Front wheel violent shaking when braking on speed bumps.

[karlix]

Hello, it is my first time posting a thread here.


I bought a second handed BWM 520, about 46,000 miles so far.
It was owned by a very gentle old man,
and used this car for short distances only. Thus the condition was close to perfection.
Before I bought it, he made sure to check everything at the official BMW service center and everything was fine.


However, recently while I was going down hill into a underground parking lot,
I was going over some short but rough speed bumps, the front wheels were shaking like crazy.
It felt like it was going to fall off. The vibration was very very intense.

Once I released the breaks, the vibration was gone and i proceeded with the braking since I was still heading down.

I have went to long distances with this car, and I have had no issues in normal situations.
Even in high speeds, the brake was smooth and firm. But in low speeds and going over speed bumps, this shaking thing seems to occur time to time.


I have seen other threads discussing about the ABS kicking in, and saying that is is a normal response, but I wanted to get some more advice
from people who had similar experience.

It would be wonderful to get some advice.

Thanks.

[Plattus1000]

Tie rods. I think.

[jclausen]

Front thrust rod bushings

[morv]

I've got the same problem plus a bit of shaking when braking around 60mph. What am I supposed to change?
http://www.realoem.com/bmw/enUS/show...diagId=31_0617

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[TheAngryBear]

Tie rods. I think.

Front thrust rod bushings

And from my experience I was going to lean towards pads/rotors and pins.

As you can see, front wheel shaking may happen from a variety of issues. None of these are "wrong" but they aren't all going to be right either. You are going to have to test and/or diagnose.

I say rotors/pads and pins as that reflects my experience: initial application severe shaking/judders. Release and apply: all is good.

I can buy the others as it also presents the shaking/juddering. But I think those should also be present at other times (acceleration, cruise). All we know right now is that something on the front axle is "failing" under significant load (down a parking ramp). Hence the testing to narrow it down.


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[Ed CT]

Were you applying the brakes when the violent shaking happened? I think this is an ABS phenomenon that happens when going over a sharp bump or pot hole at slow speeds when the brakes are being applied. The ABS gets tricked into analyzing the temporary bump or dip as a lost traction situation, and reacts continually while the wheel is bouncing back from the bump or pot hole, and causes the wheel to keep bouncing, starting a temporary chain reaction of sorts.

This happened to me a couple of times, I did not do anything about it, it hasn't happened in a long time, and I actually forgot about it until I read your thread. My advice: don't worry about it, avoid the brakes while going over pot holes or speed bumps, and enjoy your nice E39.

[TheAngryBear]

Ed shows another case of what could be.

I made the assumption that you felt it in the steering wheel only and no associated pedal action, true?


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[DHoang]

However, recently while I was going down hill into a underground parking lot,
I was going over some short but rough speed bumps, the front wheels were shaking like crazy.

Not always, but It's most likely the THRUST ARM BUSHINGS, aka TENSION ROD BUSHING that's causing this.
The original thrust bushings are liquid filled. over time, the liquid leaked out, and the hollow air space
inbetween the bushings allows movement, which eventually leads to the bushing tearing and that's when
the violent shaking starts to surface. My thrust arm bushings gave out at 40k miles. I've had to replace them
every 50k miles. THis last time, I went with solid thrust arm bushings. Mine's at 40k miles now, and so far it's
still holding up.

The part(s) to replace is the #5 in the pic below:
http://www.realoem.com/bmw/enUS/show...diagId=31_0617

edit:
it's an easy job. One bolt to loosen, pop out the old bushing, pop in the new, and bolt it back in.
no alignment needed, nothing else to take off to service it. you should be in and out of a shop w/in an hr.
Bushings are $30-$40 USD each.

[gmak]

OP: Another point is that if the previous owner only drove the car short distances all the time, then (depending on the frequency of oil changes), there may be sludge build up - especially in the CCV. Look at the underside of the oil cap and see if there is a brown or mayonnaise build-up.

[ViolinARC]

Not always, but It's most likely the THRUST ARM BUSHINGS, aka TENSION ROD BUSHING that's causing this.
The original thrust bushings are liquid filled. over time, the liquid leaked out, and the hollow air space
inbetween the bushings allows movement, which eventually leads to the bushing tearing and that's when
the violent shaking starts to surface. My thrust arm bushings gave out at 40k miles. I've had to replace them
every 50k miles. THis last time, I went with solid thrust arm bushings. Mine's at 40k miles now, and so far it's
still holding up.

