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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Car does not feel stable (SOLVED!)



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      10-05-2019, 01:22 AM   #1
Landshark92
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Car does not feel stable (SOLVED!)

I have felt this problem get a little worse over the past year or so but it got a lot worse just recently. When I'm pulling out to pass someone at WOT, the rear has a mind of its own and it is all over the place and I have to make steering corrections to keep the car from steering too much over and beyond the intended lane. The car also tends to wander on the highway after a steering input, and there is a delay before the rear end takes a set and stays there.

These tires have 200 miles on them and I noticed this wear on the right rear tire. The middle of the car is on the left. The left rear tire has wear that is similar but it is only 1/3 as bad.
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With the car on the ground, I crawled under the car as best I could and could wiggle and twist this bar just a very tiny little bit if I grabbed and twisted it as hard as I could by hand. Is it supposed to move at all grabbing it by hand?
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I will have the car up on jackstands tomorrow. Is there anything I could do to diagnose and pinpoint what is causing this behavior?

Last edited by Landshark92; 11-02-2019 at 04:49 PM..
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      10-05-2019, 02:06 AM   #2
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Have you done control arm bushings and ball joints? When the car is Safely on jack stands try pushing/rocking the wheels from 12 and 6 o'clock and seeing if there's any play. Also check if the rubber has any cracks on the bushings and ball joints.
My symptoms were similar to yours.
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      10-05-2019, 04:55 AM   #3
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Quote:
Originally Posted by OvergrownTony View Post
Have you done control arm bushings and ball joints? When the car is Safely on jack stands try pushing/rocking the wheels from 12 and 6 o'clock and seeing if there's any play. Also check if the rubber has any cracks on the bushings and ball joints.
My symptoms were similar to yours.
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      10-05-2019, 11:21 PM   #4
Landshark92
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Quote:
Originally Posted by OvergrownTony View Post
Have you done control arm bushings and ball joints? When the car is Safely on jack stands try pushing/rocking the wheels from 12 and 6 o'clock and seeing if there's any play. Also check if the rubber has any cracks on the bushings and ball joints.
My symptoms were similar to yours.
I think everything is original. The car has 72,000 miles on it now.
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      10-05-2019, 11:43 PM   #5
Landshark92
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I did some testing last night and found the exact symptoms. When I change lanes under heavy acceleration in 2nd or 3rd gear is when I can really feel it. When I change lanes to the right under power, I turn right to change lanes. Then I turn left to straighten the car and finish changing lanes. Right as I finish the lane change and straighten the car, the weight transfers onto the right wheels and the car will shoot over to the left like as if I continued to steer to the left. It only does this when I change lanes to the right. I tried changing lanes to the left and the car felt normal.

I don't know much but could it be the toe control arms? Maybe the rtabs are worn or the subframe bushings are shot. I can't throw money at this problem but I do need to fix it because the car is scary doing slalom type moves.

I will take the advice here and check the control arm bushings and ball joints. Of the five suspension links, which ones have bushings that can deteriorate and cause this?
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      10-07-2019, 06:20 AM   #6
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My car used to do something similar a couple years ago; it was unstable at high speed under any steering input, the back end felt very loose.
I changed rear shocks and rear tyres for brand new Goodyear Assymetric 2 tyres, still same behaviour.

Turned out to be defective front tyres. I put brand new Conti Sport 6 tyres on the front to replace the part-worn Conti Sport 5's and this rectified the issue.

It sounds strange but check all your tyres, not just the rears.
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      10-07-2019, 07:30 AM   #7
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Change rear subframe bushings (M3, poly, aluminium or inserts) + look up the lock-down kit... it has solved this for me and many others... + change your rear shocks as they are the reason for your wear pattern on tires...
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      10-07-2019, 08:18 AM   #8
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Quote:
Originally Posted by OvergrownTony View Post
Have you done control arm bushings and ball joints? When the car is Safely on jack stands try pushing/rocking the wheels from 12 and 6 o'clock and seeing if there's any play. Also check if the rubber has any cracks on the bushings and ball joints.
My symptoms were similar to yours.
This /\

I'd be looking at part no 3 in this diagram...

http://bmwfans.info/parts-catalog/E9...el_suspension/
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      10-14-2019, 10:49 PM   #9
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I had Nitto NT05s that were legitimately bald as slicks in the front. Had this exact same behavior on the road for the couple days I drove it like that. Not sure if that is any help.
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      11-02-2019, 04:48 PM   #10
Landshark92
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OP here and I found the problem. Thanks to everyone that posted their advice and helped me troubleshoot this. And thanks to those that posted that their front tires were the culprit even though it sounded like a longshot. Well, longshot it was but it was on the money this time. I returned the front wheels and tires back to their original positions and the car's stability has been restored.

