[drhousedk]

Hi,

I've been experiencing some vibration after repeated braking for some time. The first time at highway speed it's not that bad, but if you brake again shortly after, you're gonna have a bad time.

I immediately thought discs, so this weekend I replaced my front discs for OE brake discs and OE brake pads. Genuine BMW. I ensured that the hubs where smooth as silk, but the issue persists.

I'm wondering if the E9x suffers from some known issues that I might need to check out? Tie rods and ball joints are all okay. Bushings seems fine, but I don't know if they suffer from "heat soak" as a known E9x issue?

Wheels just got new rubber all way around, and road force balanced. No difference. Alignment was done. All okay, except rear camber. That got dialed in. No difference.

There's no vibration in the brake pedal. I would expect there to be, if it was warped rotors.

[tlow98]

It's the lower control arms. They're fluid filled and it seems like yours are shot.

Typical symptom is vibration in the wheel, not in the pedal.

[drhousedk]

I hope so - I picked this kit up (see attachment) yesterday. M3 might have been the better road to take, but due to the severity, I had to make do with what was in stock.

I love living close to the biggest and best BMW parts dealership in Denmark (KOED). The owner actually drove there himself to open up the warehouse, making me able to pick this up after hours!

[drhousedk]

Nope, that wasn't it either. All 4 arms replaced, and torqued to specs with the suspension loaded.

If I hang out the window when braking, I can see the left front wheel going crazy when I brake. I don't know about the right one for good reasons.

I've checked my side mirrors, and the rears doesn't wobble under braking.

Everything is new in the front. Bilstein B12 Pro-kit with 5000 kms on it now, at the same time I fitted brand new OE top mounts. Stabilizer bar links were replaced at the same occation.

My next go-to would be the tires. Not sure if they can start to act up when they get heated up - but everything else has been replaced now.

There is no play in the steering what so ever - I double checked today, both loaded and unloaded. I checked the rolling resistance in the front wheels - no unevenness at all, and they don't bind. This tells me that the rotors are straight and the calipers aren't binding.

[feuer]

e9x doesn't suffer from brake vibrations when control arms are bad like with older 3-series chassis. I assume you have sticking calipers. Do vibrations continue shortly after you get your foot of the brake pedal? If yes then sticky caliper it is.

[drhousedk]

Originally Posted by feuer

e9x doesn't suffer from brake vibrations when control arms are bad like with older 3-series chassis. I assume you have sticking calipers. Do vibrations continue shortly after you get your foot of the brake pedal? If yes then sticky caliper it is.

That would require the discs to be "warped", with brake dust residue or whatever. It was the exact same thing before, on the old discs. None of the rims are getting more brake dusty than the other.

It stops instantly when I release the brake pedal.

The caliper pistons went in evenly and with very little resistance when I pushed them in.

None of the front rims are hotter than the other - not after braking, not after a simple cruise where I roll to and standstill. In the latter case, both rims are cold.

[feuer]

Originally Posted by drhousedk

That would require the discs to be "warped", with brake dust residue or whatever. It was the exact same thing before, on the old discs. None of the rims are getting more brake dusty than the other.

It stops instantly when I release the brake pedal.

The caliper pistons went in evenly and with very little resistance when I pushed them in.

None of the front rims are hotter than the other - not after braking, not after a simple cruise where I roll to and standstill. In the latter case, both rims are cold.

Instantly, instantly? Get them really, really hot and check if vibration stop instantly after you release the brake pedal.

[drhousedk]

Originally Posted by feuer

Instantly, instantly? Get them really, really hot and check if vibration stop instantly after you release the brake pedal.

Instantly. As soon as I let off. Wheels equally hot.

Captured this video today. Note that the wobble is only when I'm on the brake, not all the time. Not very conclusive, but shows that something is clearly wrong.

Wheels moves freely and evenly when off the ground , even when warm. No difference in rolling resistance, left-right.

[feuer]

Originally Posted by drhousedk

Instantly. As soon as I let off. Wheels equally hot.
Captured this video today. Note that the wobble is only when I'm on the brake, not all the time. Not very conclusive, but shows that something is clearly wrong.
Wheels moves freely and evenly when off the ground , even when warm. No difference in rolling resistance, left-right.

Well, you changed the rotors and problem persisted, you change the control arms and the problem persisted. wheels are nicely balanced. It stops when you let go off the brake pedal so is not a sticking calipers. How old are the struts and the strut mounts?

[drhousedk]

Originally Posted by feuer

Well, you changed the rotors and problem persisted, you change the control arms and the problem persisted. wheels are nicely balanced. It stops when you let go off the brake pedal so is not a sticking calipers. How old are the struts and the strut mounts?

Struts and strut mounts have around 3k miles on them. Bilstein B12 with Eibach Pro-kit and OE strut mounts.

And that's what gets me. None of it fixed it. There are no bushings left to replace, other than stabilizer (and they are rock solid). Stabilizer links are brand new as well.

