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Re: Vibration on speed over 55 (archive)

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Posted by Wayne McKay on August 09, 2001 at 16:05:14:

In Reply to: Re: Vibratio on speed over 55 posted by Rich on August 09, 2001 at 14:21:10:

Rich, before you spend a lot on the steering/suspension, it would be a good idea to find a tire shop with the Hunter GSP9700 balancing machine to eliminate the wheel/tire as the cause (about $10 per wheel for the full meal deal - run-out and road force). If the problem still persists, you need to determine if the vibration is steering only (side to side) or suspension only (up and down), or both as was the case for me. I eliminated the side/side with upper control arms and tie-rods and the up/down was solved with new shocks.
The side/side was characterized by a near violent left/right shaking of the steering wheel at the magic 55-60 mph. It took very little disturbance to initiate the shake. For me, the brakes also seemed to help a bit but others have indicated it made things worse.
After that was eliminated, the remaining up/down vibration generally required a bump to initiate it and was more easily started with lesser and lesser bump size as the speed increased. Hitting even the smallest of bumps while turning left would start things bouncing at much lower speeds (less weight on the left wheel). As the LF shock deteriorated further over a period of about two weeks, I began to notice the LF corner sitting a bit lower than the right. Early on I wondered about the shocks and did the bounce test - both sides were within the generally accepted 1 bounce settling criteria. After noticing the sagging, a second bounce check still only produced maybe 1 bounces. Haven't bounced the new ones yet but I no longer feel the bounce test is all that reliable.

If you are definitely sure the problem is in the steering portion of things (left/right shaking), get the weight off of the wheels and tug/pull as hard as you can on everything.
1) Grab the wheels at the sides and shake left and right...look for excessive movement in tie rod ball joints or the idler arm bushing. Look at the ball joint protector covers for problems while you are there.
2) Grab wheels at the top/bottom and do the same...look for movement in the upper/lower control arm ball joints. Look at the ball joint protector covers for problems while you are there.
3) While you are into it, grab the anti-sway bar links and look for anything loose there (not part of the shaking issue but will do the clunk-clunk over bumps). Look at the ball joint protector covers for problems while you are there.
4) Look closely at the upper and lower control arm bushings for sign of leaking fluid - depending upon past replacements, some of these bushings were supposedly hydraulic.
5) This one is harder...with one wheel down, use a pry bar / plank / etc. to push in the unloaded wheel at the bottom and look for excessive movement in either of the control arm bushings.

Depending upon whether or not any of the front end parts have been replaced before, you may want to just go ahead and do them anyway with 150K on the dial. Hope this helps you find the cause.

'88 750iL

I am also very interested in this problem. I have a 1988 735i w/ about 150K miles. My car shakes quite hard at 50-60 MPH only. I own a snap on balancer, and have balanced the wheels several times to no help. I was going to try and balance the wheels with the rotors installed as an assembly next. I do have a donor car with what looks like new front end stuff. When I apply the brakes during the shaking the problem seems to go away alittle.

Vibration (left/right on steering wheel) at that speed is typically due to the upper control (thrust) arm bushings, the tie rods and idler arm bushing in that order (assuming of course you have already eliminated the tires/wheels first). Vertical vibrations are also tire/wheel related followed by worn shocks.

'88 750iL

My 91 750 is in th eshop checking on the oil leak (looks like hydraulic fluid but not sure) and steering wheel vibration on acceleration on speed about 55mph. Shop is called "Eurotech" here in MN ONLY dealing with Mercedes and BMW. Mechanic said usual suspect is driveshaft and wheel balancing issue for the vibration but not in my 750. He is doing a test drive and trying to find out. I will post what else can cause this symptom.
Oil leak is still under detect. Hydraulic fluid reservoir might be the cause pushing out the fluid but double check.

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