| Re: [GMCnet] Front suspension geometry [message #124645] |
Thu, 05 May 2011 07:35  |
Gary Casey
Messages: 448
Registered: September 2009
Karma:
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Senior Member |
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Hope it's okay if I changed the name of the thread. I'll give a theoretical
answer to Rob's question about suspension geometry. With the upper arm angled
up compared to the lower arm, the wheel will change camber with suspension
travel. It will go to negative camber in jounce (wheel going up) and positive
in rebound (wheel going down). This is typical of more modern vehicles. As
usual, everything is a trade-off and this is no exception. Camber change during
suspension movement will potentially induce a reaction to bumps where a positive
bump will tend to push the front of the vehicle away from the bump, making it
possibly a little more "jittery" on bumpy roads. On the positive side,
roll-induce understeer will be reduced as the tires will "roll" less than the
body and therefore be better able to support the cornering loads. A long time
ago Buick advertised that their upper arms were angled down, making the wheel go
to positive camber in a bump, and they said that this "pulled" the car toward
the bump, making it more stable. Of course, their cars cornered like pigs!
In my opinion the upward angle of the upper control arm is a good thing, but not
by much. I wouldn't worry about it one way or the other.
Gary Casey
Previous post:
subj: Installing Grease Zerks For Front Wheel Bearings
Paul,
I agree with the math, however, I asked a question that no one could answer
when Stan gave a presentation on the conversion at Patterson.
The distance between the upper and lower ball joint mounting points in the
knuckles goes from 9 inches to 11 inches. The angle at which the upper
control arm rides is higher. The angle between the upper ball joint socket
and the ball and shaft is much closer to the inside edge. Has anyone ever
jacked the suspension up as high as possible and verified that the ball and
shaft of the upper ball joint does not hit the upper ball joint socket?
A secondary question is - how does the changed angle between the upper and
lower control arms affect the coaches steering and handling. I'm looking for
a theoretical not empirical response. I realize if it wasn't acceptable
people wouldn't install it!
Regards,
Rob M.
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