Bad shimmy around 45-50MPH front rotors replaced recently

[Chris V]

And yours is anything but the rotors

So conflicted agh.

No, my suggestion was that it was thrust arms. I had the exact same symptoms, as do many people with these cars, and the common fix solved it.

On thing about the thrust arms, however. They have to be tightened down when the car is resting on it's suspension, as they have to be tightened under load or they will go bad again quickly or cause more issues. It's not hard to do, just something to remember (the suspension cannot be drooping while the car is up on jack stands or a lift when tightening the bolts up)

[sirbevo]

No, my suggestion was that it was thrust arms. I had the exact same symptoms, as do many people with these cars, and the common fix solved it.

On thing about the thrust arms, however. They have to be tightened down when the car is resting on it's suspension, as they have to be tightened under load or they will go bad again quickly or cause more issues. It's not hard to do, just something to remember (the suspension cannot be drooping while the car is up on jack stands or a lift when tightening the bolts up)

Isn't there a mod with hot glue to help with the thrust arm wobble? Anyone watching this thread maybe done that mod and what were results?

[Xproplayer]

No, my suggestion was that it was thrust arms. I had the exact same symptoms, as do many people with these cars, and the common fix solved it.

On thing about the thrust arms, however. They have to be tightened down when the car is resting on it's suspension, as they have to be tightened under load or they will go bad again quickly or cause more issues. It's not hard to do, just something to remember (the suspension cannot be drooping while the car is up on jack stands or a lift when tightening the bolts up)

My mistake, this issue has me scattered. I'll try to find a guide soon, if you have any recommendations please let me know

[racer2086]

It does sound like your thrust arms with the shimmy while driving and getting worse when braking. The hot glue method is a temp fix at best.

It is surprisingly easy to replace the arms with the right tools. It is two nuts and a ball joint tool to remove. As stated, they MUST be torqued down at the bushing end with the car's suspension loaded at ride height.

It is highly advisable to get an alignment after.

[Xproplayer]

I'll be honest, reading some of the guides and watching guides on how to replace this and I think it might be out of my comfortable level, anyone ideas on how much the control arm / thrust arms / traction arms (so many names) cost at a good shop?

[Aitch]

Buy the parts yourself and then take them to a shop to be installed. Meyle HD are usually recommended as not too expensive good options; I bought Moog which have been good so far. I think my install cost about $350 plus an alignment afterwards.

[racer2086]

If the shop will let you supply the parts, buy the arms from FCPEuro with the lifetime warranty. I had Meyle HD before and swapped to Lemforder. I think the Meyle HD bushing is good and HD, but the ball joints aren't as good as Lemforder. The Lemforder bushing is softer, but also reduces the transfer of the bumps to the car. Noticed that immediately. So a plus on that.

[shenofjo]

Aitch, reading your post reminded me of my situation as well. My road force balancing took care of the remaining shimmy. I still do get inconsistent slight vibration on the steering wheel occasionally but I am attributing that to road surface and maybe flat spotting of these sumitomos. Comparatively, these e38s have a lot more road feel going through the steering wheel than my Supra that gave no movement through the same surfaces.

[Xproplayer]

Boy for anyone who's been sticking with me this whole time you are a saint. Thanks a ton!

Anyways I'm torn now between the rotors and control arms, I'm actually leaning back towards the rotors again due to this timeline:

~Late September Starting to get a pulsing when slowing down the last 10mph at a stoplight, drove ~700 miles and noticed a violent shimmy when braking. I guessed that it was the rotors given the pulsing and again, happening during braking. Had the FRONT ONLY rotors replaced a what I figured was a trusted store, got non oem was quoted $400 for non oem and $600 for oem
October-Late November Unemployed wasn't driving much.
Late november picked up a job and started commuting ~12 miles each way to work, mixture of highway and surface streets but given traffic it was all over the place, did that job for about 2 months and then this post came in. My logic here is that the non oem rotors were good until they got warped after a month or two of driving.
About a week after this post lost said job and was unemployed from end of january until mid may when I got a job and have been commuting, which led me to start investigating the issue again.

Anyways I think I have both issues, arms and rotors given that I've almost always had a shimmy right around 50mph, the difference in the last ~8 months has been when braking and is far more severe than anything I've dealt with.