I probably should have mentioned that when I bought new rear tires right before I started this thread, I also had them swap the front wheels and tires from side to side. When I got my car back, it was a night and day difference. The car was wandering in its lane on the highway, darting left and right when changing lanes under heavy throttle, and not keeping a line during long sweepers forcing me to make small corrections to keep the car in my lane. It was such a mess that a bmw dealership technician wrote that I needed an alignment. He had only driven the car 3 miles to verify that the new turbos were installed correctly, and even he noticed.

The place that I had install new rear tires and rebalance and rotate the front wheels and tires, that did excellent work, advised that I do not rotate the front tires. BMW advises not to rotate tires side to side. I insisted that they rotate them anyways. Now I know why they didn't want me to rotate them.

I think the front tires are worn in with a toe in wear pattern after the 10k miles that I put on them. Then when they are rotated from left to right, the wear that is used to toe in becomes toe out wear. With the front tires wanting to go toe out everywhere, the car has a mind of its own, and that's what it felt like. That's just a theory so it might not be toe out but it certainly is due to tire wear of some kind.

I also noticed that this car is very sensitive to the front tires. I bought the car used and the stock Bridgestones tramlined horribly. Then I had the Pzeros and they were much better at not following every road imperfection. Then I rotated the fronts left to right and the car was all over the place.

With all the suggestions here, I figured it wouldn't hurt to put the front tires back to where they were. On the test drive, even at 25mph, I started to sense the car was back to feeling planted and stable, but I was afraid it was placebo. It wasn't. I can change lanes and pass cars under power again and not have to fight the car. It obeys my commands once more. Thanks all for reading and providing your anecdotes.

Last edited by Landshark92; 11-05-2019 at 06:30 PM..
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      11-04-2019, 11:08 AM   #11
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Hmm, even on shitty Conti DWS tires, I was able to rotate in an "X" pattern and not notice any difference in drive style. Also, rotating from side-to-side still keeps what was the inside of the tire on the right to the inside tire, just now on the left...unless you had the tires dismounted and switched the tires from an inside orientation to an outside orientation, the "toe wear pattern" hypothesis is bologna.

I agree, BMW suggests otherwise, but that's because they'd rather avoid the headache of warrantying such issues altogether; so it's easier to say "just don't do it" as opposed to ironing out the cause in the first place.

Maybe square away proper alignment settings now and try different brand/model tires the next go around..??
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      11-04-2019, 06:29 PM   #12
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Glad it was an inexpensive fix lol
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      11-05-2019, 05:58 PM   #13
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Quote:
Originally Posted by FCobra94 View Post
Hmm, even on shitty Conti DWS tires, I was able to rotate in an "X" pattern and not notice any difference in drive style. Also, rotating from side-to-side still keeps what was the inside of the tire on the right to the inside tire, just now on the left...unless you had the tires dismounted and switched the tires from an inside orientation to an outside orientation, the "toe wear pattern" hypothesis is bologna.

I agree, BMW suggests otherwise, but that's because they'd rather avoid the headache of warrantying such issues altogether; so it's easier to say "just don't do it" as opposed to ironing out the cause in the first place.

Maybe square away proper alignment settings now and try different brand/model tires the next go around..??
Draw a piece of paper with a diagonal line on it, pointing to the upper left. This represents the right tire with toe in. Now rotate that piece of paper 180 degrees and then place it in the position of the left front, the diagonal line still points to the upper left but since it is now on the left side, that would be toe out.
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      11-05-2019, 06:10 PM   #14
Landshark92
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I did actually think to blame the DWS-06 tires at first. They reviewed excellent but there was always this soft sidewall characteristic that everybody mentioned. Made me think the sidewalls were so soft that the rear tire was not transitioning quick enough, causing this problem. I have 265/30/19's in the back so in hindsight, thinking that small of a sidewall would respond slowly is kinda ridiculous. But when you have problems, sometimes you grasp at straws.

Reminds me of a saying I once heard. If you hear hoofbeats, it's probably a horse, not a zebra. Car steers funny, who would have ever thought the front tires were to blame

The DWS-06 actually have a very good amount of grip, did not make the ride as good as I thought they would (I only bought 2 rears tho), and have made it much harder to drift my car. Overall, they have been as good as expected. It was these or AS3+ or Toyo Proxes 4+. I didn't want the harsher ride of the Michelins and barely anyone has tried the Toyos.

Last edited by Landshark92; 11-05-2019 at 06:35 PM..
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      11-06-2019, 08:52 AM   #15
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Quote:
Originally Posted by Landshark92 View Post
Draw a piece of paper with a diagonal line on it, pointing to the upper left. This represents the right tire with toe in. Now rotate that piece of paper 180 degrees and then place it in the position of the left front, the diagonal line still points to the upper left but since it is now on the left side, that would be toe out.
lol no, that's not how it works.

Again, unless you dismounted the tire to move it from right to left, the wear pattern will remain on the inside.

Agreed though, the Contis grip well and ride "ok" but suck at everything else.
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