[drhousedk]

Just for clarification - it only happens when I've been kind of hard under braking. In the video I've been trashing it beforehand. It doesn't occur on regular driving in the city or on the rural roads (50 mph). It's only in higher performance situations like a high-ish speed freeway/motorway drive where I need to brake because someone eg. suddenly decides to switch lanes in front of me.

I drive rather often on the autobahns, so cruising speeds of 100 mph+ isn't that rare, and if I have to brake from 100 mph to, like, 60 mph twice within a mile or so, I'm having a bad time.

It just occured to me that only the rear tires were replaced. Fronts are WY0715 Hankook Ventus S1 Evos (K107), 10k miles on them. No visual damage, evenly worn and plenty of thread left, and they were road force balanced about 3k miles ago.

The rims, though, are some crappy (sorry guys) Alufelgen SF-71 (Ocean Caribien here). They are beautiful and fit the E91 like nothing else, but the strength is questionable. Could it be a rim or tire that misbehaves when heated up?

[feuer]

Only thing that you have not replaced are the calipers. At this point either rebuild or replace. Don't be mad at yourself if turns out that they should have been the first on your list. Sometimes that is how things work out.

[drhousedk]

Originally Posted by feuer

Only thing that you have not replaced are the calipers. At this point either rebuild or replace. Don't be mad at yourself if turns out that they should have been the first on your list. Sometimes that is how things work out.

And the steering rack, also heard that suggestion. And the wheel bearings (?!)

With no heat in the rims after a regular drive, even rolling resistance which is identical on both sides and no extra dust residue on either rim, I don't get why it would be a stuck caliper. :-/ They provided even resistance when I "retracted" (sorry, missing the correct word here) the pistons when doing the rotors and pads.

But, I'll see if I can fetch a rebuild kit tomorrow, for both calipers.

[Will_460cs]

I'd go with callipers and check the sliding pins first makes sure they are clean... To me it looks like brake issue with that wheel judder

I'd also re check the torque on everything...

I doubt it will be wheel bearings...

If that fails I'd check and probably disable ABS on the car and check and see if it still happens as this is the only thing that could be pulsing the brakes.

[drhousedk]

Originally Posted by Will_460cs

I'd go with callipers and check the sliding pins first makes sure they are clean... To me it looks like brake issue with that wheel judder

I'd also re check the torque on everything...

I doubt it will be wheel bearings...

If that fails I'd check and probably disable ABS on the car and check and see if it still happens as this is the only thing that could be pulsing the brakes.

Check the video. The wheel is wobbling like a mad. Sliding pins are brand New as well. Everything torqued to spec and double checked.

Was the exact same thing on the old brakes. NO difference. The hubs were cleaned spotless. No grinding, only wire brush.

[Will_460cs]

Originally Posted by drhousedk

Check the video. The wheel is wobbling like a mad. Sliding pins are brand New as well. Everything torqued to spec and double checked.

Was the exact same thing on the old brakes. NO difference. The hubs were cleaned spotless. No grinding, only wire brush.

could your ABS be activating?

[juld0zer]

Does your car have active steering?

[drhousedk]

Originally Posted by Will_460cs

could your ABS be activating?

No - it's not the ABS activating. It happens on even the lightest of braking when it happens, and the ABS has a very distinctive way of activating.

Originally Posted by juld0zer

Does your car have active steering?

No, it's got good old fashioned hydraulic assisted steering

[Will_460cs]

Well thats a difficult one for sure..! I'd try and get it to a Test station that has brake wheel rollers and test it there ...

[Needbmwpartzz]

Check steering shaft linkage...it can introduce some vibrations through steering wheel.

[juld0zer]

Originally Posted by drhousedk

No - it's not the ABS activating. It happens on even the lightest of braking when it happens, and the ABS has a very distinctive way of activating.



No, it's got good old fashioned hydraulic assisted steering

Apologies, i meant Active Steering as in the optional feature. ie. at low speeds does it turn lock to lock extremely quickly versus a normal car? Only reason i ask is that Active Steering models can actually steer the front wheels to help stabilise the car during DSC intervention in addition to pulsing the brake(s).

After watching both videos i am led to believe whatever is causing it has direct control of your steering. There shouldn't be any slop in the steering or suspension components that would cause that much movement or else it would be bloody obvious.

What happens when you turn around a bend and apply the brakes after you've thrashed them to get them hot enough to produce the problem in a straight line? Test this on a nice wide turn with minimal traffic!

[juld0zer]

Have you had the car scanned on a system capable of communicating with all the control units? ie something dealer level? I'd also recommend a full machine bleed + DSC bleed (activate the pump and valves), recalibrate both the acceleration sensors (the yaw sensor and the one inbuilt in the DSC control unit) and recalibrate the DSC valves and reset the steering sensor while you're there. Should take less than an hour.