Torsion Bar frontend "shimmy" on brogie roadster

[555brogie]

Could anyone lend me a hand in trying to eliminate a side to side "shimmy" in my brogie roadster with a torsion bar frontend/axle???

I run 1/4" toe in and have .001" clearance on all bushings to kingpins. More toe in slows it down.

I have 10 1/2 degrees of caster which all the chassis guys say is fine.

The shimmy starts on the top end and gets worse at a certain MPH zone (guessing around 50 mph down to 20mph) when stopping. It does shimmy while accelerating but I don't feel it at the wheel, however I can see it through the air holes in the fenders.

I installed a temporary funny car style "steering dampner" which slowed it down but didn't eliminate it.

I have a little bit of slack in the steering box which I believe may now be the culprit. No slop in any of the rod ends.

Any help would be greatly appreciated!!!!!!!

[Freddie]

the only time I had any tire shake or anything in my Altered was when the front tires were a little low on air..

You wount feel it going down track on a properly set up car.. you should have most of the wieght on the rear wheels under power.. when you get off of it is when your front end comes into play.. I would start with checking the box.. any play is not good.. I would also look closer at the total toe in.. I only run 1/8 - 3/16 in mine.. and check your front tire pressures.. I run no les than 38psi in mine.

[Tom Goldman]

Even a little play is too much on a P&S type steering box. .... Unfortunately getting parts for them has been difficult recently, altho I was told that Mark Williams is supposedly going to manufacture the parts. .....Check the mount bracket on the frame to see if the holes are elonegated, I've seen this on other Brogies. ......Also check the u-joint, the lower one is on such a severe angle ,it also can wear out. ....Check for runout on the front wheels. I've had as little as .030" lateral run out cause nearly the same vibration..... The r.o. was the result of a more violent than usual wheelstand...... Tom

[555brogie]

Thanks guys for the info.
Tom, you are right about the lower U-joint. I replaced it a month or so ago and it was equipped with a dragster style u-joint made for low weight/low torque applications. It was part of the problem with the slack in the steering. I think I've eliminated everything in the steering shaft itself, but still have a few thousandths run out in the box. I have the SPE box in mine, and plan on replacing the worm and sector gear. I'll also try more air pressure this coming year in the front runners.
Can one of you tell me if I can get by running super gas at a divisional event with the 9" dragster style wheel in the car. Had to go to the smaller wheel due to leg clearance.
thanks
Travis