SLC Bump Steer Spacers

Rich Kruger

Supporter
I recently aligned my car including successfully setting the frt bump steer. Using a 1 inch steel spacer as I have read in some posts got me within .05 of a degree in the frt. The rear is a different story. My car does have the the double shear set up. The car came with a longer lower spacer and a shorter upper spacer. The angle at ride height was way off from the rear lower control arm. I want to at least get it close in order to drive the car to a racecar alignment shop. I swapped the spacers and it was closer but still over a degree off. What type of spacer lengths has anyone used in the rear? Thanks
 

Howard Jones

Supporter
The way I did mine was, put the car on its tires at correct ride height, Then remove one rear spring and put the whole thing back together without it, set that corner on a stack of 4X4 and assorted shims under the chassis so that it is at same ride height as other side.

Now the car is sitting at correct ride height but the test corner is free to move up and down. Put floor jack under tire, c-clamp straight edge to two jack stands so that the straight edge is parallel to the center line of the car. Then position so that it is very close to the tire at the center line.

What you have now is a tire that is either farther away from the straight edge either at the front or at the rear (toed out). Put a stack of washer on the bolt that holds the toe to the link. Adjust link length so that the tire distance to the straight edge is equal at front and back.

Now you can add or subtract washers to achieve no toe change as the tire is jacked up and down. Once you have that, measure washers for your spacer length. Add one or two turns on the toe link to put a minimum put toe in adjustment on the car. Good to go.
 

Rich Kruger

Supporter
Thanks Howard. I will check it this way. My question is about what size upper and lower spacers did you end up with. I am puzzled at the way the car was shipped with seemingly custom made spacers that when the rear tie rod was compared to the lower control arm angle was way off. Does the about equal angle hold true at the rear as it did at the front? I know each car is slightly different but approx what were you spacer lengths? Thanks in advance
 

Howard Jones

Supporter
I believe the cars are shipped simplify assembled so as to deliver the parts. IMHO the entire car should be assumed to need a piece by piece dissemble, clean, check out and reassembly.

My car uses the original uprights and did not have a double mount (upper and lower) toe rod arraignment . I made my own pieces for this when I upgraded the brakes so any measurements I might forward to you would do you no service. However the method I used to address rear bump steer will work even if it is a bit caveman.

The general rule of the arms being flat and the toe rod being parallel to them is true but the actual in situ toe change measurement is what is important. Only testing and measurement will net you a actual spacer length. Start with a stack of washers that will give you a flat arraignment as in the general rule. Then measure what you have and go from there.

What you are after is NO! NONE! toe out at any position of the real in service rear suspension travel. Then from there a minimum toe in at ride height. I was able to set my rear toe in to 1/16" per side and get no toe out through out the full travel of the rear suspension. Be sure to reinstall the shock as I may not have been clear in post #2. That's about as good as is necessary.

Take you time and enjoy the process. You can aline the entire car with a straight edge, steel rule, bubble level and some string. It takes time but it will really give you some insight into how the suspension works. The SLC can be setup to be near perfect on bump steer and especially camber gain at both ends of the car and the chassis (at least mine) was a square as I could measure. Something less than 1/16 ' in all respects completely square.

Start with a measurement of the chassis and mark the centerline on the chassis near the bottom of the car where it will always be accessible from Then it is all just some straight forward measurements and a bit of trig.
 

Neil

Supporter
Amen on that Howard. In the '70s I was building a Sablel Mark III (a lightweight mid-engine sports racer) in a rented shop but I decided to bring it home to finish it in my garage. The car was a roller so I tied a long tow rope to it and had my wife tow me home while I sat in the car. The car was all over the road, darting left and right. I found later that my "eyeball" setting of the suspension was way off- I had 2'' of toe out! I should have actually measured it but it "looked" straight. That was a good lesson about toe-out.
 

Howard Jones

Supporter
Rich, I will PM you with my Ph#. I'm in Central time zone so if you get to a point that you want to talk give me a call. Good luck. Work slow and take a mental break every couple of hours.
 

Rich Kruger

Supporter
Thanks Howard. I already have a string set up and a straight edge for under the car to square the set up. I purchased a digital angle meter that is very helpful. I was able to at least get the basic alignment close. I’ll spend this weekend fine tuning it. (At least when I’m not watching the 24hrs of Daytona). I’ll call if I have any questions. Thanks again
 
Top