steering wheel shake w/M II

[40cpe]

Heidt's M II with stock upper and Heidt's pressed steel lower control arms. 4 !/2 degree caster. The tires/wheels check true, balance rechecked. 15X6 wheels, 3 1/2" backspacing. Lower control arm down at the outside 1 degree, steering arms slant up at the outside about 3 degrees.  No lose parts or slack found by front end mechanics. Manual rack.

I'm chasing a driveability problem. I get a quick shake of the steering wheel when I hit a rough road crack or other irregularity in the road at any speed. Above 70 mph the steering wheel shakes like a tire out of balance. I don't feel a shake in the car, just in the wheel. Occasionally on some road surfaces it doesn't shake at those speeds, but mostly it does. I called Heidt's engineering and sent pictures. He said the upward slant to the steering arm is because of the caster setting, but typically 4 1/2 degrees is OK, more caster will only increase the upslant. He didn't have any other suggestions but to try a bump steer stud kit. He said that it might be just enough to help.

I'm looking for help. I know you guys have lots of experience with this setup. It is in a '40 Ford. Any thoughts on the bump steer kit or other possible problem areas would be greatly appreciated. Fixing this would make long trips much more enjoyable.

Thanks, Gene

[papastoyss]

Are the rack mount bushings worn or deterioated? Do you have a vibration damper in the steering shaft or just u joints & shaft? Just throwing these out, I've never had this problem, altough  I had a vibration like tire out of round or balance once  that went away when I took off the 9" rotors (Taiwan) & installed 11" rotors.

[40cpe]

Are the rack mount bushings worn or deterioated? Do you have a vibration damper in the steering shaft or just u joints & shaft? Just throwing these out, I've never had this problem, altough  I had a vibration like tire out of round or balance once  that went away when I took off the 9" rotors (Taiwan) & installed 11" rotors.

The car has been on the road since '95, it's done this thing from day one. I put the A-frame type lower control arm on about three years ago trying to help this problem. I changed the steering shaft to a sliding double D with the upper joint being an anti-vibe type at the same time. I don't see how they can help much, it is just a piece of rubber sandwiched in. This isn't a vibration, it is a shake in the steering wheel. I've replaced the rack bushings since then. They don't appear worn or deteriorated. I do have the 9" 5-lug rotors, though I don't see how they would cause the sharp * when hitting a bump at lower speeds  

Thanks for the thoughts, keep them coming. There has got to be an answer. I'd drive a thousand miles if someone could fix this.

[wayne petty]

ok...   is this shake a a single pull to the side  then back to center..

or a continuous back and forth after it starts...

i did not get a chance to look it up as i am not familiar with the various types of lower control arms...  i take it that this one has the long bolt and bushings on front and and rear of that threw bolt...

instead of the single bushing and a strut rod type of bushing....

what i am thinking is the suspension is deflecting  as you hit the bump and it pulls on the tie rod which is attached to the steering linkage..  

if you get a constant shaking after it starts...    my thought it to have someone drive next to you at speed and watch the tires to see what they are doing...  

it could be that the tire balancer was out of calibration...  or the wheel center where the tire balancer is centered is not on center with the lug bolt circle..   so once you input the excess motion... it continues at that resonant frequency...

[enjenjo]

Bias or radial? how much toe in?

[Mikej]

Any abnormal tire wear? Wore on the inside, or cupping?  Broken or weak shock?

[40cpe]

ok...   is this shake a a single pull to the side  then back to center..

or a continuous back and forth after it starts...

i did not get a chance to look it up as i am not familiar with the various types of lower control arms...  i take it that this one has the long bolt and bushings on front and and rear of that threw bolt...

instead of the single bushing and a strut rod type of bushing....

what i am thinking is the suspension is deflecting  as you hit the bump and it pulls on the tie rod which is attached to the steering linkage..  

if you get a constant shaking after it starts...    my thought it to have someone drive next to you at speed and watch the tires to see what they are doing...  

it could be that the tire balancer was out of calibration...  or the wheel center where the tire balancer is centered is not on center with the lug bolt circle..   so once you input the excess motion... it continues at that resonant frequency...

The lower arm you describe is the one, but it did it with the strut rod. When I hit a bump it is only one sharper *, but at higher speeds it is a fairly constant shake like a wheel is out of balance. Occasionally it runs smooth at the same speed and then starts back shaking. I'm on the third set of tires, the first ones developed dry rot looking cracks, the second set had one separate, the third set is new. none of the tires showed any abnormal wear. I drove the new set to Knoxville and had them balanced again to eliminate the balance question. I have aftermarket steel wheels with dual bolt pattern that have been on the car since new. Putting a pointer at the rim doesn't show any wobble. 9" rotors have been on the car since new.

Shocks are Monroe Gas that are relatively new. Again, it's done it always. The tires are P205x70 radial Perelli. The toe in is 1/8".  The card drives straight without fighting it since I went to 4 1/2 degree caster. It's just when I start a long trip it becomes a nuisance.

