[MV] more on super singles
Cougarjack@aol.com
Fri, 26 Mar 1999 01:52:18 EST
list,
>From the stuff that's been presented so far on this subject, I can clarify a
few things...first, the singles that were tested in the test I referred to
were all 14R-20 to 16R-20 tires of a very soft gummy compound. Single tire
weights were almost equal to the duals. In the case of a few designs, they
were actually greater. The wheels were specially made drop center, for the
necessary clearance, and this offset was the cause of most of the trouble.
Even with the offset hubs and wheels, there was still chafing at full turn
under some conditions. There was also rub on suspension bottoming as I
recall.
The appearance of the truck with these wheels and tires mounted was that of a
much wider track truck. I don't believe that 11R20's would cause the same
trouble, because the wheel offsets are near stock. The tires that Joe
pictured are also a very different aspect ratio that the ones that were
tested. I don't think I would be as reluctant to try the 11R20's on stock
offset wheels. There would be little basis for that fear. I also believe that
radial tire engineering has come far in the 30 years that have passed since
the test. Sidewall strength is now suited to truck service, and rubber
compounds are much better. Just remember the caveat that radial tires flex
differently than bias plys, so handling and load transfer will change.
Radials tend to oversteer compared to similar bias plys, so some adjustment of
driving technique is called for.
Tom Bauer is correct in that the bolt holes on both sides of the hub are the
same, and the bearing cups are the same outer diameter. This is one of the
changes that we had to make in order to mount the wheels. Note that in our
test, even with the reversed hubs, due to the greater tire widths we were
using, the load offsets were still greater than stock.
I did not mean to imply that the M35 truck was in any way unreliable or prone
to roll over in normal service. I believe it is one of the finest designs ever
to come out of the military. A tactical truck is of necessity higher with
more ground clearance than civilian designs, and there is a lot more heavy
material above the frame rails, so suspension stability becomes more important
in such a truck. The M35 in particular has a relatively narrow track for a
truck its weight and size, and the oversprung suspension coupled with
understeer in a stock truck means that the rollover threshold is always
nearer than other designs. This is mitigated by the fact that the M35 was not
intended as a highway hauler, and was not equipped for high speed dodging in
city traffic. Offroad with a heavy load and a tow, it is surefooted and
unstoppable. The tires we tested did little to enhance stability, and I
attribute a lot of the trouble to that fact alone. Those of you who inferred a
faulty design or other criticism from my first post...please relax...it's a
good safe truck, and a proven design. You also must understand that the army
doesn't mind destroying equipment in its quest for better trucks. Most of
these tests run by AMC are destructive in nature....a lot of data can be
obtained quickly by pushing equipment to the point of failure. The injuries
and deaths are never intended, but military equipment is dangerous, and is
built for a very narrow purpose.
The results of all the tests that AMC does are a matter of record, probably
retrievable by the public through some protocol, and contain some very
interesting experiments. It was my luck to be connected with an ill-fated
one.
Nick
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