So right now it feels like the braking from about ~40-10 mph is a bit off, but below 10 is alright, maybe its me wanting to believe thats the issue since rotors are more diagnose-able.

Anyways I'm going to probably do the rotors are they are DIYable more than the struts and the cheaper option so which of these sounds like the best move.

Replace the rear rotors (still factory)
Swap front and rear rotors (incase the back are still good, might make the shimmy a bit better)
Replace the front rotors

Again thank you to the folks keeping up with me, I'm a freak with my car I simply hate not knowing what an issue is and I hate spending money on something that might not fix the issue (Spent $200 on a transmission fluid change that was shit and had to spend another $400 to get it done right, and now again with these rotors spending $400 on possible junk)

[ebida3]

Thurst arm bushings. Replace the arms. Very very common.

Check engine light (CEL) means 'Cost Estimate Large'

[Xproplayer]

Thurst arm bushings. Replace the arms. Very very common.

Check engine light (CEL) means 'Cost Estimate Large'

(B)ring(M)y(W)allet

But my shimmy doubles or triples in intensity while braking, you'd still point to the arms for that?

[ebida3]

Absolutely. As the weight adds pressure on the bushings they really squeeze down. Classic symptoms. I had the same exact problem as well as 85% of the folks here.

Check engine light (CEL) means 'Cost Estimate Large'

[racer2086]

You cannot swap rotors front to rear. They are different.

Besides that, I would recommend you just replace the fronts. You will not feel the rears like you will the fronts, and the rears are OEM.

(B)ring(M)y(W)allet

But my shimmy doubles or triples in intensity while braking, you'd still point to the arms for that?

Absolutely. Bad arms will magnify a rotor problem. Although, when I replaced my arms without doing the rotors, the shake was still violent, just...different. So you will know with new arms if you still need rotors.

I think for simplicity's sake, you should replace the front rotors and front thrust arms. It may cost you a little more, but it will make sure you start fresh.

My guess is that you have a combination of issues with both the rotors and arms. Even if the arms were ok, the violent shaking that's been going on has introduced undue wear on them, which has probably either made them bad or shortened the life.

Additionally, since you will have to do an alignment anyway, if you have the financial means, I would also replace the lower arms if they are the same age/mileage. Additionally, take the time to jack up the wheel and feel for play at 3 and 9 o'clock to make sure you don't have tie rod/centerlink problems. Take care of everything at once for 2 reasons: 1) to not pay twice for an alignment and 2) because worn suspension pieces may keep things from feeling perfect and wear other pieces out a little quicker otherwise

[ebida3]

Xproplayer is correct. Violent shaking upon braking are fr. rotors. The rear rotors if severe enough gives you a shake that seems as if it is under the seat not in the steering wheel.
But VIOLENT is a great descriptor.

Check engine light (CEL) means 'Cost Estimate Large'

[oldroller]

"Violent shaking upon braking are fr. rotors."

On a car equipped with A-arms, or American designed strut supports, yes.

But on the E38? Not when accompanied by a shimmy while driving at speed without brake application. A brake caliper dragging might be a possibility, but other symptoms would be experienced also.

The thrust arm bushings are a very soft bonded composition, which gives these cars their distinctive "drive". When they begin to get weak, the bond softens and the arm begins to oscillate within the shell from
suspension and road load. Apply the brakes, and you have a 'rubber bandy' oscillation that gets progressive as the vehicle load against the brakes becomes heavier.

To quickly paraphrase, you had a vibration and replaced rotors. You still have a vibration, it's time to replace the thrust arms.

Just a brake note - purchased a full set of 4 rotors drilled/slotted, ceramic pads and pad sensors from brakemotive76 on the E site, $200 total.
They have been perfect in 5K miles. If you're bound up to do the rotors anyway.....

[Xproplayer]

"Violent shaking upon braking are fr. rotors."

On a car equipped with A-arms, or American designed strut supports, yes.

But on the E38? Not when accompanied by a shimmy while driving at speed without brake application. A brake caliper dragging might be a possibility, but other symptoms would be experienced also.

The thrust arm bushings are a very soft bonded composition, which gives these cars their distinctive "drive". When they begin to get weak, the bond softens and the arm begins to oscillate within the shell from
suspension and road load. Apply the brakes, and you have a 'rubber bandy' oscillation that gets progressive as the vehicle load against the brakes becomes heavier.

