Beware M5 owners / hub swapped running Zimmerman Euro Two Piece Rotors

[auaq]

I changed my pads and rotors last year around back in August or later. I went with the Euro two piece or floating type rotors for the fronts and similarly floating rotors in the rear (the same as the M3's). I went with genuine BMW pads too. Ever since I installed them I've noticed getting occasional vibrations coming from the front brakes. Sometimes I get smooth braking but otherwise not. The car was still drivable back then, but not anymore lately. The vibrations have gotten a lot lot worse. It's not just the typical steering wheel vibration or chassis vibrations that you often hear on the forum and is then advised to either R&R your thrust arm bushings or replace the tires or even replace the brakes, etc. The entire car is shaking violently between 40 to 50 mph regardless if I'm giving more gas or applying the brakes. Imagine driving over a rocky terrain at high speeds and everything is just falling apart. It is just unbearable to drive the car. I'm having to keep the speeds under 40mph and taking frequent breaks from driving and letting the rotors cool down. It seems that due to the construction of these rotors they are not particularly friendly for everyday use. I did some search and found a post on M5board that gives a little more insight. According to Dave Zeckhausen,

The Euro floating rotor is a pretty neat design. It's a mass produced floating rotor that is several pounds lighter than the American rotor.

First, the iron rotor is placed on a horizontal mold and steel pins are inserted into it from the middle. These pins have anti-seize paste on the ends that stick into the rotor and the other ends all face toward the center. Molten aluminum is poured into the mold at the rotor center and traps the inner ends of the steel pins. When the aluminum cools, the entire assembly is pulled out and, voila! You have a floating rotor!

These rotors are not perfect. Occasionally a slide pin can become seized. When that happens, the radial growth of the rotor is constrained on one side and there may be distortion and resulting shimmy. The stress can also cause the aluminum rotor hat to crack. This would not be detected in the United States until the rotor disintegrated.

These rotors will run hotter than the American rotors since they have less mass. So it's even more important to use high temperature brake fluid and decent track pads. The wheel bearings will be cooler, however, because the aluminum hat is isolated from the iron rotor and the only heat conducting path is the 12 steel pins between the hat and the rotor.

To give one an idea what's happening with my car is like having a really bad 'warped' rotor. The shaking intensifies as I get up to 40mph and above, and it subdues when I slow down. The pads are dragging along the rotor's surface (I can even feel the resistance when coming to a stop) and the brakes are getting pretty hot. The rotor's are already turning blueish and I can definitely feel the intense heat wave coming from them upon closer inspection.

I have already ordered a set of US style cheap rotors from ebay and will replace them pretty soon. I drive my M5 pretty much daily to work and anywhere else, and because of that I don't think these are suitable for me. They will probably work fine in short distance driving or maybe at track events with proper track pads and fluids, but definitely not for street driving. The only reason I got these rotors was because I wanted to try them out and feel the difference they make, but now I would highly suggest anyone to stick with either stock US one piece cast rotors or better brands such as Brembo's or Stoptechs as such if you do a lot of driving.

I do intend to inspect the pins closer and maybe even put it on our lathe machine at work to see if it wobbles while spinning or perhaps the hat is cracked. Will post pics when I get a chance.

[HoZy]

So instead of inspecting your own vehicle, you put a post online warning others about something you're not even sure about?

Did I read that correctly?

Cheers
Mat

[auaq]

I did inspect it with the wheel off but didn't had the tools at the time to remove the rotors off and inspect it furthermore. It would spin fine and didn't make any abnormal noises. Only when driven does the problem occur, so it was hard to tell what's actually wrong with it. Either ways ever since day one after installing them the brakes didn't feel right.

[ross1]

If you have heated the rotors enough to blue them then you are either badly abusing them, have dragging calipers or a seriously mismatched combination of pads/rotors driven hard.
I don't see anything to complain about.
Do you stop really hard and then leave your foot planted on the brake pedal?

[auaq]

No, I have never abused the brakes. The last set this car had lasted a long time and had no issues with them at all. The pads had only worn down and it was time to refresh both pads and rotors.

[auaq]

Also, to your last question. No, I do not brake hard, come to a stop, and leave my foot on the pedal for a long period of time. As I've said in the first post, braking is usually smooth even when coming to a complete stop. It's only occasional moments when I'm having these vibrations whether I'm applying the brakes gently or severely, or even when giving gas.

[JimLev]

Auaq, are your caliper pistons sticking?

[auaq]

I hope not, but I don't think so.

[BimmrMeUpSnotty]

That's what it sounds like is happening. Calipers are sticking, maybe the brake lines are all kaput?

[auaq]

I haven't really thought about sticky calipers considering the fact that the brakes usually feel fine and strong, and it doesn't pull to one side or anything like that. Although the car has 205k miles on them and both calipers and the lines and pretty much every part of the braking system are all original though. Also, when I removed the last set of pads this car had they had uniform wear on both inner and outer pads on both front axles. Similar findings for the rears. During brake R&R I usually clean up everything and lube up the sliding pins and even apply a light coat of lube on the caliper bracket where the pads ears rest on.

[BimmrMeUpSnotty]

Stock brake lines? Look them over real well for dry rot. I'd rebuild the calipers, and swap out the lines.

[computiNATEor]

Stock brake lines? Look them over real well for dry rot. I'd rebuild the calipers, and swap out the lines.

+1. Sounds like your guide pins and rubber slide-thingys need to be redone.

[JimLev]

Peel back the rubber boots when the pistons are out at least 1/2 way to see if they have any rust on them.
How many times has the brake fluid been changed?

[BimmrMeUpSnotty]

That's right, if the fluids have not been replaced, should be every 2 to 3 years, enough water builds up in there, lovely how brake fluid sucks moisture out of the air, the piston will be rusty. Hell, when I have a half a bottle of brake fluid in the shop, afyer 6 months, I toss it. Anyway, pockets of water build up in the lines, water compresses, brake fluid does not, sticky calipers result.

[Jason5driver]

Was this ever fixed ?

[StephenVA]

I converted my M5 2 years ago without any of theses issues. The entire Euro production has these brakes. Any competent shop should has resolved this guys issues many months ago.