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TCP R&P Shimmy Issue

C

Chris Kennedy

Member
Hi:

I am using a TCP manual rack & pinion on my '65 289, and get an occasional steering wheel "shimmy" back and forth between 60-70 mph, mostly when I turn the wheel a bit to the right (like when changing lanes). I have checked and re-checked all the usual wheel/tire balance, tie rod issues etc., and am running almost four degress positive caster (the tires are 225 60 15 on Torque Thrust Ds), and the shimmy is getting a lot less, but am wondering if anyone else has had a similar problem. On another forum, someone had an identical problem and said that the problem went away with a bumpsteer kit---yet steering wheel shimmy isn't a classic bumpsteer symptom (at least I don't think it is). Otherwise, the car's great! Any thoughts?

Thanks!
/s/ Chris Kenendy
 
You may want to check the play in the unit. You will have to disconnect the tie rod ends. I would do it one at a time and push back and forth slowly to see if there is some play that there should not be.

Otherwise if everything is tight and aligned correctly, you may very well have a bump steer issue. 65s are notorious for that.

Mel
 
Thanks---it's weird about the "bumpsteer" idea. The car doesn't dart or steer as you go over bumps and the suspension moves up and down causing the toe to change, which is what I have thought of as bumpsteer. Still, I will check further.

Thanks,
/s/ Chris
 
You stated you are running 4 degrees of caster but no camber or toe measurements.

With that mach caster cranked in you should have great tracking and steering wheel return.

Tires static balanced or dynamic?
 
Yes, the wheel does center very well. The wheels/tires were balanced using the Hunter "Road Force" system (twice)---I think that means "dynamically" balanced. I am running flat to maybe slight positive camber, but can't recall toe. It took some effort to get the 4 degrees positive (I think it is closer to 3.5 to 3.75). At some point I would like to get slight negative camber, but I am holding on that for now until I get a handle on the shimmy. The shimmy does seem to be getting much less, still it's weird. I am asking TCP about it again as well, and mentioning the bumpsteer issue.

Thanks!
/s/ Chris
 
"Chris Kennedy" said:
Yes, the wheel does center very well. The wheels/tires were balanced using the Hunter "Road Force" system (twice)---I think that means "dynamically" balanced. I am running flat to maybe slight positive camber, but can't recall toe. It took some effort to get the 4 degrees positive (I think it is closer to 3.5 to 3.75). At some point I would like to get slight negative camber, but I am holding on that for now until I get a handle on the shimmy. The shimmy does seem to be getting much less, still it's weird. I am asking TCP about it again as well, and mentioning the bumpsteer issue.

Thanks!
/s/ Chris
Click to expand...

Been using a GSP9700 for years. It's only as smart as the operator. It will allow you to static balance wheels. I don't think road force variation is your problem, at least not from your description.

Check your rotors as suggested and update your post.

Any chance you have an alignment printout? With that much caster I'd run a bit negative camber and positive toe.
 
Thanks! I think I do have a printout and will find it and report, and I intend to check the rotors early next week. I will let you know what I find out.

Regards,

/s/ Chris
 
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