Part 17 – Front Suspension

The front suspension of my car had some interesting modifications done to it by the previous owner. The story I got from him was that this was all done, at least in part, to eliminate a bump steer problem that the car had. The first thing that I noticed (and thought looked very unsafe) was a 2 3/4” spacer that was added to the bottom of the spindle. The following picture shows the changes from original that were made and what I had to work with when I got the car. The lower control arm was modified by removing the ball joint and installing a Heim joint with that scary spacer and ¾” bolt. The upper control arm remained the same but was repositioned 3” higher on the frame onto an extension of the original mounting plate. The steering tie rod end was changed to a Heim joint and attached from below to the spindle rather than on top.

http://www.uniquecobra.com/gallery/f...suspension.JPG

My first thought was to return everything to original but hesitated on that for a couple of reasons. The first reason being that I have heard and/or read that other owners have also had bump steer issues with their cars. Mine was originally manufactured in late 1992 and, from what I gather, one of the first with the newer suspension, which perhaps did not have all the “bugs” worked out at that time. Bump steer in the later cars was either eliminated or not the problem that some make it out to be. Whatever the case, mine is what it is. My second reason was purely economics, replacing the Heim joint with a ball joint meant new lower control arms (or precise modifications of the ones I had) and spindles because the tapered seat had been drilled out for the ¾” bolt that was installed. I decided to clean up what I had, assemble it, and see how the bump steer issue ended up.

This next picture shows the cleaned up front end with a bar replacing the spring to approximate the proper ride height of the car. I set the caster, camber, and toe, and checked for bump-steer. My first results were not good but by simply adding a washer between the tie rod end and spindle I had, believe it or not, 0 bump steer. This might be the first modification done by the original owner that I don’t have to undo, it does, however, need some improvement.

http://www.uniquecobra.com/gallery/f...uspension2.JPG

The improvement has to do with that 2 ¾” spacer on the spindle. It just looked to me like something that could put enough leverage at the connection point to the spindle to break it. For my peace of mind here’s what I did.

I changed to longer bolts on the brake caliper bracket on the front and rear of the spindle so that I could attach a reinforcement for the spacer.

http://www.uniquecobra.com/gallery/f...spacermod1.JPG

I fabricated the appropriate pieces and welded everything together. Here are the results.

http://www.uniquecobra.com/gallery/f...spacermod2.JPG

I plan to add dust shields to the Heim joints to keep them clean and still have to install the sway bar.

To be continued…

"The first reason being that I have heard and/or read that other owners have also had bump steer issues with their cars."

Funny I know of one owner who claimed he had bump steer problems, which is documented on the Forum, but owner's....I have to question that.

It is somewhat amazing that when the car ordered by Bill Elliot and family was delivered and they checked everything out on the front end, steering, suspension, shocks, ect. they (being more qualified than anyone on this forum) found no bump steer problems.

I guess to each his own.....

For Dummies like me:

BUMP STEER


Definition: The tendency of a vehicle to suddenly veer or swerve to one side when hitting a bump or dip in the road. The condition is caused by uneven toe changes that occur as a result of the steering linkage or rack not being parallel with the road surface. This causes the wheels to change toe unevenly as the suspension undergoes jounce and rebound.


Ralph

Quote:

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Originally Posted by eliminator

"The first reason being that I have heard and/or read that other owners have also had bump steer issues with their cars."

Funny I know of one owner who claimed he had bump steer problems, which is documented on the Forum, but owner's....I have to question that.

It is somewhat amazing that when the car ordered by Bill Elliot and family was delivered and they checked everything out on the front end, steering, suspension, shocks, ect. they (being more qualified than anyone on this forum) found no bump steer problems.

I guess to each his own.....

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Rick, as I said in the post "Bump steer in the later cars was either eliminated or not the problem that some make it out to be". I know about the one you mentioned and a second one would be the previous owner of my car, I met a former Unique owner from Folsom, CA, and one in Reno, NV that talked about the same issues. Thats 4 and that might be all of them. Whatever the case my car was altered because of that and I had to deal with it one way or another. It seems to be correct now and I'm happy with that.[thumb]

The only bump steer correction that I am familiar with is similar to the attached image. It is a common correction for a vintage Mustang. The correction is not made by altering the spindle height or suspension geometry but is accomplished by relocating the tie rod attachment point. I agree with Eliminator that Uniques basic front geometry seems to be very good. All it requires is an decent alignment specialist to put it in spec.

