4cefed

I get a shimmy in my front end around 65-72 mph. It does not occur at any other speed. It has done this at varying degree ever since I bought the car. Recently it has gotten worse. About 2 monthe ago I put on some new wheels and it didn't change the shimmy at all (same tires since I bought the car). That's why I am thinking it's not the wheel balance.
Could worn bushing's or ball joints cause this?
Just wanted some idea's before I take my car to Aaron Scott. That highway trip is going to wear me out if I have to deal with it all the way to Georgia.

MWR

Joel, try the tires. Something must be out of balance or loose up front (even tho they have been balanced, the tires could still be weird -- delamination or belt separation or some such, especially if they are old). If the car has a lot of miles, it could be the ball joints. Another thing to look at is the brake rotors, which could be measured for runout instead of outright replacement. Don't forget to beat around on the tie rod ends. Lots of stuff to get loose up there, depending on the mileage. Tires or rotors would be my first suspects, however.

Rgds,
Mark
'92 ZR-1 #032

P.S. Warped rotors will likely show up as some steering wheel shimmy when you slow to a stop. Bushings I would not consider an issue unless you can actually see them curling out of the suspension components.

[This message has been edited by MWR (edited 07-29-2001).]

VetBoyZR1

I had that problem on an XJS a few years ago, and it was a bad tire.

Tyler Townsley

Find a tire dealer with the latest Hunter balancer. Have him balance and check the rim for trueness (Make sure it is not bent). Do front and rear. I have seen new rims bent in shipping. If you have your old rims check them to see if one was bent. I had mine balanced 3 times before they noticed one was bent.

Tyler

89'Bowtie

I am having a shimmy problem too....here it is let me know if you can relate and we can sway ideas.

here it is........

I have a bouncing 96 Vette - really bouncing.

I have checked the front end and also had the front end checked by a
front end person all -OK. Tie rods appear to have no play. This is very
unusual because hot weather seems to be a factor in the symptoms.
Outer tie rods are fine-no play, upper and lower ball joints appear OK
with no play. Adjusted nut on shock by increasing and decreasing
pressure on shock mount - with no effect. The vehicle has has 50K miles.
I HAD ALL 4 TIRES BALANCED 3 TIMES. I am the 2nd owner, one of inner
tie rods has been replaced - driver side.

There is no bounce when the vehicle is cold in the morning. Then when
the weather heats up as soon as you go over a bump - you get the yo-yo
effect and lots of shimy in the wheel. This is not pleasant to say the
least. If you have ever driven a car with a broken or no shock - you'll
know what I mean.

I suspect a couple of things. The shocks which could be heat sensitive,
this would be a first. The rack and pinion which has acquired some play
and gets worse with heat. Some people have tossed around the leaf
spring - I do not suspect that at all - unless broken. I went over the
leaf very carefully and did not see anything or feel fractures, unless
we are talking about micro fractures- we can go on a lot of limbs here.

There could be a marginal component in the front end that is going bad
and with the temperature increase it causes the problem.


People are telling me it is the shock, do not know if this helps you or it is the same prblems, but i thought i'd give you my notes to see if it helps you. If it does there are a whole bunch of responses in the C4 Tech and Perf sections about my "Shimmy" post.

ZR1991

I eliminated it in my ZR1.. for over two years now, by checking the balance and truness, as others suggest.

I also did three other things... When the wheels/tires were spun on the balancer, I actuall held a straight edge against the machine, so I could see tread alignment. Found what looked like a bad tire, but was a bent rim.

Second, I insisted on weights outside and inside, regardless of the dispute over the cosmetics.

And third and often not thought of, I upped the tire pressure to 31-32 cold, and matched them exactly. That made a surprisingly big difference. I believe because of the width of the tire, they are sensitive to pressure distortion. When we had the first cold spell last fall, and the air obviously contracted, the car had the dreaded shimmy, which I had successfully eliminated previously. Then on a hunch, I checled the pressure, and they were down to 25. The problem was immediatly solved. So I check pressure at least every couple weeks, or when the weater drastically changes.


Hope this helps, mine is smooth as glass.




[Modified by ZR1991, 9:36 PM 8/9/2001]

4cefed

Put new tires on the front today and the shimmy is gone. I guess the old tires were bad even though there was plenty of tread left. They were rock hard.

89'Bowtie

What kind of tire did you have that was causing the problem?

4cefed

I had some Comp TA's. I went with the Dunlop sport 8000's. I wanted the BF Goodrich KD's but at $1150 per set I passed.