90 Scottsdale long bed "shimmy"

[Vicb]

I have a 90 Scottsdale with 53K. Just replaced Uniroyal Laredo's with Douglas P23575R15's. I have a shimmy between 43-52mph that comes and goes. Some days its there, some its not. Checked air pressure, balanced the new tires twice. Used a Road Force balancer one time...they said one tire was bad. Took it back to the dealer, they rebalanced, said it was fine. Shocks don't give the bad mushy bounce when I jump on the bumper, but they are original. Front end has been aligned. I feel darn near every road bump as if I'm riding on tires made of wood. I could run over a pea gravel and feel it. Anybody got any ideas?

[racedvl]

I would get the front end checked out. Make sure everything is tight. Wheelbearings, ball joints, tie rod ends, ect. I take it the shake was not there before the new tires? It almost could sound like a driveshaft that needs to be balanced. I dunno, just some ideas.

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http://hometown.aol.com/racedvl/racedvl69index.html

Crystal Lake IL. 40 Miles northwest of Chicago


It's not what you buy, it's what you build!!

I did not climb to the top of the food chain, to become a vegetarian.

[Vicb]

racedvl, thanks for the reply. Unfortunately I can't tell if the problem was there before the new tires, as the old tires had cupped from mis-alignment-I had moved them to the rear, and they bounced a bit around the same speed. The shimmy does seem to be different, though, after the new tires. Ride is rougher on the new tires than it was on the old, worn ones, even with the cupping...problem seems to be a little more noticeable when accelerating uphill. Front end was thoroughly checked, aligned, and factory alignment kit (cam bolts) installed. I don't understand why the shimmy comes and goes (at the same speed). Sometimes its there at 45-50, sometimes its not. Its really got me puzzled.....the driveshaft balancing might be an idea....

[DennyB]

Vic,
If the old tires were cupped (various intermitten shallow spots around the tire) I would think shocks are the culprit.
Also check tie rod ends, Idler arm and center link.

[71GMC_3/4T]

Check the Idler Arm. If you can move the end of it up and down, it needs a new one. Scribe around it before you pull it so you can put the new one back on in the same position.
I've had this problem on two different pickups and I'm sure my GMC needs it too, but there are a lot of other front end parts it needs.

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1971 GMC 402/TH400
Workin' on it!
Gettin' on it!
Lafayette, CO
**Looking for a nice fleetside longbed for my GMC.