Bad shimmy

[kdtjb]

67 Belvedere shimmys very bad after finish line. It's was fine but wearing front runners out quick. So I replaced worn lower control arm bushings and had it aligned. After that in the shut down at about 50 or 60 mph it shimmys bad. Levals out at 30 or so. My 1/8 mile speed is 106-107 and every thing goes good from 0- 107, just does it on the slow down. Any ideas? P.S. the tire wear is good now.

 

[Jeremiah]

Tire balance?

 

[daredevil]

Disc brakes? rotors?

 

[MoparMitch]

Ball joints, tie rods ??

 

[tallhair]

Front wheel bearings properly adjusted?

 

[Hemi Rebel]

Loose nut behind the wheel?

 

[kdtjb]

Tire balance?

I did get new front tires at the same time, so I had them rechecked. They were done fine when they were put on and balanced the first time.

- - - Updated - - -

Disc brakes? rotors?

They are Wilwood's I checked them, they are not warped.

- - - Updated - - -

Ball joints, tie rods ??

They checked out good.

- - - Updated - - -

Front wheel bearings properly adjusted?

They are also good.

- - - Updated - - -

Loose nut behind the wheel?

Tell me more, when I took the front tires of one off the 3" long wheel studs had been pushed in. In other words the lug nut screwed the stud back till it hit the hub, but the wheel seemed to be tight. Or were you referring to the driver, ha ha.

 

[Budnicks]

where is the tire wear ?? toe in or probably towed "out" too far ?? {scrubbing front tires} caster angles wrong ?? {especially under a braking load, too upright, possibly laid back too far, is what sometimes causes that} or possibly camber angles wrong ?? something in the alignment is what it sounds likes to me... if it was that balance, it would seem to me, it would do more at higher speeds too... what kind of Upper & lower control arms do you have ?? what kind of bushings did you use ?? do you have the right pins for the LCA bushings ?? {especially if it's Poly bushings}

- - - Updated - - -

if all alignments check out then it's possibly a balance issue with combined parts {just a wild as guess}, you can have a dynamic balance done with the wheels on the car... that's not usually necessary thou

 

[Dako]

67 Belvedere shimmys very bad after finish line. It's was fine but wearing front runners out quick. So I replaced worn lower control arm bushings and had it aligned. After that in the shut down at about 50 or 60 mph it shimmys bad. Levals out at 30 or so. My 1/8 mile speed is 106-107 and every thing goes good from 0- 107, just does it on the slow down. Any ideas? P.S. the tire wear is good now.

I would go back to the alignment shop with the new details. A good alignment guy will know where to look next.

 

[SUPERSTOCKRACER]

It's your rear slicks that need to be balanced. Bubble bead balance.

 

[kdtjb]

I would go back to the alignment shop with the new details. A good alignment guy will know where to look next.

He is a fellow racer and has a good reputation with racers for his alignments. He said bring it back he would look at it again. But he is 160 miles away and it's winter. I was hoping to get some ideas to look at before I made the trip.

- - - Updated - - -

It's your rear slicks that need to be balanced. Bubble bead balance.

I have one of those, so I will check that. The steering wheel jerks back and forth when it happens. I wondered if it might be toed out a little.

- - - Updated - - -

where is the tire wear ?? toe in or probably towed "out" too far ?? {scrubbing front tires} caster angles wrong ?? {especially under a braking load, too upright, possibly laid back too far, is what sometimes causes that} or possibly camber angles wrong ?? something in the alignment is what it sounds likes to me... if it was that balance, it would seem to me, it would do more at higher speeds too... what kind of Upper & lower control arms do you have ?? what kind of bushings did you use ?? do you have the right pins for the LCA bushings ?? {especially if it's Poly bushings}

- - - Updated - - -

if all alignments check out then it's possibly a balance issue with combined parts {just a wild as guess}, you can have a dynamic balance done with the wheels on the car... that's not usually necessary thou

The suspension is stock 67. The new LCA bushings are the stock type and the pins are the same ones we had before. When the second shop did the rebalance on the tire they changed them a tiny bit, like a 1/2 ounce. Maybe thats all it takes with that light of tires & wheels. The camber looks good, the tires stand straight up and down. The caster I can't tell by looking at it. So as you said about the toe, I was wondering if toe out might effect it that way. I will try to measure that. He did raise the front end about an inch, not sure what that might do. Thanks for your reply, gave me some things to look at.