I have a '27 Roadster with a torsion bar front suspension. During and after a wheel stand (4 to as high as 6 inches) the front wheels go into a wobble that can last as long as 150-200 feet out. The steering wheel shakes bad enough that it nearly vibrates out of my hands. The videos look terrible, real scary and really terrible.

The front axle is new and thicker than the original axle to keep it from flexing or bending. It has 9 degrees of caster, zero degrees of camber and zero bump steer.

The spindle steering arms are new, level to each other and tight. The tie rod bolts directly to the steering arms with no spacers between them, just the heim ends and specialty washers.

Question: Could spacers possibly improve or eliminate the wobble?

The front wheel bearings are new (ceramic) and tight.

There is ZERO play within the new king pins and new bushings. The spindles are perfect, zero wear or slop.

The tie rod and heim ends are new, the toe is at 1/16 in. I have moved it to 1/8 in, but that did not stop the wheel wobble so I went back in to 1/16. The car steers perfectly at high speed, never wanders.

The drag link is new as are the heim ends, the heim type specialty washers and grade 8 hardware with ny-locks.

I use a special Meziere manufactured washers (everywhere) that have a tapered design specially for heim ends. Nothing is binding.

The pitman arm is new, snug and adjusted for equal turning radius in either direction. I've moved the drag link location from top to bottom, zero change.

The steering box has all new parts in it (sector shaft, worm gear, bearing, etc.) and is secured to the frame with grade 8 hardware. It is totally stable. I installed a second steering box, that changed nothing it also produced the same front end wheel wobble.

The steering shaft to the steering wheel has virtually zero play. The steering shaft universal joint is new and tight, zero side play or slop.

I replaced the front wheels, the Hoosier tires are new and balanced (first bubble and then spun balanced), dead on with a zero. I know, overkill!

This wobble has gone on for several months and has slightly improved but it's still there. I can't find anything else to change, everything is new. The videos still show that the front wheels are moving back and forth although not as bad and I can no longer feel it in the steering wheel.

Once I get beyond the 200 foot area it steers perfectly, zero vibration or steering wheel play.

I'm out of ideas and items to change. Someone with more experience in front axle geometry might be able to help.

Bob

This message has been edited. Last edited by: RPROGAS,

Is it possible to add a shock damper that would act to dampen the wheel wobble....

It's a solution many Stockers and SS'ers use.

My buddies '67 Chevy II did it sometimes but usually only lasted a couple seconds...

I drove it once when it did it....Did not like that !

I put a Bilstein on my motorhome to replace the cheap stock one....Stops the death wobble from roads being rough...

Been a long time ago but when I had a 27 Roadster It had a steering shock damper on it. Just a thought

Shock valveing and bump steer maybe? I'm no expert on torsion front ends. Harold Meziere maybe a souce. you know where to find him!

Nine degrees is a bit much. I run seven degrees in my altered. Angled with top of spindle toward rear. Also splines on radius arms to torsion bar can get sloppy. Modified my radius arms to pinch down like this.

Sorry don't know how to post a picture

Bob, yeah that is not good. I broke late in a season, had 1 points race left, in 2nd place. A good friend loaned me his beautiful 66 Nova, and he warned me about it. Sheer death wobble, but only for a narrow speed range, my guess was around a 10 MPH band somewhere between 65-75 MPH. Thankfully it passed through that range fairly quickly, both accelerating and slowing, but it was a few seconds of outright terror at both ends of the track. Not a mild wobble at all. Car behaved perfectly beyond that, up to 128 MPH. I know he eventually solved it completely, don't know (or maybe don't remember) what the culprit was, it seems like something not real expensive, and also not what you would have expected. He threw everything at it that you have. I will try to call him this evening and pass along what info he can share...

Thanks for the suggestion Rich, I will see if I can adapt a steering damper in a way that it clears the body and nose piece.

I ran the car for several years without the wobble so it is puzzling why it should start now. Something changed. This only happens at low speed, once it get rolling it stops, probably two seconds out, maybe a bit longer. While it's shaking most smart guys would have the tendency to bailout.

Last week I lowered the wheelie bars so the front end could only get about an inch off the ground. The wobble was hardly noticeable but you can still see some of it in the videos. Probably not a good plan for a Pro Tree.

I will look into the steering damper.

Bob

I hope your caster and camber numbers are backwards. As in 0 camber and 9 caster....?!

Sorry that is to say 7 degrees of caster.

When you jack the car up in the front on a level surface do both wheels leave the ground at the same time? Which ever wheel touches the ground first after a wheelie the caster turns the wheel in the opposite direction of the wheel touching the ground first. It can then go into a cyclical wobble. A perfect square wheelie with both wheels taking the weight at the same time will not wobble.

quote:

Originally posted by bry-war:
I hope your caster and camber numbers are backwards. As in 0 camber and 9 caster....?!

I believe they are and that was my thought also. LOL

Steering stabilizer for a dragster or altered with R/P. 7 different loads by turning the end adjuster. Used for early productions Bikes.

My Camaro went for years and never had a problem until it did. The steering went into the death wobble and I couldn't hold onto the wheel. It's very common on F bodies like mine and the biggest fix is a steering stabilizer. The one Quay sell is an early VW shock with weld on brackets. The VW steering stabilizers are available through any parts store.

From the sound of it I would think loose tie rod end or something like that. Since you have went over all of that I would measure your toe in at static height, then raise it up until wheels are of the ground and see if toe in changes?
Also check if the front wheels turn any as it goes up.

Check to make sure the steering box bolts are tight. Seen that and it was a handful and simple fix.

A dampener may help to but since it worked fine in the past with out one, why would it need one now?

All my 23 alterds I built in the 80's were torsion front with straight axel. Used a stabilizer right from the start. Tab on axel and a collar on the link between the steering arms to attach the other end to. O camber,8 degree caster, .100 toe in 120 wheelbase. You can play with the toe in as there is really no change cause of the straight axel. You just do not want toe out. That being said would start at .100 and work it back a little to .060 but only trying to get the least amount of tire scrub.

SLICKSTER is right about the Toe-in you must have a little or it is all over the track and faster you go worse it gets. Not sure that is the issue here though.

But I would jack up the front end and check the toe -in as the front comes up to see if it changes.

If there's nothing loose I still contend that the issue is with the timing of the two wheels coming back to the track surface. Toe would be noticed at the top end. A car with appropriate amount of caster for the speed obtained and toe in set properly will not wander.

This car never wonders around once it's in high gear, it's extremely stable. Adding a few degrees of caster (now at 9 degrees) quickly fixed that issue. The problem begins with the drop of the front end after the wheel stand. Watching the videos there is a very small amount of front wheel movement while they are in the air, but once they come back down it's far more evident. The higher the wheel stand (4 inches) and the further it drops the worse the wobble so I keep the wheelie bars fairly low and slow the throttle stop speed.

My next plan is to open more time working with the rear shocks to slow and soften the hit when the tires come back down. Once they are down and the car travels about 200 or so feet the wobble stops. This is one very big balancing act with a very narrow suspension tuning window.

If I could figure out a way to post a video from a Divisional (S/G) race at Fontana two years ago you would see what I have been dealing with. In that video it continued out to nearly the 330 cone. My computer skills end with pushing the "On" button.

Bob