Thanks for your interest and comments

[exsedan]

Once had a similar annoying "shake" in the front of a '36 Ford with a MII. Turned out to be an out of balance rotor. Found it by removing all of the grease from the rotor and the bearings, then reinstalling the rotor without the grease seal or grease with the nut being just barely finger tight. Spun the rotor just slightly and observed where it stopped and marked the bottom with a ink mark. It stopped in the same place each time and was out of balance enough that you could turn the rotor 90 degrees and the heavy spot would return to the bottom each time. Might give it a try, it's a free and simple check.............EXSEDAN

[wayne petty]

any chance of getting someone to drive beside you and watch what the tires are doing?

is there any slack in the strut rod bushings...?   most have an internal spacer to stop them from being over tightened....  any chance of levering the suspension with a pipe carefully... and seeing how much play there is in the strut rod bushings?   perhaps adding a washer somehow to crush the strut rod bushings a bit tighter..   warning.. this may slightly affect caster settings... maybe toe in settings...  but this is a see if it is this part that is causing the problem...

how much play is there in the inner tie rod ends?   i have had to change a few on these mustang 2 and fox body set ups...  the inners are not lube able.. they just wear out...    

got a big pair of channel lock pliers???  can you squeeze the outer tie rod ends???  see if they compress in... if so they might be worn also.... i usually test them with the wheels on the ground and someone behind the wheel...   brakes on...   wobble the steering wheel back and forth about an 1/8 of a turn... fast.. while i place my hand on top of the tie rod ends... if the top moves and not the steering arm.. the tie rod end is bad..

 when suspensions are built.. there are sometimes problems with harmonics...  sounds like you have that problem....
so changing the tension/tuning on something might change the response frequency...   which is why i think that tightening up the strut rod bushings by adding a washer to the stack... (that fits over the inner tube) might help...

[58 Yeoman]

Have you tried different wheels?

[41woodie]

I'm in the middle of the same problem, front end is all nearly new and had not been a problem.  On the way to the NSRA in OKC developed a shake around 50-55.  Checked everything for loose, worn etc. no problems found.  Pulled the front wheels/tires and replaced them with a set from another car, no more shake.  The tires are Coker's WWW radials one has a separation the other is very obviously out of round.  The tires are on their way back to Coker for warranty coverage. Hopefully that will have a happy ending.
The out of round tire was a minor annoyance, but the separation really caused a bad shake.  Before I returned the tire to Coker I had a tire shop check the balance. The tire with the separation was 7 ounces out of balance.
You might pull the tire/wheels and have them rebalanced and check for separation etc.

[C9]

Was the caster set on an alignment rack?
Or done at home?
Caster is measured against a level floor surface and not against a flat spot in the frame.

I'm guessing there is no way you could have gone into negative caster - spindle tops toward the front instead of positive caster with spindle tops toward the rear.

I hear that negative caster makes solid axle cars behave in strange ways and the same would be true for an independent.

Is it possible you have a bent wheel that's not running true?
You can check this with a jackstand and wire pointer or go so far as to put a dial indicator on the wheel flange.
Both ways work fine.

Are you running a sway bar?

I was going to suggest you had an out-of-round tire, but with three different sets probably not.

How about steering U-joints, quality stuff with no play?

Could the steering U-joints be loose?

Are all of the wheel balance weights on one side of the wheel?
If so, you may have an out of plane imbalance.

How about steering wheel play?
I know that racks allow very little play - if any - but if so I'd look into installing a new rack.

Any chance the wheel is sitting on a rivet or other protrusion on the flange mounting surface which would make it wobble?


Granted, some shot in the dark stuff, but....

[Pep]

Sounds like bump steer to me..Can you check the rack pivot point against the  intersection line of the upper and lower wish bone pivot points. It would be visibly noticable if it is way out.

[40cpe]

Wayne:  there are no strut rods. I had the same thoughts and tried the washer trick on the bushings. I eventually changed to the A-frame style lower arm to eliminate the struts.

41 Woodie: Tires have been balanced by two shops, wheels and tires checked for out of round with a pointer. Maybe 1/16th is the most I could find anywhere. The only other wheels I have here are too small in the pilot hole to fit my hubs.

C9: It's been aligned several times, all professionally on racks. Wheels and tires checked with pointer.

Pep: I've been thinking bump steer all along because of the sharp * in the wheel when when I hit a bump. The car drives good except for the * and shakes. It doesn't dart or wander.  The shaking doesn't transmit to where you feel it in the car, it just shakes the wheel. An imaginary line through the ball joints to the ground looks like it would hit inside the center of the tire at the ground. I posted about this a while back asking if 4" backspaced wheels might help. The consensus was that 3 1/2" was OK, so I didn't change them. I have pictures of the suspension with the car on the ground, but see no instructions on posting. There is about 4-5 degrees difference between the lower control arm and the steering rod. That is the reason that the Heidt's engineer suggested the bump steer studs to adjust the steer arms down. I've talked to Heidts several times about this and they are always very noncommital and say that they have never heard of this before. Yeah, sure. Thanks to you all for helping me scratch my head over this

[Mikej]

Have you tried different air pressure? If you have bump steering issuses, you should fix those.