55 convertible shimmey

[Frustrated Bob]

I have 55 convertible with ls1 and 4l60e.Having problems with shimmey at 45 to 55.Driving me crazy. 17 inch foose wheels and Nitto 235/45/zr17 tires.Repaced steering box to a 500 box.Upper control arms Heidts 6 degee castor with QA1 stocker shocks.New ball joints and all bushings replaced.Front end aligned ,tires high speed balanced ,new rag joint and drive shaft balanced.Friends keep saying tires to big for stock suspension.Have 9inch currie rear.Any help would be appreciated.Thanks

[carls 56]

:hello: hi bob and welcome. glad you could join us. maybe you could put a different set of tires on it and see if there is a difference. :confused0006:

[mickeywestsr]

Welcome Hoss, carls has a great idea.

[Chevy Chase]

Bob, welcome to trifivedotcom. If you are experiencing a shimmey in the steering wheel after all the work that was done, I think the ball joints are suspect, even tho you had new ball joints installed. Who installed the ball joints? Did they put grease in them? The second area I would look at are the wheel bearings. Third area I'd look at is idler arm to tie rod play.:anim_25::sign0016:

[Frustrated Bob]

:hello: hi bob and welcome. glad you could join us. maybe you could put a different set of tires on it and see if there is a difference. :confused0006:

thanks but tried 2 other sets. 1 off 62 nova 17 inch 225/45/zr17 and 15 inch rally wheels that didnot shimmey. Idler arm has been replaced.ball joints were installed by friend and myself.problem was there before we changed them.repacked and tightened wheel bearings.x member had been butchered by previous owner but we have welded in plates to strengthen.now everybody understands my frustation.been chasing my tail 9 months.thanks

[rwhit57]

Did I miss something Bob? By the way welcome! But did you say the other wheels did not shimmy? If that's the case isn't the problem solved? It's one of your tires or wheels.

[Geoff]

Bob,

Sounds like a cool car. Please post some pictures of it.

[belairrudy]

I agree with Randy. Sounds like a wheel or tire causing your shimmy. But would love to see some pics of your ride.

[Frustrated Bob]

sorry guys but tires didnot shimmey on cars that i borrowed them from.same shimmey on convertible.new to website.will send pictures.thanks

[oldcarnut56]

6 degrees caster is a lot. i'd back it off to 3 degrees and take it for a drive.ever have a shopping cart with a wheel that shimmies? that the same problem too much caster. give it a shot sounds like you've done everything else already.:anim_25:

[55ChevDelray]

Generally...vibration or shimmy is caused by tires out of balance. Wandering and pulling are usally alignment issues. Those wide tires can be tough to balance, just get someone that knows what they're doing.

[57-150-wagon]

when did the car start to vibrate ?

[Frustrated Bob]

ever since i bought car.tires were high speed balanced on car.i think we will put new rotors on.believe bolt pattern might out of center.if this doesn't work it's front clip time.any recommendations on clips.thanks

[57-150-wagon]

have you checked the pinion angle on the rear end ?

[Frustrated Bob]

yes but have ruled that out.when high speed balancing tires on car had the same shimmey mechanic said my wheels/tires were out of round then tried 2 other sets of rims&tires still shimmey's.just finished driving friende 56 belair with fatmans front clip.blew my mind.what a difference.about ready to give up.ride was so sweet.thanks

[hamer36]

check the drive shaft for balance.

[Chevy Chase]

Bob, You have given us very little to go by. You have said, "Having problem with shimmy at 45 to 55," Been chasing my tail for nine months," "Believe bolt pattern might out of center." Sounds like you have only owned the car for 9 months? Has the "shimmey" been there since you took ownership? Please tell us what you are experiencing. Is there a shake in the steering wheel that is going up your arms? Is the front end vibrating at 45-55 mph making the car hard to control? Is there a wobble in the front end at 45-55 mph causing the car to vibrate? Telling us what you have replaced, and telling us what you are experiencing are two different things. Be more descriptive with the phenomenon you are experiencing, the circumstances, unusual occurances. Use more than the one word shimmey and we might be able to help diagnose the symptoms/occurances. Going solely on what you have described, I'd replace the front hubs and wheel bearings.:anim_44:

[belairrudy]

You've got yourselve a puzzling one there Bob. But you are at the right site. The guys here are full of knowledge. I am going to keep an eye on this thread!!!

[Frustrated Bob]

have owned the car for almost 2 years.spent 15 months rewiring.interior and repainting.once again new to website and still a rookie.still trying to figure out how to put pictures on site.steering wheel shakes at 45 to 55.shake is not as bad when no passenger in car.tightened up shocks and not as bad but think that is just masking problem.thanks

[fiftyfivechevy]

I had a similar problem with a Dodge Truck. I took it to get it lined up and when I got it back it shimmied like mad, but before the alignment it was okay?. What I found was a worn out idler arm. Apprarently when the alignment was way out, it must have put the idler arm in a bind and kept it from allowing the front end to shimmy? My suggestion is to have someone turn the steering wheel back and forth while you are under the car watching all of the steering linkage for any excessive movement. If everything is new like you say, you should not see any slop in the pitman arm, idler arm, ball joints, or tie rod ends. I have aligned the front end on most of my cars myself like the old timers used to do it. I would also recommend that check your caster . turn your wheels as far to the left and right and measure how much up and down the fender well moves just above the centerline of the tire, it doesn't have to be exact. On a 55 chevy, it should not move at all if it is at the recommended zero caster setting. But since you have large tires on the front, you should want a little positive caster which means the right front fender will move up when the wheel is turned to the right and move down when turned in the other direction, the left fender will do the same when the wheel is turned to the left. Caster makes the steering linkage raise the vehicle on the side that the tire turns towards, this in effect makes the car go straight since any tendency to turn to one side requires effort to raise that side of the car. Most cars steer well with about 1/4" movement up and down when the wheel is turned from one extreme to the other. Both sides should move up and down the same amount unless the alignment shop made a correction for crowned roads, which in that case, the passenger side will move slightly more than the drivers side, Excessive caster causes the tires to wear faster and also increases the effort to steer the car. Insufficient caster can cause the car to wander and in some cases may cause the car to be so unstable that it can shimmy or vibrate at a certain speed. IF your tires are really large and extra wide, you may need a little more toe-in than the 55 Chevy manual says, so that the tires are parrallel when driving down the road.
Hope this helps,
fiftyfivechevy

[clancio]

Hello and welcome.
Does it do it if you just jack up the rear of the car in your garage and drive at those speeds?
No? It's in the front end...
Yes? Pull the rear wheels, install the lug nuts back on to hold drums in place and try again.
Still there? Look at driveshaft and see if it hopping (out of balance). Look at drums, do they wobble? Bent axle?
Looks ok? Look at rear of trans and see if mount is shaking.
Hope this helps.

Edit: I know it's been said you feel it in steering wheel but I have been fooled before with a rear vibration being felt in the front.
Just thought I would help rule out anything in rear.

[Frustrated Bob]

Frustrated Bob is no longer frustrated.found previous owner had removed supports for steering collum to firewall.made new ones.drives super.i guess wheels were't bouncing as much as i thought.thanks for all the advice.pictures will be coming soon