To quickly paraphrase, you had a vibration and replaced rotors. You still have a vibration, it's time to replace the thrust arms.

Just a brake note - purchased a full set of 4 rotors drilled/slotted, ceramic pads and pad sensors from brakemotive76 on the E site, $200 total.
They have been perfect in 5K miles. If you're bound up to do the rotors anyway.....

My issue after replacing the rotors didn't come up right away, it took 2 months of heavy driving. And I only replaced the front rotors with non OEM, rear are still factory. This makes me think the non oem rotors worked for a short time and then got warped and brought back the issue. I'm sure the arms also have issues but I am trying to fix this violent shimmy first as it's a higher priority.

[shanecarmaster1]

My issue after replacing the rotors didn't come up right away, it took 2 months of heavy driving. And I only replaced the front rotors with non OEM, rear are still factory. This makes me think the non oem rotors worked for a short time and then got warped and brought back the issue. I'm sure the arms also have issues but I am trying to fix this violent shimmy first as it's a higher priority.

Each and every time I got non-OEM rotors, they'd be okay for only a short time before they warped. OEMs never warp for me. Shaving non-OEM makes them even worse because they can't dissipate heat, even less than when they're new.

[ebida3]

Good gosh, don't complicate this. As I said we all have been through this. There are two kinds of people here. Those who have done them and those that will do them.
I know you want to help​ but we have experience.
I mean no I'll will and always welcome replies but this one is a lock.
To review, a violent shake up front transmitting to the steering.wheel upon applying the brakes are ft. rotors. A 40-45 mph shimmy especially but not always set off by a bump and worstens with braking is the thrust arm bushings.
Of coarse you may have both but highly unlikely if the conditions started at the same time.

Check engine light (CEL) means 'Cost Estimate Large'

[ebida3]

I just meant that although your explanation is correct your statement, On a E38? confuses the issue to a inexperienced person.

Check engine light (CEL) means 'Cost Estimate Large'

[shenofjo]

Easiest thing is go get your rotors checked by the people that installed it 2 months ago for free. Say hey wtf check my parts! And if it's the brake rotors then do that, if not then do your arms.

[Xproplayer]

I'm going to buy some new OEM rotors online and install them myself, worst case scenario it doesn't fix it but I have peace of mind that these non oem won't go bad, then I can do the control arms myself or pay a shop.

[Xproplayer]

What suggestions are there for rotor brands?

I'm looking at lots of choices here.

https://www.oembimmerparts.com/1995-...rts-s/1927.htm
https://www.fcpeuro.com/BMW-parts/74...scend_by_price

[Chris V]

Ok, another thing in the mix: there is no such thing as warped rotors UNLESS you've tightened down the lug nuts incorrectly.

http://www.stoptech.com/technical-su...nd-other-myths

Read that carefully. It's from a reputable racing brake manufacturer.

http://www.brakeandfrontend.com/warped-rotors-myth/


Now that I've added that, the E38 thrust arms are a KNOWN WEAK SPOT that CAUSES A ~50MPH SHIMMY. Period. Especially while slowing or braking. As was mentioned, there are two kinds of E38 owners: those that have done this repair, and those that will. When you DO do this repair, do NOT get the cheap Chinese junk that will wear out instantly. Get OEM, and if possible, get the 750iL arms as the bushings are heavier duty and will last a lot longer in the 740.

[drinkingsnake]

I process to replace my thrust arm, with Lemforder unit , but i did'nt know the tips for the swap of the 750 one's.

Thanks for sharing

But , what i found by myself is , that's it's possible tightening the thrustarm nuts or ball joint nut, WITHOUT wheigted the car at all....;-)

( you just have to mesure carrefully the distance between the bottom of the rotor and the inner side of the fender ,just above the top of struts, when the car is on the ground , with the wheel in place,
Then you jack up the car, place it on the jackstand, remove the wheel, and with a roll jack, move up the bottom of the rotor ,until you get the same mesure as before, between strut top and rotor bottom....

Here you are , you could tight all nuts of the front end, as the geometry is the same , as if the car where on her wheels...)

regards,

Chris from France

[drinkingsnake]

" OFF Topic mode" :
Shanecarmaster1,
I'm really keen on your E38 Preface lift, and did you create a thread on hit ? any more Pics?

Regards,
Chris from france