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Tow Truck Tire Trouble

To: autox@autox.team.net
Subject: Tow Truck Tire Trouble
From: dg50@daimlerchrysler.com
Date: Mon, 17 May 1999 14:21:41 -0400
WHY can I not go to a Pro and not have An Adventure on the return trip?

Coming home from Peru, about 9km north of the I69-US24 intersection, there is an
eash-shattering KABOOM! from my right-front tire, and suddenly I'm wrestling a
tiger. I manage to get the truck stopped and pulled over on to the shoulder, and
all the shiny surfaces are still pointed skywards.

A chunk of tire about a foot long and spanning the tire bead to the tread
shoulder is completely gone, blown clean off the truck, and the flailing remnant
of the tire has done a NASCAR bodywork job on the inner fenderwell. The rest of
the truck and trailer seems fine, although both occupants need a change of
underwear and a defibrilator.

How lucky can you get, though, to have the _inside_ tire go (not the one exposed
to traffic), with enough shoulder room to move over, on a beautiful day, with a
full complement of tools in the truck? The cop who pulled over to offer his
assistance was slack-jawed agape as we watched me jack up the truck with a
couple of pumps of the hydraulic jack, spin the wheel nuts off and on with our
tire change drill, and beat the fender back into shape with a body hammer.

What was bothering us though was how hot all the tires seemed, so completely
opposite the drive down (done, admittedly, at night and in the early morning).
So we pulled into the first rest area to check the tires out.

All the trailer tires were hot to the touch, with the left-side tires the
hottest. All the truck tires were warm to hot, with the spare we just put on the
only exception - it was cool.

Now on the drive down, I had used 4 links of chain in the weight-distributing
hitch, and the truck, while drivable, was very "busy"; floating and hopping
about. It also had a noticeably nose-up attitude. To try and counter it, I had
set up the hitch with 3 links of chain, to try and jack more weight into the
truck and get the nose down. It made the truck drive much nicer, but with all
the tires (inflated, by the way, to about 43 PSI cold all around, so they
weren't underinflated) seemingly on fire, I took that link out of the hitch, let
the tires cool off, and then drove to the next rest area.

At the next stop, the truck tires were still pretty warm, with the left being
hotter than the right (and that dammed spare still dead cold) and the trailer
tires were still scorching, particularly on the left. Looking at the trailer, we
noticed that the car was offset about 6 inches left, so we drove it off and put
it back on closer to center.

At the next rest stop, the tires felt cooler, although they were still pretty
warm. Tired of playing around, I broke out the pyrometer, and started taking
temperatures. The truck tires were at about 109 degrees (ambient was 88 degrees)
with the exception of the right front (the former spare) which was 99. The
trailer tires were about 115-120 depending on where on the tread I measured, but
the left/right temps were now about the same.

Is 120 degrees really hot, or is that normal? Hot pressures were about 49 PSI in
the trailer (1 PSI _below_ the max pressure in the sidewall), and between 47-52
in the truck tires.

The trailer tires are proper ST trailer tires, and fairly new. The truck tires
are "P" tires, and of unknown age, although rated for at least 2000 lbs each -
except for the front 2, which were "extra load" tires rated for 2400lbs each.
(Including the one that blew!)

Today we are buying 5 new "LT" tires to replace the mystery-age tires on the
truck, but I wonder if that's enough. Was I a victim of an old tire, or of my
own mis-configuration of the truck?

What pressures should we be starting at? What hot pressures are too high? What
temperature is too hot? Was I just being paranoid on the way home? Is a helper
leaf a better way to lift the sagging rear end of the truck, (it's a little low
even with the truck empty) instead of trying to jack more weight into the truck
with the hitch?

I _really_ don't want to go through that again, especially not at night, in the
rain, alone, on a road with no shoulder. I need to fix this now the RIGHT way.

Any suggestions?

DG



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