The part(s) to replace is the #5 in the pic below:
http://www.realoem.com/bmw/enUS/show...diagId=31_0617

edit:
it's an easy job. One bolt to loosen, pop out the old bushing, pop in the new, and bolt it back in.
no alignment needed, nothing else to take off to service it. you should be in and out of a shop w/in an hr.
Bushings are $30-$40 USD each.

This is highly likely, however, I would service the brakes first. Remove the calipers and check for leaks or failed seals, look at the rotors for uneven wear and for good measure, remove, clean and lube the slider pins. Replace and revisit the area where you are experiencing the issue. If the issue still persists, it's highly recommended to replace the TAB's and TA's fme...

I agree that TAB failure is one of those issues that can cause other things to crop up (especially NVH) but it isn't always the end all solution. For me, I experimented on the '00, which now has the Powerflex Black TAB's but there is still a slight but detectable vibration when cruising and definite brake-n-shake when hard braking down the mountain (braking system has been refreshed already due to attempting to solve the brake-n-shake issue).

For the '03, I followed the same procedure only to experience the same results sooooo I opted to spend a few more dollars, removed the powerflex and installed the G.A.S. (German Auto Solutions) Monoballs. IMO, it is the single BEST suspension upgrade so far because the ride is smooth as silk and there isn't even a hint of the annoying brake-n-shake!!

Good luck with your issue, it IS solvable...

[Wolfen]

Internet rumor. They were never liquid filled. The design has rubber tabs the break from the bushing and give space to wobble. Its considered a replacement item anywhere from 40-100K

[karlix]

Not always, but It's most likely the THRUST ARM BUSHINGS, aka TENSION ROD BUSHING that's causing this.

Thanks a lot.
I will check into the thrust arm bushings with my mechanic.

But in what kind of situation did you feel this vibration? Was it a similar situation as mine?
Also, what do you think about the ABS? Do you think the ABS could be the source of this problem?
I would like to hear your opinion

- - - Updated - - -

Were you applying the brakes when the violent shaking happened? I think this is an ABS phenomenon that happens when going over a sharp bump or pot hole at slow speeds when the brakes are being applied. The ABS gets tricked into analyzing the temporary bump or dip as a lost traction situation, and reacts continually while the wheel is bouncing back from the bump or pot hole, and causes the wheel to keep bouncing, starting a temporary chain reaction of sorts.

I was applying breaks during the down hill, and the shaking happened when I was pressing on the brakes.
When I released it after going over the speed bump, the shaking stopped.


Yes.. I think it can be an ABS problem, but I'm not sure if this is something I shouldn't be worrying about.
The car was already serviced at the BMW service center and everything was fine. I'm a bit confused at the moment.
I guess It won't hurt to bring it to a mechanic and re-check it for further issues...

[ViolinARC]

IMO, releasing the brakes and reapplying to "solve" the shaking can still be related to the thrust arms. The feedback starts on the first braking application and after you release and reapply, you've essentially reset the thrust arms by relieving the initial stress...

Neither of my 5'ers does this so it certainly isn't normal. Shame on the BMW dealership since obviously everything isn't "fine". These are incredible machines and should be solid when tracking any bumps in almost any situation (braking or not). I've been driving the '00 since 2007 (with 95k and now at 235k) and it took a while to track down the brake-n-shake issue but I will bet that something is awry. The '03 (with 72k) started acting up a couple thousand miles after I added it to the stable and I replaced the TAB's immediately. At 85k, I refreshed the suspension (including struts/shocks w/Koni Yellows) and revisited the thrust arm bushings again because of the shimmy and minor brake-n-shake...problem solved.

As stated, I had the awful brake-n-shake on both the '00 AND the '03 (much more violent on the '00). The thing that made the biggest difference was replacing the thrust arm bushings. Using the Powerflex Black definitely reduced the feedback on the '00 when braking but as I said, DIY'ing the G.A.S. Monoballs on the '03 have eliminated BOTH of these infamous issues...just my 2-cents. Good luck...

EDIT: Maybe you should have the mechanic do a ride along with you and take him to the place where the issue is most prominent. It should convince him that all is not "fine". I did that with my old E32 ('89 750iL) when the mechanic kept telling me that I was too "sensitive" and was just "feeling the road" until I drove through a very smooth section of freeway during a ride along and he agreed that there was a shimmy and brake-n-shake. I never had a chance to fix the issue because sadly, she was stolen and totaled shortly after that diagnosis...

[karlix]

These are incredible machines and should be solid when tracking any bumps in almost any situation (braking or not).

Thank you for your insight based on your experience. I really do appreciate it.
Yes, I fully agree that these are great machines that can withstand even harsher situations, and the response I am getting from this speed bump braking isn't normal.
I will visit my mechanic and discuss this issue in more detail.

