Late CSL race suspension, steering rack?

[Bavman]

Wondering about the geometry on the front suspension. I am trying to add a rack on a track car. Did the later race cars run a rack? Was the front lower arm location moved? I have read that the Group 5 e21 ran the same front as the last CS race cars, the e21 has a rack.

I have a Maserati Biturbo, it has CS front struts, that is the rack and steering arms I am going to use. I also have some knuckle risers that allow use of e28 strut tubes, they may factor in also. Looking at early e23 arms as I think I heard some of the 7 series parts were used on the Grp 5 cars.

Anyone have any experience with this? Any photos of front suspensions? It would make fitting the rack easier if the front arm was mounted forward like the e21/23/Maserati.

Thanks

Al Taylor

 

[ElGrecko]

You will need to make sure you don't end up with a bunch of bump steer when you're mixing and matching parts like this. If you are using the original Maserati rack and lower control arm mounting points that's a good start as those parts are designed to work together. You will need to look at the rack width and the length of the tie rods and length of your lower control arms and where the rack is relative to the lower control arms and work out the geometry. Also look at the planform geometry and figure your Ackerman (or anti-Ackerman if you prefer). It's highly unlikely that mixing parts from different cars like this is going to provide good geometry without some changes to rack location, lower control arm length tie rod length or both (most likely) to get it all to work together. Just because you can bolt it all together doesn't mean it will work.

Assuming that you've lowered the car a good bit, unless you relocate the lower control arm mounting points it's difficult to get the roll center in the right place. I'm assuming that by the term "knuckle risers" you are using a block type spacer to lower the outside ball joint location and get the roll center back up to where it needs to be.

It would be easiest to get a suspension geometry program that you can put in the location of the joints and it will spit out your geometry and work out camber gain vs roll angle as well as bump steer and Ackerman angles vs steering angle. I have found that even small changes in front end geometry can have big changes in grip and handling on the track and it pays to do your homework to get it right. The cost of one of these programs is small compared to what it will cost to modify hardware and it's a lot easier and cheaper to get it right from the start.

 

[Bavman]

Yes, asking in hopes of copying someone’s proven set up…I really need a close look at one of the e21 grp 5 cars…

Thanks

Al