Relentless steering wheel shimmy - Part II

[OldStyle]

Originally Posted by 1 Lucky Texan

17. Figure a bad rim/wheel would be consistently wobbly?

yeah, wondering about run-out. Also, some bad threads on a wheel stud or cracked/bad lug-nut.


(just more brainstorming)

That's what I thought on first read. But I'm sure they checked the run-out with the wheel off the car.

OP, Have you grabbed the wheel with the tire mounted to the hub but off the ground and shaken it front to back and top to bottom? Felt for movement? results?

Sorry if this has been answered already....

[DavidPeab]

Yup, I checked again last weekend with the tires on and again with them off - double checking tie rod ends/ball joints. Very solid.

I order a dial indicator with a magnetic base and will check the rim runout when it arrives. The car sat for three years, so I replaced the tires. I'm wondering if a. The previous owner's fender bender warped a rim and the Goodyear guy did not catch it. or b. Just sitting for so long has an effect on alloy wheels - unlikely, but the only stupid question is the one unasked - or any question from my wife about whether her pants make her look fat. lol

[1 Lucky Texan]

maybe I'm not thinking right, but my guts tell me, the farther from the hub a 'problem' is that could cause this shimmy, the more likely it would diminish with heavy braking. Like, something with the rack or tie rods, or with a strut mount' the forces and 'dynamics' under braking would cause all the tolerances in the various connections and moving parts to shift to the other extreme of their (limited) clearances/range-of-movement.

I'm betting you might even feel this in reverse. This just seems like it's at the wheel(s).

I guess it's impractical to rent or borrow 4 wheels to try.

[1 Lucky Texan]

Originally Posted by DavidPeab

I tried heavy braking and it got a bit worse.

OK, could you do a 'heavy braking' test a few times on pavement, then compare the same test on dirt or gravel? Seems like if the severity of the 'shimmy' is diminished on dirt or gravel, we may be able to implicate tires and wheels(maybe the rack ?). If it feels the same, it 'may' point to brakes, rotors, hubs, other 'stuff' unrelated to 'steering'.

trying to differentiate from 'steering' system vs 'run-out/vibration' problem.

I dunno, kinda hard to explain.

[DavidPeab]

I'll start looking for the right times and roads to do the braking tests on and let you know how they turn out. It makes sense that any loose stuff would get crammed against solid stuff when heavy braking occurs and therefore stop vibrating. Newton's first law applies here. The outside force is the brakes.

I'm betting you might even feel this in reverse. This just seems like it's at the wheel(s).

I'll also start looking for a place where I can go backwards at 65 MPH. Just kidding, of course.

I'm going to move whichever wheels have the least runout to the front and see if that helps. Still waiting the gauge and stand.

[DavidPeab]

I finally got around to using my new dial indicator for the runout tests on the wheels.



If you can see the line graphs, they show the relative runout between the four wheels. The flatter the line, the less runout, and the better the wheel. The dotted lines represent the front wheels. It is pretty obvious that the right front wheel was the worst. Surprisingly, the back left wheel was the best. Two tire shops I went to recommended putting that wheel in the back because it required more weight than the other three. I rotated front to back on both sides based on my findings and went for a test drive. AND... There was still a much smaller and shorter lived shimmy. But some shimmy none the less.

I had the opportunity to brake from 70 mph down to about 50 mph today and wasn't able to tell if the shimmy was reduced by the hard braking or just because I was going under 65 mph. I'll look for more suitable roads and times to test. If this test does not tell me something pretty conclusive, like a bad strut cap or more likely the rack, then I am just going to live with the intermittent high speed shimmy. My wife and children are beginning to worry about me like Nash in A Beautiful Mind. lol After all, Its an old car.

[OldStyle]

Now that you have that base line recheck the left front, with the best wheel installed, and see if it still has that runout issue. Maybe the problem isn't with the wheel.

.

[1 Lucky Texan]

Originally Posted by OldStyle

Now that you have that base line recheck the left front, with the best wheel installed, and see if it still has that runout issue. Maybe the problem isn't with the wheel.

.

^^^good idea. Those graphs have all the accumulated errors from hubs, rotors, AND wheels. Heck, even dismounting rotors and/or wheels and rotating them 2 studs, might change the curves.

are there any published limits for run-out?

[DavidPeab]

Maybe the problem isn't with the wheel.

Correct. Rechecked the wheels and front right was still off. Left was fine So it is something in the front right suspension. I took a test drive and leaned over to the passenger (right) side and felt vibration during shimmy there when I felt none on driver's side. Please see the stuff I have tried on page 1 of this post and let me know what I should check or re-check.

[DougNuts]

It sounds to me like you need a new steering rack. I'm going through the same thing right now with one of my cars (not a Subaru).