off topic suspension fabrication question

[geoff]

We are building the worst idea ever used in a drag race -- a FWD drag car. Last year the car went 8.8 @ 167 and now we are building a new chassis to the SFI 25.5 Spec.

The question we are contending with currently is how to setup the rear suspension. We are using a 4 link system, traditional setup with parallel lowers and V uppers. The car will have wheelie bars to squat on, however the question i have been losing sleep over, is what can the rear suspension do in a FWD application?

Where should the IC be placed and why? I have my own opinions and would love to hear others...

for some pics of the car check out





thanks

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[025]

Definetly not my field, but the only thing that I can think of is to run it a little on the stiff side. Reason I say this is that if the back trys to roll to one side or the other from the engine torqueing over it would cause the opposite side front tire to lose its already limited weight and break loose. Is any one runnning a sway bar on the rear? Other wise I dont think that antisquat is going to apply since the rear would have to be pushing in order to make much effect. I would think the pivots effects would be minimal. Wonder what the effect would be of trying to put as much weight as possible in front of the front tires, only thing I can think of is a speed wobbling rear but possible a better launch. Matt

[geoff]

well the motor is not mounted traditionally like a rwd motor, it is mounted left to right so it just would rock front to back. however, we are running solid steel motor mounts so i dont think it should move anywhere

in terms of the antisquat issue, the car will sit on a staging break at the line and release the brake as it launches obviously. the staging brake is attached to the rear wheels so the only moment that is placed on the rear axle is from the staging brake. otherwise the rear wheels are only there for a

in terms of weight transfer, the car has a set of wheelie bars in the back so that under hard acceleration it sits on the bars and there is a large torque arm placed on the front suspension from the bars. because of these we sprung the rear susp as lightly as was possible, so that as soon as the car squats it lands on the bars.... thanks for your input!

[Brian Mapes]

geoff, post some pics of you toyotat with the centermounted arms. thanks.

[geoff]

if you got an hour go through all the directories here

www.full-race.com/422

if you need more recent pics i can take some. all the pics on there are pretty old

[Brian Mapes]

link doesnt work

[geoff]

sorry wrong link

http://www.full-race.com/490/

[ntsqd]

Ideally you want the geometry to resist compression from weight shift during the launch. Probably the best way to approach that is to think in terms of Anti-Dive for the front suspension of a RWD vehicle.