front suspension shimmy

[Barnacle Bill]

I started to get a slight shimmy from the front end of my 94 convertible and decided to do a urethane bushing up grade and rebuild the front suspension. Replaced upper/lower ball joints, tie rod ends, replaced bushings in lower A-arms, steering rack and sway bar. Just picked car up from the alignement shop and discovered the shimmy problem is worse. Any bumps or un-smooth roads seems to trigger the problem. Car has FX3 suspension. Any ideas on how to correct this problem.

 

[dougelam]

Bent wheel?

Sent from my SM-T530NU using Tapatalk

 

[DonB]

If the front end is correct,..I'd check tire run-out/balance and/or wheel bearings. Get the front off the ground and manually spin the tires. Does the tire tread track true? Bearings noisy? While driving,..Does the shimmy decrease or increase when applying brakes? Or is it there all the time? Does the car drive straight?

 

[Hib Halverson]

Problems like you have are very difficult to diagnose via the Internet.

A "shimmy" can be caused by a wide variety of problems..

Worn or defective suspension parts
Defective or worn tires.
Defective wheels.
Incorrect front end alignment
Worn or defective steering components
faulty or worn suspension dampers
Loose parts in the car's structure
Collision damage to improper repair of collision damage

And that's over and above the normal steering column and body shake typical of C4 convertibles which have awful structure to begin with.

My suggestion is to find a really good suspension service shop and have them evaluate the car.

Once you have the shimmy fixed, my guess is you will learn to hate all that urethane stuff you just installed. Uregthane bushings, stabilizer bar mounts, rack mounts and so forth are great for track cars and cars which are really driven hard on the street, but, since it is pointless to try and make a track car out of a C4 convertible or even drive it really hard on the street, urethane bushings and stab. bar mounts make little sense. What they will do is noticeably increase suspension noise and harshness, and, if the harshness doesn't irritate you, if your car gets driven on cold/damp weather, the squeaking will.

 

[Tom Bryant]

How are the tires? When were they last balanced? You could have a broken belt in a tire also.

Tom

 

[kpic]

My suggestion is to find a really good suspension service shop and have them evaluate the car.

Excellent advice.

 

[Barnacle Bill]

Problems like you have are very difficult to diagnose via the Internet.

A "shimmy" can be caused by a wide variety of problems..

Worn or defective suspension parts
Defective or worn tires.
Defective wheels.
Incorrect front end alignment
Worn or defective steering components
faulty or worn suspension dampers
Loose parts in the car's structure
Collision damage to improper repair of collision damage

And that's over and above the normal steering column and body shake typical of C4 convertibles which have awful structure to begin with.

My suggestion is to find a really good suspension service shop and have them evaluate the car.

Once you have the shimmy fixed, my guess is you will learn to hate all that urethane stuff you just installed. Uregthane bushings, stabilizer bar mounts, rack mounts and so forth are great for track cars and cars which are really driven hard on the street, but, since it is pointless to try and make a track car out of a C4 convertible or even drive it really hard on the street, urethane bushings and stab. bar mounts make little sense. What they will do is noticeably increase suspension noise and harshness, and, if the harshness doesn't irritate you, if your car gets driven on cold/damp weather, the squeaking will.

Thanks for your input Hib, car has 38000 miles, accident free, tires are 2 years old with 4000 miles. car is solid when driving on normal streets and highways, no rattles, squeeks or shimmy. brakes are are great and have no effect regarding shimmy. I replaced rear FX-3 shocks last year and will replace fronts when they get here this week. I will be taking car to a highly regarded suspension shop who previously identified, explained and showed me all of my suspension problems after local shop said all was good. I will also have them check balance on all 4 wheels. My confusion stems from what you called "normal steering column and body shake". this is my first corvette and only corvette I have ridden in. My goal was to see what a C-4 with new suspension handled like.

 

[Barnacle Bill]

Shimmy solution

While waiting for shocks, I had disconnected the front sway bar to do a more accurate bounce/rebound test and found drivers side was very soft/loose. This raised my hopes that the new shocks would be the cure. New shocks have arrived and are installed. Cured 95% of shimmy problem! While checking the new shocks out before installation, I noticed that it required a lot of force to rotate the shaft end gear with my fingers (Compared against 6 other new and used FX3 shocks). I drove it three times in 4 days for a total of 60 miles when the SRC trouble light blinked on. I removed the front actuators and both had broken plastic gears. The quest continues. New actuators around $1000. Rebuilt actuators with aluminum gears under $300 (C.C.) Can anybody speak of their experience with this choice? Will the aluminum geared actuators handle the problem? Is there a way to measure or check how much force is required to turn the gear? What would be the range of the correct force measure?