Steering Wheel Shimmy, Slight vibration Options

[Mowog4]

I have a slight vibration in my steering wheel, it is very minor but noticeable. It does not get worse with speed, but I find it annoying. Every suspension piece on the front end of the car has been replaced, new struts, new wheel bearings, etc.. I thought, possibly it was a problem with flat spotting of tires, but new tires and wheels did not make a difference I see online there is a steering stabilizer, that is the only thing I haven’t changed down. Can anyone tell me what that does?
Thanks
Ed

[Superhawk996]

You’re not going to like my answer.

Without driving your car or putting some instrumentation on the car to measure what is occurring, this is an opinion from a guy that spent his career doing chassis engineering.

The spring rates you’re using are very high and are going to drive a lot of road input into the chassis. This is just a fact when spring rates increase. Those spring rates are well over double the OEM spring rates.

914’s don’t have much road isolation to start with. It is a good sign that you used factory rubber bushings. Symptoms you describe would only be worse with urethane, Delrin, or god forbid heim joints.

The turbo tie roads are a very direct connection into the steering rack with zero NVH isolation. This is going to drive road input and vibration right into the steering wheel. The steering is very precise with Turbo tie roads but degraded NVH isolation the tradeoff.

I say this largely based on the fact that you’re saying the steering wheel isn’t oscillating and that it occurs across all speeds from 30mph on up.

There are two things you could try but they probably won’t help:

1) On car wheel balancing. Shops that can do this are getting hard to find. The advantage of on-car balance is that it can compensate for small imbalances like 911 brake rotors that may not be perfectly hub centric.

2) Road force balance of the wheel and tire assembly. Hunter road force balancers can compensate for tire harmonics and spring rate differences within the tire carcass. Based on your descriptions this is a long shot because tire radial 1st harmonic issues usually present at 50-60 mph, and tire radial 2nd harmonic usually vibrates more at 25-35 mph. Based on your description of vibration not varying with speed, this probably isn’t going to help. It may slightly - but I don’t think it would solve your complaint.

If you are comparing the vibration level and refinement of your 914 to a modern road car, you are going to be disappointed.

The other suggestions here about making sure the rear lug centric wheels are mounted properly are valid but again given how the chassis is set up with high spring rates, I don’t suspect that is what you’re complaining about.

If you want to get a real deal root cause, I’d find a shop that is capable of putting an accelerometer on the steering wheel and order tracking it to road speed and Engine RPM. Usually this would be done with a tool like the Vetronix MTS 4000 or similar instrumentation.