[Rollo`]

09 328i coupe with 74k miles on it...just started getting a very slight steering wheel shake at 50 MPH.

You can really only feel it right at 50 Mph. Do I need to replace the front control arm bushings?

Can some suspension guru explain why this is the symptom of worn bushings, or if not that, what it is a symptom of?

thanks...

[X_Drive]

Before diving dollars into components, Check your wheels and tires. Vibrations at speed usually indicate that something rotating is not balanced. It could be a wheel weight fell off, a rim(s) that could have been bent/damaged or a tire that is becoming out of round.

As for a worn suspension component, a good indication of wear/damage is abnormal wear to the tires. This can also be accompanied by unusual sounds, such as clucking. Also, when components wear out, vehicle wander can sometimes happen. Or in simple terms, the vehicle will pull or dart in a direction that you do not want it to when driving. On occasion, a vibration can occur if the component is completely pooched.

Sometimes, there is no visual indication and therefore you will have to inspect each component the caveman way. By using your hands and beginning to push, pull, wiggle and manually deflect components both on and off the ground. Just be aware of the safety issues when getting under your vehicle, especially if you are jacking it up.

This is just a cheap and easy way to begin to isolate issues before opening up your wallet and plunking hard earned cash at your car.

HTH.

[Efthreeoh]

I agree with the above post. Check tire balance and wheel condition first.

Regarding the control arm bushings. It's really the thrust arm bushing you are talking about. The non-M thrust arms have a hydraulic bushing located in the forward part of the arm that mounts in the front frame cross member. If the bushing starts losing hydraulic fluid it can cause steering vibration but only under braking conditions. It's easier to just replace the thrust arm rather than try to replace just the bushing. The price difference is about $20 an arm. I lot of folks here move to a M3 thrust arm (I did) when replacement is necessary.

[cdgatti]

mileage and condition of wheels and tires???

[Rollo`]

Wheels and tires are in good shape.

The steering wheel is not vibrating as much as shaking ever so slightly. It reminds me of the shaking my e46 gets when the bushings need to be replaced. It has 150k miles on it and I replaced them at around 70k and again around 145k miles. Although the shaking it does happens at a lower speed and is more pronounced.

I'm going to replace my Akebono brake pads tomorrow and will inspect everything and also rotate my front tires side to side...