pressure on a routine basis can also detect
such a problem, but wheels themselves can be another indicator of
difficulties.
Rims can have excessive wear on
flanges. Usually this is caused by the sidewalls of the coach being flexed.
Extremely worn rims can actually develop an edge which in turn will cut the
sidewall of a tire. This is more likely found on a fleet coach. However,
there is a gauge which wheel specialists use to check for wear and condition.
The fix for worn wheels can often be rather simple, depending upon condition.
It is critical that a certain minimum flange height is maintained, however, to
avoid tire loss (boom).
Another condition meriting attention
is to inspect the inside of the wheel when tires are removed. Too much
corrosion in the drop center suggests that air lines have too much water in
them or the tires were mounted with a water-based mounting solution.
Extreme heat is an enemy of long life
for coach wheels. Any heat up such as a dragging brake, tire damage or
high-speed run on a hot day with an overload can overly stress wheels. Heat
can also permanently damage a wheel itself. A quick way to determine the
condition of a wheel is to dismount is from the coach, remove the tire and
slowly roll it across a flat surface. It should roll straight and smoothly.
If it doesn't replace it.
Coach owners can keep heat build up
under control. The easiest way, of course, is to maintain proper air
pressure, avoid load and speed maximums for tires. In addition, using a brake
retarder can extend wheel and brake shoe life by up to three times.
Not an insignificant difference.
When changing or adjusting brakes,
insure that it is done on both sides of the coach at the same time.
Some commercial fleet operators are
moving toward larger, 24.5 aluminum wheels from 22.5 steel wheels to increase
heat dissipation and decrease tire changes (an extra inch per side is a big
help).
When wheels are mounted, it is
important that they be very clean; to avoid any damage to an inside wheel, for
example. Some coaches have inside wheel cracks which extend from stud hole to
stud hole, which may have come from improper workmanship or not enough torque
applied to the wheel.
Look carefully at the center of your
wheels; if you have radiating lubricant smear, which looks rather 'spidery' it
may be that you have a worn or improperly installed seal in the bearing. Any
unusual appearance of lubricants, dusting or wear should perk up your interest
right away.
Watch as tires are mounted on your
coach. They should be first under-torqued with an air impact wrench and then
brought up to 450-500 lb range with a torque wrench. After just 50 to 100
miles, they should be checked again.
Finally, when replacing either studs
or cap nuts, any qualified installer should only use Grade 8 rated material
(metric 10.9). If the box containing the parts is not marked specifically as
Grade 8, don't put it on your coach.
Be mindful that tire extensions often
do not provide an accurate measurement of tire pressure. When you are
checking tire pressure, take off the extensions. There have been cases where
as much as 30 lbs of difference was measured with and without the extensions.
Inside drive axle tires are just as important as outside drive axle tires;
they take a bit more trouble to check; and wheels even tougher. It may be
alright with your service people to actually be there and check wheel
condition when your coach is being serviced.
We all want to have bright, shiny
wheels going down the highway. That's the right way to do it. By following a
few common sense tips on maintenance and care of wheels, we can do it with
peace of mind and safety, too.