My 72' vette has a pretty bad shimmy at 53-60 mph. I recently brought it in and had the wheels rebalanced and the front end aligned, it made no difference. Any suggestions?
It also shudders pretty hard if I hit a little pothole or rough road.

Thanks,
Dale

 

Did they inspect the entire front end when you brought it in for an alignment? Shimmy can be caused by worn ball joints, bent rim, idler arm or tie rod ends. If any of these parts are loose fitting a slight bump will cause the front end to shimmy. Front Wheel bearings can also cause a shimmy at certain speeds if they are loose fitting in the front rotors. You may not always hear them whine before they fail. Put the front end of the car on jack stands and shake the tires side to side to feel for play. Excessive play in this direction suggests front end parts. Top to bottom play means either ball joints or wheel bearings. Listen for clicking sounds as you move the tires. Also check your front end bushings on the A-Arms to look for cracking and wear.

Just a few things to look at. Also just because the wheels are in balance does not mean one of them is not out of round. Have them rotate the tires to see if the shimmy moves to the rear. When I did tires for a living the company I worked for removed the shrouds that cover the tires during the balancing so we could see how the tires spun on the rims. We could see the bent rims in action. We also would wear leather gloves and feel the tires spin on the balancer to feel for imperfections in the tire. Vibrations were worse on sports cars or expensive cars with stiff suspensions.

Most bent rims were Mercedes, BMW and Volvo drivers seems these people hit more pot holes or curbs than others did Out of round rims sometimes could be fixed with rotating the tire on the rim to match the imperfections in both the tire and rim. Severely bent rims we would use a piece of chalk on the inside of the rim and pound it a few times with a 3 pound hammer to take the bend out where we saw chalk marks. I also worked with some very talented front end alignment and brake specialists to learn what I know today.

 

 

My first guess would be bushings. Did you state your concerns where you had the alignment done? Seems like they would have found the problem while doing the work

 

Just a few things to look at. Also just because the wheels are in balance does not mean one of them is not out of round. Have them rotate the tires to see if the shimmy moves to the rear. When I did tires for a living the company I worked for removed the shrouds that cover the tires during the balancing so we could see how the tires spun on the rims. We could see the bent rims in action. We also would wear leather gloves and feel the tires spin on the balancer to feel for imperfections in the tire. Vibrations were worse on sports cars or expensive cars with stiff suspensions.

This is good advice. Sometimes you get a bad wheel/tire combination that "seems" to balance, usually with a lot of weight.

 

We had our tires rotated a few days ago. she still shimmys between 55 and 65.Mechanics which did safety inspection took extra time to look over the whole front end. they said everything looked good. Tires have low mileage on them. We will check for bent rims now.

 

Dale - I've got the same problem with my '68, in the same speed range. I've tried / checked everything, except new tires. If you can borrow a set of wheels/tires, you could either eliminate that as the problem, or isolate the problem. That's my next move. I just need to find a set to borrow.

 

Tires and wheels are a small part of it and if your running Bias Ply Redlines they make a Radial Red line tire these days. Out of round tires will cause a vibration but rarely a harsh shimmy in the steering wheel. When the car is sitting for long periods of time you can pump the tires to 40 PSI to prevent flat spots but that is a vibration not a shimmy.

I would take it to another shop and have them inspect the front and rear end and also have them inspect the bushings on the upper and lower A-Arms than also on the rear suspension. When you have a shimmy and a vibration it could also mean loose parts. How is the steering? Pretty Tight or can you feel play? Try to move the wheels without the engine running and see if there is play in the steering. How many miles on the car? How many miles ago was the Control Arm, the Ball Joints and Tie Rods replaced last? All this can cause a shimmy and vibration at certain speeds. There are so many things to look at on the suspension. Heck you could even have a blown out bushing where it has dry rotted to the point rubber is missing on the one of the shocks or any suspension component it will do this to you. Any one of the bushings in the suspension that is almost shot or completely blown out then rubbing metal to metal or almost rubbing metal to metal will cause a shimmy at a certain speed.

If You know what your looking for on the suspension that is a bonus and you can put the car up on jack stands pull all the tires and take a look for yourself.

I had a weird suspension problem and did not need to ask the question out here because I knew one of my shocks were bad. If I hit a bump on a corner the rear of my car felt weird and would bounce on one side. I knew I had a bad rear shock just did not know which one until I replaced all 4 this weekend. My left rear Gas Shock had blown the gas out of it. I also have a almost completely blown upper control arm bushing on the passenger side that will clunk a little. If you seen my post where I was asking a few questions on which bushings to use with a set of 550 Pound Gymkhana springs I know to use rubber bushings instead of Poly Urethane since the Springs are going to harden my suspension and Poly will make it too hard.

I am brave enough to take on the rebuilding of all the bushings in my suspension myself because most are so dry rotted they need new ones and have almost all the tools I need to do it. My winter project this year is to replace every rubber bushing in my suspension. I hate to pay someone to perform work and I am confident in doing all the work myself over the winter months. My car is parked 6 months out of the year so I have lots of time to get it ready for Club Car shows next year.

 

Check it out, the OPs last post was March 29, 2014. It looks like he went away without checking back.

Pete

 

Pete....................the good news is.......Us/we rookies can get lots of good advice from this thread......I completely rebuilt the suspension on my project and will use these tips if I have any problems.

 

We'll DG, there is that....... & It's all good.

It just seems strange to me the way folks come on here, ask a question and then disappear.


Pete

 

True.

I try to post my results.......even on the 3rd try....It's just the right thing to do... but a few people just want a fast answer.....LOL!

Sooner or later....usually later.....I stumble on the answer in a Forum thread and gladly post a solved problem (even if I created the problem !)

 

Yea I hate when that happens someone sees a post from months ago and replies. Like me but I have added a bunch of other information that will help others

 

Like I said in post #11, it's all good. I just wonder about the OP, what happened to him? Why didn't he come back and acknowledge the replies and/or tell us what the final fix was. Common courtesy would be a thank you and resolution post. Just my opinion.

Pete

 

True! And I'm going to use that info!



Exactly!
Thanks to all you guys who have bailed me out on my basket-case project!
But don't get too comfy....I'll need a lot more bailing

 

Yup when I ask a question I always thank others and tend to let them know the resolution to the problem. I rarely ask but when I do I want them to know they helped me with the opinion or experience they have

 

My 69 had a shimmy in the 50 to 60mph range that baffled me for much longer than it should have. I checked all the things in this thread - ball joints, tie rods, wheel/tire balance, etc, including 'all' the bushings. I felt foolish (that it took me so long) when I found the problem - I had failed to check the bushings at the frame mount for the power steering piston/rod and they were shot, allowing for some movement there. What a difference replacing those (very easy job) made in the drive of the car.

 

Even more good info,,,thanks!