Steering wobble, not typical

[Keith509]

Hey,

Been having a weird issue on my 99 Mustang GT, ever since I bought it. Right around 50-57MPH I get a steering shimmy. I don't feel it anywhere in the car or on the seat. I just feel the steering wheel slightly oscillating left to right. It's worse in the morning, tends to fade out later. But it's always there.


So far I've replaced:

3 sets of tires, all road force balanced
2 sets of wheels
Inner and outer tie rods
Alignment
Wheel Bearings(front)
Struts
Ball joints
Steering shaft(MM) and rack bushings
Pads and Rotors all around



What else would be causing this. Can't be driveline/driveshaft related, as it's only felt in steering wheel. It's driving me insane, as I've tried replacing every part that is spinning at that speed. Any ideas?

 

[Danny2v]

I had this when I first got my 02 gt, Everytime I accelerated onto the highway it would wobble pretty bad, even worse coming out of the highway. Instantly knew it had to be my front rotors... After a swap, sure enough it was gone. Have you tried stoping from 60 pretty hard but not hard enough to trigger abs? If it wobbles worse during breaking, has to be the rotors. Either resurface or go pic up some rotors. I was able to get a pair for only $70 which isn't bad

 

[Keith509]

I had this when I first got my 02 gt, Everytime I accelerated onto the highway it would wobble pretty bad, even worse coming out of the highway. Instantly knew it had to be my front rotors... After a swap, sure enough it was gone. Have you tried stoping from 60 pretty hard but not hard enough to trigger abs? If it wobbles worse during breaking, has to be the rotors. Either resurface or go pic up some rotors. I was able to get a pair for only $70 which isn't bad

Hey Danny. I had replaced the rotors and pads with powerstop ones as well. Forgot to add it to the list. Perhaps they were slightly out of round?

 

[Danny2v]

Hey Danny. I had replaced the rotors and pads with powerstop ones as well. Forgot to add it to the list. Perhaps they were slightly out of round?

Could definitely be a possibility as brakes will give problems down the thousandths of an inch so maybe give resurfacing a try. I've never had a defective rotor but I've definitely had a couple bad pads either causing noise or vibrations so it may just be another brake issue

 

[Keith509]

Could definitely be a possibility as brakes will give problems down the thousandths of an inch so maybe give resurfacing a try. I've never had a defective rotor but I've definitely had a couple bad pads either causing noise or vibrations so it may just be another brake issue

As a quick update, took the car out and hit the brakes hard and there is no additional/worse vibration. It's definitely not the rotors. I did check the control arm bushings, and there is some movement there. However, I can't imagine they would cause a shimmy at EXACTLY 55-58mph and then it goes away at 60mph. Thats literally the only thing I haven't replaced yet.

 

[Danny2v]

As a quick update, took the car out and hit the brakes hard and there is no additional/worse vibration. It's definitely not the rotors. I did check the control arm bushings, and there is some movement there. However, I can't imagine they would cause a shimmy at EXACTLY 55-58mph and then it goes away at 60mph. Thats literally the only thing I haven't replaced yet.

Hmm definitely makes you wonder... If that's the only part it comes down to, give it a shot as it's not gonna cost you much. Try jacking up the front wheels, then grab the wheels from the 12 o'clock position, and 6 o'clock, and try to wiggle it. Then grab the wheel from the 3 o'clock and 9 o'clock and repeat... This should help you pinpoint any sort of shimmy in the suspension

 

[Keith509]

Hmm definitely makes you wonder... If that's the only part it comes down to, give it a shot as it's not gonna cost you much. Try jacking up the front wheels, then grab the wheels from the 12 o'clock position, and 6 o'clock, and try to wiggle it. Then grab the wheel from the 3 o'clock and 9 o'clock and repeat... This should help you pinpoint any sort of shimmy in the suspension

Thanks Danny. Yeah I've done all the usual checks, and everything is super tight. LCA bushing is the only thing that has a little movement. I'll take it apart today and mess with it.

 

[Keith509]

So it looks like the tires are flat spotting when sitting a few hours. I jack up the car, spin the front tires, and you can see a hop. Wheel/Rim is good but the tire tread hops. Already had that on 2 other sets of tires. Why do these 275/40/17 tires do this? I read its something with the nylon cap in the tread. Is there any tires that don't use that nylon content?

 

[Mustang5L5]

What brand tires are they? Have you used the same brand tires throughout?

 

[Keith509]

What brand tires are they? Have you used the same brand tires throughout?

I tried Fedeal. Khumo. And now BFG g force. I’m having them rebalanced again today. Possible for rotor to be out of balance? They don’t shake when hitting brakes but could they be throwing off the balance ata certain speed?

 

[Mustang5L5]

I've got the G-force as well. My car sits 3-4 weeks at a time in between rides and I have no flat spotting issues. I instantly hop on the highway and take it to 80 without any vibration from the tires.

What brand rotors are they? Changing to a different wheel doesn't change the intensity of the oscilation?

This is a good one

 

[Keith509]

I've got the G-force as well. My car sits 3-4 weeks at a time in between rides and I have no flat spotting issues. I instantly hop on the highway and take it to 80 without any vibration from the tires.

What brand rotors are they? Changing to a different wheel doesn't change the intensity of the oscilation?

This is a good one

They are powerstop rotors from the kit on AM. Relatively new. Wheels didn’t change much? Maybe a little different speed but always at 50-55 range. Worse in morning. LCA bushings are old but not completely shot.