Could you give me a link where I can buy the specific TAB that you are referring to?

[ViolinARC]

Sure...HERE ya go!

Mention that you are a Bf.c member and you might get a discount...

EDIT: WOW...the G.A.S. are a great deal in comparison! HERE is a link to the Dinan version. Notice what it says about braking...

[gmak]

Sure...HERE ya go!

Mention that you are a Bf.c member and you might get a discount...

EDIT: WOW...the G.A.S. are a great deal in comparison! HERE is a link to the Dinan version. Notice what it says about braking...

You mean "Reduces brake shimmy"? Brakes don't shimmy. What does that even mean?

[crazy4trains]

Were you applying the brakes when the violent shaking happened? I think this is an ABS phenomenon that happens when going over a sharp bump or pot hole at slow speeds when the brakes are being applied. The ABS gets tricked into analyzing the temporary bump or dip as a lost traction situation, and reacts continually while the wheel is bouncing back from the bump or pot hole, and causes the wheel to keep bouncing, starting a temporary chain reaction of sorts.

This happened to me a couple of times, I did not do anything about it, it hasn't happened in a long time, and I actually forgot about it until I read your thread. My advice: don't worry about it, avoid the brakes while going over pot holes or speed bumps, and enjoy your nice E39.

More than likely this is what's happening. The common term is "death wobble" and it occurs at lower speeds with brakes applied. Likely your front struts/shocks are worn out. Mine did the same thing and new struts solved the problem.

[DHoang]

Internet rumor. They were never liquid filled. The design has rubber tabs the break from the bushing and give space to wobble. Its considered a replacement item anywhere from 40-100K

I agree there's space to wobble, but the rubber itself has space for fluid.
my car was under warranty back in 2001 when i first brought my car into dealer for the dreaded shimmy.
I didn't know a thing about thrust arm bushings, let alone what it was called.
The BMW dealer back then showd me there was fluid leaking down on the bushings. so they replaced mine under warranty.
here's a pic of what it looks like w/ fluid leakage.

[Wolfen]

I have swapped many Arms and bushings. Im currently on Solid Busing Arms. I have never to date seen a Bushing with fluid. I just dont see it and never have. That pic could be anything. Mechanic could have sprayed wd 40 there. Other members also stated the same thing. We never saw a fluid filled bushing of any kind. Maybe i havent seen them all yet and theyre out there i just havent seen them .... ever.

[WBAD530i]

Brah thats cuz all yer fluid leaked out. How can you see what is not there to be seen?

I assume they have the same function as motor mounts. I definitely saw fluid in those. Unbolt those bad boys and raise/lower the motor and it will gush right out if they are old and failing.

I am having hard time understanding who is right and who is wrong, and what kind of lie all the e39 owners have been living with these thrust arms failing.

[ViolinARC]

Brah thats cuz all yer fluid leaked out. How can you see what is not there to be seen?

I assume they have the same function as motor mounts. I definitely saw fluid in those. Unbolt those bad boys and raise/lower the motor and it will gush right out if they are old and failing.

I am having hard time understanding who is right and who is wrong, and what kind of lie all the e39 owners have been living with these thrust arms failing.

NOT a rumor or lie...the TAB's fail on these cars causing TONS of NVH when cruising or braking! Ask me how I know. After my last DIY on the '03, ALL NVH has been SQUASHED by the upgrade to the monoballs! Nothing like real world experience to explain exactly what is going on. The original design (fluid filled or not) is FLAWED and when it fails, is the source of many complains about ride quality and handling due to deflection. That being said, after replacing these damn things more than once, the relief from NVH is only temporary and quickly returns (yes, I know how to preload properly). I finally became frustrated enough to try a more expensive option and without a doubt, feel I have found THE solution to many of the issues associated with the flawed TAB design. It was interesting to note that the solid Powerflex bushings made the thrust arm totally immobile while the monoballs allow the thrust arm to move freely in a side-to-side motion, which made me wary of their effectiveness. All concerns were eliminated after the first test drive though...sweet, smooth ride devoid of ANY NVH and that was on worn out tires.

FWIW, for me, this turned out to be the final solution to an ongoing point of contention for my beloved E39's. Now that I know how to solve the NVH, I'll never go back to the OEM TAB's or the solid bushings...just FME.

[ViolinARC]

You mean "Reduces brake shimmy"? Brakes don't shimmy. What does that even mean?

I didn't write it man, Dinan did! I call it "shaking" and was just providing a link to monoball kits for the OP.

Also notice that the Dinan site claims to be the only ones with "sealed bearings" but if you read the description on the G.A.S. site, their bearings are sealed too.