My '00 E39 had the movit/Porsche 993 Twin Turbo brakes for a while. I liked them somewhat; however, the pedal was a little too long and spongy for my tastes.
Just prior to selling my car, I removed this system as the new owner wasn't willing to pay a premium for these upgraded brakes.
For various reasons, I ended up getting the car back. But in the interim, I sold the brake kit to a "01 E39 M5 owner.
Not satisfied with the OEM brakes, I embarked on a different solution. In order to preserve the factory hydraulic ratio (i.e. the ratio between the total area of the pistons in the master cylinder in relation to the total area of the pistons in the brake calipers), this time around, I opted to retain the OEM calipers.
It seems that it is difficult, if not impossible, to source a larger master cylinder which contains pistons large enough so that the hydraulic ratio between them and the 44 mm and 36 mm pistons in the Porsche calipers remains close to stock. I believe that it was this alteration to my factory hydraulic ratio is what was responsible for the change in pedal feel and modulation that occurred with the Porsche calipers.
In order to optimize the factory brakes within the confines of preserving the factory hydraulics, I ordered European front and rear rotors.
These rotors differ from their U.S.-spec. in the following ways: they are floating front and rear, and the rear rotors have directional vanes. (Note: the rear rotors have a different part no. left to right). They cost about $250 each. The only negative side effect to floating rotors is there propensity to squeak and "drag" slightly more than their fixed counterparts. This can be heard by the driver when driving slowly with the windows down in an area with homes or buildings where the echo effect is apparent.
To further optimize things, I had these rotors cyrogenically treated.
The most important thing I did was get rid of the OEM brake pads. Short of Mintex, I couldn't find any company that made a replacement pad for the E39 M5. Finally, I found Carbotech in Fort Lauderdale, Florida.
Carbotech has a compound to die for!!! Not only does their material bite like a race pad, but they are super street-friendly. In the past, I have installed quasi-race pads on the street, but in every case I was very disappointed how they worked in the real world. Unless the driver put decent temperature in the brakes (i.e. got them hot), they simply wouldn't bite when cold. This plateau effect is particularly disconcerting if the driver needs to make an emergency stop without having used the brakes just before (i.e. an extreme lack of cold brake bite). This is something that inspires no confidence in the braking ability of the car.
Carbotech doesn't have E39 M5 brake pads on the shelf. Therefore, I had to persuade them to allow me to send them a set of E39 M5 "donor " brake pads so that they can remove the OEM brake pad material and install their own recipe!
Other than the fact that this compound dirties the wheels quickly and has a tendency to squeak more than the OEM brake pads, their astonishing stopping power is more than worth the trade-off!!! These pads simply transform the brakes of the M5, and the entire car itself!
I finished the brakes by having Carbotech source for me a set of stainless steel brake lines (I believe the E39 M5's OEM brake lines are the same as those on the 1996 - 2000 E39 528/540). I think that these brake lines are made by a company called Goodrich.
Finally, I used DOT 3 Ford steet brake fluid. This is an old racer's trick. When looking at the can, you won't believe what the wet boiling point of this stuff is (it's on par with that of racing brake fluid!). It's only about $3-4 per can, and doesn't have the adverse side effect of quickly absorbing moisture like racing brake fluid (something about the hydroscopic effect, etc.). That's why racers are constantly bleeding their brakes.
Sorry for the long explanation, but I thought that everybody on the board would like to know the results of my expensive experiment/science project.
I can't wait to see how the 4,000 lbs copes on the track. Last time I was at the track, it was with the OEM brake system, and I was not terribly impressed. Hopefully, the stopping distances and proclivity to fade will both be reduced.
If anyone needs the part nos. for the European rotors, please let me know.
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