Re: [AMC-list] suspension 101

["Armand Eshleman" <aje1@xxxxxxxxxxxxxxx>]

Tom and Frank,

Thanks for the responses, I'm still trying to figure out what Donohues
"Unfair Advantage" was with the Javelins in Trans Am racing. I know they
used Porsche brakes in front, but I haven't been able to determine what
other ideas they came up with. I'd love to see a 70 Penske/Donohue Javelin
for real to check it over.
Armand
----- Original Message ----- 
From: "Frank Swygert" <farna@xxxxxxx>
To: <amc-list@xxxxxxxxxxxx>
Sent: Friday, January 29, 2010 4:12 PM
Subject: Re: [AMC-list] suspension 101


> 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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