Project E39 M5, Part 1: Stopping the Ultimate Driving Machine


Much like other RWD cars, the M5 uses a drum brake type set-up for the emergency brake. The shiny surface inside of the rotor is the friction surface for the shoes (e-brake pads). The rear M5 rotors are the same thickness as all the other M5s, but at 327mm they are significantly larger in diameter than the rest (only 298mm). 


When I first started working on cars in my teenage years I remember tackling my first drum brake job. Let me tell you, it was not easy! A caliper and disc set-up is straight forward, while a drum set-up will require patience and the desire to read an instruction manual in its entirety. Thankfully for us, the techs at Pure Performance are well versed mechanics and our monkey hands stayed far away from this part of the job. Here you can see just how complete the StopTech hardware kit we sourced from is. These kits are complete and you will be absolutely pleased. No last second trips to the auto parts store or dealer for missing components. 


Our rear brakes completely assembled with zero extra parts left over. Success!


As mentioned previously mentioned the StopTech brake lines and sensors are a PERFECT fit. They're the correct length and have all the necessary mounting provisions for a clean and factory look.


With our new brake components installed and all hardware double checked, it was time for the final step of bleeding the brakes. The BMW ABS/DSC system is pretty finicky and getting a thorough bleed of the system after major components are replaced, like calipers or brake lines, can be a challenge using traditional methods. According to the Bently Service Manual a BMW Service Tester must be used when bleeding the brakes. The BMW Service Tester cycles all the ABS/DSC solenoids while new brake fluid is forced into the system. Once again, the BMW Specialists at Pure Performance were prepared with all the specialized tools. This machine is used to pull fluid from all the calipers while the BMW Service Tester does its thing.


Making sure the brake fluid doesn't go dry is extremely important when bleeding brakes. If the reservoir goes dry and air is introduced to the system, then the entire process must be repeated. This container has a specialized end that attached to the brake fluid reservoir and keeps the reservoir full with fresh Motul RBF660 throughout the entire bleeding process.


After bleeding the brakes we took the car out for a test drive and once everything checked out it was time to properly bed the brakes. I like using a 60mph to 0mph method where I bring the car up to 60mpm and quickly slow down to 40mph, release the brake pedal, quickly slow down to 20, release the brake, and finally come to a complete stop. I repeat this about 3-4 times until I can smell the brakes. It is key to never leave your foot on the brake pedal for more than a couple seconds at a time. Locking up the brakes or coming to a complete stop and leaving your foot on the brake pedal during the bedding process can lead to uneven tranfer layer. Bringing the brake components up to temp gradually will ensure an even layer of transfer film on the rotor surface. Which is critical for judder free operation and maximum braking performance.  

With our entire brake refresh/upgrade complete it was time to hit the road to Bear Mountain again…though this time we would only be enjoying the scenic views since all the white stuff had melted away. Even with hotter ambient temperatures during our second evaluation, the brakes performed flawlessly. Not a single bit of brake vibration could be felt and most importantly we experienced minimal brake fade. Even on our way down the mountain! The stainless steel braided lines gave us a firm and sporty brake pedal feel, eliminating the vagueness we experienced with the stock rubber brake lines. We could not be happier with the quality, completeness and performance of the StopTech Sport Kit. We also attribute a good part of our fade-free evaluation to the addition of our brake duct system. 

If you're looking to get the most performance out of your stock brake components, the StopTech Sport Kit is hands down the way to go.




Pure Performance – The BMW Specialists 

Cryo Science


1 comment

  1. What are the part numbers and where did you source the:
    – brake ducts
    – pork chop with duct slot. Wheel well liner.

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