Help with tracking down a mild steering wheel shimmy?

Discussion in '2005+ Mustang GT 4.6L Tech' started by 1950StangJump$, May 3, 2021.

  1. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    2008 GT. Been unable to be rid myself of a slight highway steering wheel shake for years. Doesn't really manifest itself until 50+ MPH, and it doesn't go away as speed climbs. IT IS ROAD DEPENDENT, i.e. glass-smooth roads produce virtually no shake in the steering wheel, while bumpy roads seem to make it considerably worse. At times, I have rationalized that it was nothing more than increased vibration from the lowered suspension and low profile tires but, in the end, I don't think its "normal." I have noticed no bump steer issues.

    Here's the changes as succinctly as possible. Most of the changes were not specifically to address the shimmy, but lots has been done:

    • Purchased the car 2+ years ago. Stock suspension but 20" rims. Found one of the rims bent, so I replaced all rims (with new 20" Foose rims) and and installed new Nitto tires. Everything roadforce balanced then (and multiple times over the past two years), but the shimmy didn't change.
    • About 18 months ago, installed Pedders adjustable coilovers to lower the car. At the same time, I installed camber bolts and a BMR adjustable front sway bar. Car aligned within specs. No change in the shimmy.
    • A year ago, I decided to build up the motor. In the process, I found the A-arm bushings were bad, so I replaced both A-arms with the upgraded GT500 A-arms. I thought I might have stumbled upon the true shimmy problem, but it had no effect when replaced and car aligned.
    • With the new motor installed, I put in a BMR lowered K-member, radiator support, cross brace, etc. Car aligned within specs. All tires roadforce balanced again. Still no change.
    So, as you can see, most of the front suspension, wheels, and tires, have been replaced over the years, with no real change to the shimmy. At this point, I'm down to the steering rack and tie rods, and those can be changed out for $300 in parts (plus alignment). But, I do have a car lift, and with the car up, I can get ZERO play in the rack or tie rods when I grab and tug on them, so it feels like replacing them would be a shot in the dark.

    I'm at a loss.
     
  2. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

    39,353
    2,214
    if you have a square set up have you rotated the tires to see if it changed at all?

    I realize you said new tires/wheels + roadforce... but it's a simple test
     
  3. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    Thanks for the input . . . but it's a staggered setup . . . 235/35/20 on the front, 295/35/30 on the rear
     
  4. msvela448

    msvela448 forum member

    266
    92
    Since you have Foose wheels is the bore size in the center of the wheels the same size as your rotor hubs... You shouldn't rely on the lug nuts to center the wheels. Take some measurements of those diameters and try a set of hub-centric rings if there is a difference.

    https://us.hubcentric-rings.com/why_hub_centric_rings/?src=intpopup

    Sent from my SM-N975U using Tapatalk
     
  5. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    Good thought! I should have mentioned that I explore that possibility also, but they are the correct bore size
     
  6. Laga

    Laga Member

    503
    204
    Just throwing out ideas here. Since it is road and speed sensitive, check center hanger on driveshaft. It could be worn out and causing a vibration. Also, how are your front brakes? See if a caliper is not releasing or a rotor is warped. Then check for play in front wheel bearings.
     
  7. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    Thanks for the ideas.

    In the last two years, I have also put in a Magnum XL and one piece driveshaft. Both have been out a couple times over the course of the build. No difference.

    Have also put in new brakes, Brembo style calipers, and rotors .... no change. Also, no change in the shimmy when I hit the brakes, like you'd expect is the rotor was warped and dragging.

    but ... I haven't not the wheel bearings. What's a good way to check them? They make no noise, if they matters, and I can get no wobble by grabbing the wheel and shaking when on the lift
     
  8. MrBhp

    MrBhp Member

    571
    363
    I chased a shimmy in mine. Turned out to be a tie rod end.
     
  9. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    Could you tell the tie rod was bad from underneath the car?
     
  10. Laga

    Laga Member

    503
    204
    Not the wheel bearings then.
     
