Re: [AMC-list] suspension 101

[Frank Swygert <farna@xxxxxxx>]

I think you're right, positive castor helps stability at least for normal street driving -- might not for hard driving. On second thought, I think the strut rod suspension was just a way to make the front suspension cheaper to build and lighter without introducing too much negative handling effects. The best riding/handling suspension is unequal length A-arms, but they are generally heavier due to the weight of the arms than strut rod suspensions. Even unequal length A-arms introduce some negative castor after a certain point. This is actually one advantage to the old lower trunnion joint suspension -- it was very light weight while having the mire ideal unequal length arms. Most manufacturers that used a lower arm had a heavy stamping, but the only ones I can think of right now also mounted the spring on the lower arm, so the lower arm had to contend with that pressure also. 

The early Mustang/Falcon, however, was a screw-up on Ford's part! Some engineer didn't do all his homework. For 66 the problem was corrected. For 64-65 Mustangs and pre 66 Falcons just relocate the pivot holes for the upper control arms down about an inch -- the famous "Shelby drop", named after Carol Shelby who was the first to do it. The 62-up AMC strut rod suspension is very similar to the Ford, at least for the lower arm. AMCs don't push the bottoms of the wheels out when the weight is off, never have! 

--------------
Date: Thu, 28 Jan 2010 21:19:54 -0600
From: "Armand Eshleman" <aje1@xxxxxxxxxxxxxxx>

I was day dreaming today and got to pondering about the front end suspension
geometry on Javelins, and most other AMC cars for that matter that are
similar. My thought was that when the wheel moves up and down that the
steering geometry changes because of the strut rod. When the suspension
moves up (spring compresses) or down (spring expands) the wheel is actually
moved a small amount toward the rear of the car thus creating additional
positive castor. This must have been a favorable effect.

Positve castor usually creates additional stabilty, correct?

Even when turning corners?

Is this why Mustangs with the strut rod in front of the wheel handled like
crap? (castor went negative with suspension travel)

Was this possibly one of Donohue's "Unfair Advantages" ????

What do you guys think??

--
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)

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