| [GMCnet] Braking performance of the standard system [message #109175] |
Mon, 20 December 2010 18:07 |
Charles Aulgur
Messages: 78
Registered: March 2006
Karma:
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Gary stated:
Conclusion: A locked wheel has 90%
the stopping power of a turning wheel at 10% slip.
Your conclusion may be correct for most applications but I'm sure
you did not mean that for a locked rear wheel on a GMC when making a
hard stop. Under those conditions there is very little load on the
rear tires that are locked up and just being drug along. Someone
else on the net was wondering if the reaction arm system was needed
on the rear wheels if it is no longer being lifted by the mid wheel.
When I was developing the reaction arm system I thought if I was able
to prevent the mid axle from lifting the rear of the coach that would
be all I needed to do. What a surprise I got when I ran my first
test with the reaction arms on only the mid wheels. The videos
showed there was very little difference in the time it took to lock
up from the previous test in the OEM configuration with no reaction
arm installed. Another surprise I got was the sound of rear tire
screeching. Dumb me didn't know that my video camera was recording
sound. If you run the video frame-by-frame you can tell exactly when
the tire starts screeching in relation to the suspension travel. So
the answer is you can get more increase in braking capability by
putting the reaction arm on the rear wheels then just adding it to
the mid wheels.
Most people know that the rear brakes on a GMC causes the rear of the
coach to lift and the lift is being dome by the mid wheels because of
the CW torque applied to the end of the mid axle suspension from the
brakes. As more brake pressure is added to the mid wheel brakes,
more load is being added to the mid wheels which will allow it react
a greater braking load before sliding. If you believe this then it
shouldn't to hard to understand the opposite affect is taking place
on the rear wheels. The CW torque being applied to the end of the
rear suspension arm from braking has to be reacted my friction
between the road and tire and is a function of how much weight is on
the tire. For every inch-pound of torque added to the end of the
suspension arm, there has to be an equal and opposite decrease in the
amount of torque the tire can react from the road surface. When the
rear tire gets unloaded to the point it can no longer balance the
brake torque, the tire starts screeching and you get flat spots on
your tire. I don't know of a thing that will keep this from
happening other then the parallel linkage suspension provided by
installing the reaction arm suspension system.
Chuck Aulgur
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