-Geary

Attached image not attaching ???

-Geary

Rod,

My first concern was regarding the spacer. You have a Heim joint at one end, and a ball joint at the other end. Each of those joints allows for movement in two axes: longitudinal (front-rear) & lateral (side to side). However, you have now constrained the ball joint with your added brace. That was good, as I feel the car would have been utterly uncontrollable otherwise. The spacer would have basically been a noodle, free to move horizontally in any direction at both ends.

Now, however, there are three issues:

1) The Heim joint, by virtue of being the unconstrained point, will functionally become the ball joint. No matter how much grease you pack around it, you aren't going to get much into the space between the bearing surfaces like you would with an internally channelled ball joint with Zerk. Life will be short, and wear will likely quickly result in loss of alignment and handling.

2) By lengthening the lower spindle mount, you are now generating a substantial moment/leverage load on the basically stock lower control arm ball joint socket. This will likely lead to bending back & forth, even if it's at an imperceptible scale. Bending back & forth cold works and makes the metal brittle. Lower control arm failure could result. Any twisting or bending will at the very least result in erratic handling.

3) By adding the gussets going back to the caliper backing plate, you are transferring suspension loads into the caliper mounting plate that it really was never meant to take. And, those aren't the biggest bolts in the world. Should one of them fail, you will be quite instantly back to the unconstrained noodle situation I originally mentioned.

Even though Agressor's images won't post, I agree with him. I've never seen anything like this - the tie rod end attachment points are always relocated or shimmed to correct bump steer. The issue is there being a severe enough angle between the tie rod and the spindle that suspension compression or extension effectively lengthens or shortens the tie rod. Correcting that angle (a perfectly horizontal tie rod is often judged as the ideal) by moving the rod attachment to the spindle is what I've always seen. Lifted 4x4's often move the tie rod connection from the bottom of the spindle to the top of the spindle to accomplish this, for instance.

I'm not trying to rain on your party here, but I just honestly don't have a good feeling in my gut about the safety of this arrangement. Believe me, your wife, kids, friends, dog, etc. won't care how much money you saved if it winds up causing an injury or worse. When building the Chevelle, I gave up a 400 hp engine for a 250 hp one, just so I had the money to put disk brakes on for safety. I'd play this safe, reverting either to the original setup, or purchasing a new front suspension from Unique.

Zach, Thanks for the input and concern, the photos may not be showing you all that you need to see. The spacer has no ball joint at the connection to the spindle; it was attached to the spindle with a ¾” bolt that goes through the Heim joint, the spacer, and the former lower ball joint hole. I agree with point # 1, and if this were a daily driver I would probably not use this set up, it’s an area I will keep an eye on. I’m not sure I follow you on point #2, the lower control arm had been modified to accept the Heim joint in place of the ball joint that was original to the car , I don’t see how the lengthened lower mount has any more leverage on that connection than before, as the Heim joint allows for free movement. On point #3 a better picture would have helped, the gussets actually attach to the lower part of the spindle by use of longer bolts that also attach the backing plates to the spindle, the “unconstrained noodle situation” that you referred to was never present, but increased loads on the former spindle/lower ball joint connection were, the gussets I added will transfer that load to the rest of the spindle. I too was very skeptical about the way this had been modified and thought that the way the spacer was attached was an accident waiting to happen, I feel good about the current set up and believe it to be safe, but am still open to any other comments.

Heres another view

Not an automotive nor structural engineer but I question the strength of the Heim joint in lieu of a ball joint....is it strong enough to sustain the sheer forces applied by the wheel and weight of the car at speed and in a hard turning situation....would be talking to an engineer at the Heim joint factory to determine the sustainable and peak load for the device???? Also, why not make the spacer larger in diameter....1.75"-2" and use a 1" bolt????? the automotive guys I always talk to say use at least twice as big as you think it should be!!!!! Better safe, than having a wheel become dislodged at speed in a tight turn??????

Just remember, when they ask you....you gotta say "I built it"???????