The whole thread about tire blowouts is sort of shocking to me. When is the
last time you had a blowout on a four wheeler (or heard about one)? Semi's
roll up millions of miles and although they occasionally shed some freeway
alligators, the casings are usually good enough to retread. And
semi-trailers going down the highway don't seem to have any wiggle-waggle
going in and out of the ruts. Of course these are apples and oranges
compared to our coaches, but it does cause you to wonder about the
differences. One big difference is the rear wheel suspension- our are
independent and theirs are tied to an axle which keeps the tires on both
sides tracking parallel. After about 5,000 miles on my new tires and Alcoa
wheels I'm seeing a slightly uneven wear pattern from one tread section to
the next. This caused me to suspect the alignment- so I made a fixture to
measure the situation. Without boring everyone with the details, I made a
track that is spaced out parallel to the frame rail. From that I mounted a
pivoting arrangement that picks up the outer flat area on the wheel and
using a 90 degree shape, points down the rail 46 inches to a scale graduated
in tenths of a degree. In my case the right forward wheel was pretty close-
towed in about 0.15 degree, but the rear was pointed out 0.35 degrees. On
the left side, again one wheel was in about 0.1 degree and the other out 0.4
degrees. At first, I thought that wasn't too bad, until I did the math and
concluded that the two worst wheels collectively point 0.75 degrees apart
and that means they scrub about 1.2 inches for each revolution of the tire.
I'm in the process of having them realigned right now, so I can't say if
this will make any difference in driveability, but I do expect an
improvement in tread wear and they should run cooler. My guess is that heat
is the biggest enemy of tire life. Heat increases with over-load,
under-inflation, high speed, out-of-balance, road hazards and mis-alignment.
I also was interested in the comments by a net-member a while ago who
reported much worse road wander with new tires and Alcoas. Could that be
related to the stiffness of his new Load Range E vs old D's? It makes me
wonder if lateral flexing of the side walls helps or hurts driveability.
Clark Searle
Mt. Pleasant, MI
last time you had a blowout on a four wheeler (or heard about one)? Semi's
roll up millions of miles and although they occasionally shed some freeway
alligators, the casings are usually good enough to retread. And
semi-trailers going down the highway don't seem to have any wiggle-waggle
going in and out of the ruts. Of course these are apples and oranges
compared to our coaches, but it does cause you to wonder about the
differences. One big difference is the rear wheel suspension- our are
independent and theirs are tied to an axle which keeps the tires on both
sides tracking parallel. After about 5,000 miles on my new tires and Alcoa
wheels I'm seeing a slightly uneven wear pattern from one tread section to
the next. This caused me to suspect the alignment- so I made a fixture to
measure the situation. Without boring everyone with the details, I made a
track that is spaced out parallel to the frame rail. From that I mounted a
pivoting arrangement that picks up the outer flat area on the wheel and
using a 90 degree shape, points down the rail 46 inches to a scale graduated
in tenths of a degree. In my case the right forward wheel was pretty close-
towed in about 0.15 degree, but the rear was pointed out 0.35 degrees. On
the left side, again one wheel was in about 0.1 degree and the other out 0.4
degrees. At first, I thought that wasn't too bad, until I did the math and
concluded that the two worst wheels collectively point 0.75 degrees apart
and that means they scrub about 1.2 inches for each revolution of the tire.
I'm in the process of having them realigned right now, so I can't say if
this will make any difference in driveability, but I do expect an
improvement in tread wear and they should run cooler. My guess is that heat
is the biggest enemy of tire life. Heat increases with over-load,
under-inflation, high speed, out-of-balance, road hazards and mis-alignment.
I also was interested in the comments by a net-member a while ago who
reported much worse road wander with new tires and Alcoas. Could that be
related to the stiffness of his new Load Range E vs old D's? It makes me
wonder if lateral flexing of the side walls helps or hurts driveability.
Clark Searle
Mt. Pleasant, MI
