Help Needed: Steering Wheel Vibration / Shimmy

[grantmax]

Hi Everyone:

I have been chasing an issue that is driving me crazy—steering wheel vibration / shimmy at freeway speeds (65-75 mph). The vibration comes and goes as I put steering input into the car or hit uneven patches on the road.

Before we get into it, I’ve had this on other (modern) cars in the past and a wheel rebalance has always fixed the issue. Suffice it to say, I’ve tried countless balance places, wheels and tires. And yet, the problem persists.

Background on car: The suspension has been completely refreshed with genuine Porsche bits. The shimmy was present on my flat 6s (CN36s), deep 6s (CN36s), original steelies (Vredesteins) and now on my Group4 “steelies” (Vredesteins). This leads me to believe it is something on the car.

The current thinking: It could be the hubs. I have a set of G body hubcentric hubs going on the car. Disappointingly, the Group4 wheels (like the OE steelies) have an 84mm center bore. To address the gap between the hub and wheel, I have a set of centering adapter rings en route. Not feeling confident, so I’m reaching out to the experts here.

Any ideas, suggestions or thoughts are welcome. This problem desperately needs a solution. Thanks in advance.

Video and details in Post # 8.

[jim amato]

Here is a recent thread on this: https://www.early911sregistry.org/fo...ht=ball+joints

[lkadams]

Thanks Grant for asking the question and thanks Jim for the link. I have had a very similar problem (shimmy comes and goes) so if I ever get my Mercedes off my hoist, a new set of ball joints may be in order.

[tom1394racing]

Try swapping the front and back tires and see if it makes any difference. A friend of mine recently had this problem at 75-80 MPH. He swapped tires front to back and the problem went away.

[Dexterpix]

Grantmax,

Not sure of your location (geographically) There are tire shops that can balance the wheel while mounted on the car. This can help correct for any in balance in the rotating assembly (hubs, rotors ect).

Has the car been aligned properly?
Were there any odd wear patterns on the tires you have removed/run?
Is there any play in the wheel?

Problem with most wheel balancing machines is they only spin to 55-60mph, speed beyond that can still induce a vibration.

Joe D

[grantmax]

Thank you for all of the tips and feedback!

With the G body hubcentric hubs on the car, we were able to run 16” hubcentric Fuchs and confirmed that the problem is not on the car. The 16s ran smooth without vibration. Having this information in hand, we spun the offending wheels/tires on the car and noted lateral (left to right) movement/wobbles.

Does this suggest a balancing issue or are the tires simply out of round? If the latter, is this a problem that can be corrected by another (proper) balance or are these tires done for?

Regarding location, I am in Los Angeles and am aware of our friend Nate Jones in Signal Hill. However, with the noted movement, I am inclined to avoid wasting more time on this issue and would prefer to race to the finish line, cost be damned.

Important Note: The wheels are brand new, so we can rule out bent wheels. It’s the tires.

[HughH]

I would not rule out the wheels because they are brand new.. IF you are going to change out the tires as you seem to be saying, can you remove the tires from the offending wheels and spin them up on their own just to make sure they are not out of round in some way
it would be a waste to fit new tires and find the same problem

[grantmax]

Video of rear wheel/tire is below. This is obviously not the cause of my steering wheel wobble/shimmy, but evidence of how the other tires are behaving. I’m told the lateral runout on the fronts is just as bad, if not worse.

Seeing as we have numerous wheels behaving badly, I’m thinking a better balance is the right place to start.

Video: https://youtube.com/shorts/G9oUg7SEUWQ?feature=share

[1969911T]

Have you checked the front wheel bearings? Not being tight enough could be an issue.
Steve

[G50911]

i chased something down like this on 2 cars. both had different issues.

car 1: 1971 hotrod, after countless attempts to balance, rebalance, road force balance and rotating, one of my tires (michelin TB15) was out of round. something i least expected from a company like michelin and for this premium tire. i sent it back with a video and they sent me a new one. vibration gone.

car 2: 68 hotrod, same process as the 71 but everything checked out. after careful inspection of the front suspension, tie rods, ball joints and even testing my hubs for run out, i found that my bilstein collar worked itself loose. i remember i tried to torque it down as best i could with a small hammer and punch since i didn't have the collar wrench but apparently that wasn't enough. i found out it needs to be torqued down at 90 ft/lbs. i picked up a proper wrench and torqued both sides down and voila, vibration gone.

hope this helps!