Thread: front end shimmy

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Just looking for some suggestions on what to do about front end shimmy in my 24 t bucket. I recently went from bias tires to radials and am now getting some front end shimmy at times. I had no troubles with the bias tires. I messed with the air pressure but can see no change. The front end is out of a 46 ford with 38 ford spindles and chevelle rotors. All of the components are new. I hear that alignment could be a remedy , but wanted to check if anyone knew of any other possible causes. Thanks for your help.

if it drove ok with the bias then it should drive better with the radials. sounds like some body messed up on the bal. id recheck the bal.

If, after re-checking the balance like Mike said, you still have a problem, you might try dialing a little more positive caster into the axle.

i might be wrong but i took that to mean he had a front end shimmy going down the road at 50 mph going stright, after he changed tires and if that is correct i still stand behind the bal. if he is running a race course then maybe some of this other stuff. caster might make it steer funny or duck all over the place, but i dont think it will make it shimmy, but ive been wrong before.

when i think of a shopping cart i would think it did what they do because it had 0 everything. how about a drag car o camber and a lot of caster, to make it go stright, not keep it from shimming.

and why are you up so late?

Thanks for the replies. I've tried the rebalancing already with no results. I might want to describe the shimmy as wheelslapping where both wheels shake back and forth in unison. Tapping the brakes or turning will usually stop it. This happens at low speeds only so far and usually when I hit a bump in the road. I've never seen this before except on a shopping cart like you guys have mentioned , and I don't want it to tear up my front end.

Sounds like the "death wobble" many solid axle vehicles get at certain speeds and road conditions. It could be caused by incompatible front and rear tires, some sizes and brands just don't work together on some cars. Radials front/bias rear will do it more, but mixed brands can do it, too. Seems funny to change rear tires for a front shimmy, but it might do the trick.

You may have something loose in the front end.

Especially the king pins.
Check to see if there's slop there.
Check as well to see if the kingpin bolts are tight.

Tap the kingpin lock bolts in with a hammer blow.
Cushion the blow by using a soft drift - brass, copper, aluminum etc.
Then tighten the kingpin lock/steering stop nuts to the correct torque.
If you simply tighten the nuts the kingpin locks won't be in as tight as they should be.

DennyW makes some good points about caster.
Especially in a T-Bucket with it's large disparity in size between bigs and littles.

Get the car front end up on jackstands when you check for steering component looseness and while you're there, spin the wheels by hand and see if you have an out of round or bent wheel as well as an out of round tire.
Out of round radials are uncommon, but it does happen.
Out of round is more of a problem with bias-plies.

Were the tires balanced on a dynamic balancer?
If done on a bubble balancer they will be in static balance, but possibly not in dynamic balance.
In other words, you could have a side to side unbalance and not realize it if you used a bubble balancer.

And like techinspector1 says, dial in a little more caster if everything else looks good.
Get yourself a swinging protractor from Sears or other and see how much caster you have.
Measure caster on a level floor.

6 degrees positive is a good figure to shoot for on most hot rods.
(Positive meaning the top of the kingpins lean back.)

sounds like something is wore out or to much play in the steering box. adding caster might help, but its not a fix, its just putting so much weight on the fromt end it cant do nothing but go stright.

Thanks for the replies, I'm going to get the car up off of the ground and check if anything is loose, everything is brand new up there , but I'll give it the once over. I had absolutely no shimmy with the bias tires and that is what has me puzzled. I put hoosier's pro-street 31-16.5-15's in the rear and kuhmo 165-80-15's up front (the smallest 15's I could find) . They were all spin balanced and rechecked. The caster according to the guy who set the frontend up is at 8 degrees positive. I'm wondering about toe in / out though.