I’ve had this 2008 BMW e85 Z4 M car since new. This car has the e46 M3 CSL brakes with drilled rotors from the factory. Somewhere around year 5 I switched the semi-metallic factory pads to ceramic to avoid dust. My background is ex flat rate dealer Ford tech. I’m out of the biz since ~ 1998.

At one point the car developed a pulsation while braking. I can recall if it was a pedal or steering pulsation or both. It got worse, was annoying - but rotors were like $400 each. Only options were BMW, Centric, or Zimmerman. Eventually around year 12 I bit the bullet & bought new rotors & ceramic pads to fix the issue (Centric brand - matched set). Price has come down a bit since then, but not much.

Issue was fixed 100% with new rotors / pads. Now, about 12,000 miles later - there is a STEERING pulsation only when braking. It feels like a pedal pulsation, but the steering wheel shakes if you brake at around 65mph. You can see it do back & forth if you take hands off the wheel. Not so much at lower speeds. It’s similar or the same as the pulsation problem before that was fixed by new pads / rotors.

I’ve investigated this pretty thoroughly & am familiar with common issues that can cause this. I’m very gentle with the brakes & don’t keep my foot on them any longer than necessary. I know conventional wisdom says brake deposits on rotors & older conventional wisdom says “warped rotors” cause this.

What I’ve done:

1. Multiple multiple “bedding” hard braking procedures in attempt to heat up brakes to remove pad deposits from rotors. All this does is make it feel worse while rotors are hot. I’ve done it until the rotors smoke.

2. Dropped the aluminum belly pan many times to check the FCABS/ control arm bushings. Bushings are factory - but no sign they are bad. These are M bushings - I don’t think FCABS are fluid filled. Tie rods / ball joints are tight. All bushings have no hospital sign of being torn or bad. Front end shakes down tight.

3. Car has had multiple sets of tires, rim repairs, and wheel balancing since new. Wheels are as straight / balanced as they can be where I live there’s tons of potholes. There is little to no steering wheel vibration driving, a little bit about like 80mph depending on roads. Wheels are as good as when rotors where replaced prior & problem was solved by new rotors / brakes. Although wheels aren’t 100% factory new perfect; replacing tires, having wheels repaired / straitened have not changed anything

4. Checked front rotor runout with dial indicator on hubs. Max runout is ~ 0.0015”. It’s hard to check on drilled rotors, the indicator wants to sink in every hole on the rotor face.

5. Hubs are normally tight as they should be. No excess wheel bearing slop. Rotors hats are clean & hub centers are scrubbed with a wire brush & antiseize applied every time wheels are off - as wheels love to not want to come off this car from the hub sticking to the wheel; despite doing this (all 4).

6. Removed front rotors & mounted them backwards on rear axle. Ran car ~ 30mph w/ rear wheels jacked up using the hub as an arbor & sanded both sides of rotors extensively with 80 grit paper. Washed rotors well with brake clean. Rotors were uniform bright silver all signs of previous braking appear gone to the eye. Sanded pads w/ 100 grit so they looked resurfaced as well.

7. Checked brake caliper slide pins they are not stripped - cleaned & lubed. Car is meticulously maintained & all fluids / filters changed every 2 years (oil 1 year).

8. Car has been washed many times & not driven for a week or so causing rust to form on rotor face. Not uncommon for car to sit in garage for a month & then driven daily for a month.

9. This car has M3 CSL 2 piece style rotors. I believe the hats are aluminum. They are filled & this is how the factory made the car in 2008. Car came factory with semi metallic pads & I have been using ceramic. I believe problem started sometime after ceramic pads were installed, but that was like 10 years ago & has had 2 sets of ceramics since so I don’t remember exactly.

It seems like much or all of the “shake” is in the steering wheel opposed to pedal pulsation. If you let go the wheel turns itself 20 degrees or so side to side when braking from about 65mph. I can’t recall if the shake was only in the steering wheel 2 years ago when I replaced the pads/rotors with a matched set - but it def fixed the issue. The rotors are about $600 & I can find no good reason to replace them again - I don’t want the problem to come back. The runout is in spec.

The pad deposit theory does not seem to apply here. Sanding the rotors aggressively maybe improved it 15%if at all. There seems to be some cars that just have this issue & throwing brakes & rotors fixed it & it just returns in a few months to a year.

I think only 3 companies make rotors for this car: BMW, Zimmerman, & Centric. I’m going to measure again more closely - but it seems rotor “warped” or runout lacks evidence here. I didn’t check the hubs - because the rotors bolt to the hub & their runout shows good. Something I’ve noticed is of the car sits & the rotors are wet the pads leave a mark on the rotor the shape of a pad. I noticed these pad “marks” are very hard to remove. You have to sand aggressively with a lot of force to remove a pad mark.

Back in the day we used to cut rotors on a lathe & it would fix this issue, occasionally just temporarily. BMW doesn’t rec machining rotors, it’s not rec to machine drilled rotors, & cutting 2 piece rotors was always dicey. However if I had access to a lathe or had someone who would do it; I would get it done.

People recommend ceramic pads because they’re cleaner, quieter, & don’t wear / groove rotors as much. However, they are “harder” & leave pad deposits embedded on rotors. If that’s what is going on here, they are next to impossible to remove without a lathe.

Out of curiosity I ordered a pair of Wagner Thermo Quiet semi-mets for $20 from Rock Auto. If there are indeed “pad deposits” causing thickness or friction variations - I would think this would cure it over time as it wears down the rotor. The pads & rotors can from Centric as a set & seemed heavy duty & OE quality. Before anyone says Centric is no good, remember the factory BMW rotors were replaced cuz of same issue. The back rotors are original & I didn’t check for runout & if anyone ever heard of back rotors causing a steering wheel shake - please let me know

This car is known for being harsch & stiff & you feel everything through the steering wheel. It seems like certain BMWs have this issue & it’s temporarily fixed by replacing pads & rotors - but it seems to come back. I had this issue with my Nissan Frontier & replaced pads & rotors & it’s been good for years.

If anyone has any experience or input - I’d love to here it.