  11. MrBhp

    MrBhp Member

    571
    363
    There was just a slight bit of play when I bumped the tire while on jack stands. It didn't appear to be the tie rod end, but it was.
     
    1950StangJump$ likes this.
  12. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    I'm going to end up dropping the 300 bones just so I know I tried everything ‍
     
  13. OX1

    OX1 forum member

    266
    50
    What correction was required during roadforce? If a lot, maybe the tires were just not round.
    Would be odd two sets of tires had this, but I've had many new tires not round in the past 8 years.

    Way more than you think there would have been. I was allowed to work OT as much as I wanted for 9 straight years. I went crazy with multiple sets of tires for almost every car I own (IE, mustang had winter, summer, drag, and road course sets), which is the reason I had so much experience with out of round new tires (plus I have my own machines, so it's kind of easy to spot spinning on balancer, especially when it wants a bunch of weight with news tires).
     
  14. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    Thanks for the input.

    The front has 235/35/20 Nitto 555 G2.

    I don't remember how they road balanced the first couple times. This last time, they showed in the low 20s (not sure the unit of measurement?), which I know is not ideal, but I was told it wouldn't cause vibration. Ideal is less than 15?

    The machine told them they only stood to lower the number by 1, so they let it be and just ensured the balance of correct. Thoughts?
     
  15. Sterling

    Sterling Junior Member

    5
    0
    Could be a tooth broken in your rack and pinion. Have you ever had the steering shaft out? You could have put the bolt in backwards when you reconnected it. I'm talking about the bolt that locks the steering shaft into the rack and pinion. On one side there are threads, on the other side there are not. If you put the bolt in backwards the bolt really doesn't tighten anything. Easy thing to overlook.
     
  16. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    The bolt for the shaft has been out several times, but it is definitely in the correct way . . . yea, the bad rack-and-pinion is as good a theory as any. Sure hate to just drop the $ for a new one when I don't know the old is bad, but I'm sick of this shit . . .
     
  17. Sterling

    Sterling Junior Member

    5
    0
    LOL. You're telling me. Working on my car has always been difficult and frustrating. I had sort of the same issue as you and did the EPAS swap from a 2014.
     
  18. DieHarder

    DieHarder Member

    433
    193
    By chance do you have star washers holding your rotors on? On original wheels they often put on one or two on the studs to hold the rotor. I had them on mine and didn't realize when I changed wheels that they were now interfering with the back of the wheel sitting flush to the rotor. Couldn't get rid of the shimmy no matter what I tried. Finally put the front up on jacks and checked the run out. When I pulled the wheel the old star washers were still on. Removed them and never had a problem since.

    Couple of other possibilities: 1) Out of balance rotors. 2) Tie rod/bushing and tie rod end. Just had mine replaced when the shop found they couldn't align the car properly. Since yours aligns okay I would look at the other issues first. 3) Bad rims. Unfortunately, my experience with wheels hasn't been ideal. I've purchased at least three sets that were out of round. One set I had repaired so they're serviceable. The other I just sent back and the third were brand new out of the box. The entire face of all of them were offset from center about an 1/8". Can't make this stuff up. Moral of the story. Avoid cheap aftermarket wheels.
     
  19. 1950StangJump$

    1950StangJump$ forum member

    943
    96
    Great thoughts, thanks. The star washers are gone, and the rotors have been changed three times over the years (for different reasons) with no change in the shimmy.

    The Chip Foose rims were brand new. I realize that doesn't necessarily mean they are absolutely true. But, not one of the 3 times I had the tires rebalanced did anyone mention they observed anything .... which I also recognize is not an absolute guarantee.
     
  20. msvela448

    msvela448 forum member

    266
    92
    If you can... Temporarily (like for an hour) borrow a set of wheels and tires from another friendly Stang owner and see if the problem goes away... If it does then it's your wheels and / or tires. If the problem persists with a different set of wheels and tires then it's something in your steering or suspension.

    Sent from my SM-N975U using Tapatalk
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.