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

The large stock E39 brake rotors have a little over 21 pounds of material to each of them. All this mass, directional venting vanes and additional venting holes on the rotor hat area help manage the large amounts of heat created when stopping the M5. We proved during our initial evaluation that when it came to brake fade prevention the car had plenty of room for improvement. To help remedy the heat management issues we discovered, we sent our rotors and brake pads off to Cryo Science for their cryogenic treatment. Cryogenic treatment uses extremely low temperatures to correct what room-temperature metal casting introduces to metals.  When metal is formed at atmospheric temperature the molecules are disorganized and contain weak carbon particles called Austenite. What Cryogenic treatment does is  convert these disorganized molecules and weak carbon particles into highly organized molecules and very strong carbon particles called Martinsite. The end result is a metal that is up to 50% stronger and will run much cooler. This all translates to a rotor and pad that will last much longer!

These brake ducts are the reason why our front bumper assembly is off the car. We are going to be adding a brake ducting system using all factory BMW E39 parts…that were not originally on the M5! These parts are from a 540i that came with a different front bumper and lower bumper grill. The “t-bar” grill from the 540i had the openings for these ducts. The M5's M-Tech front bumper is by far the best looking front bumper of all the E39s, but its lower grill does not have provisions for the factory brake ducts.

This is the driver side front inner fender liner from a 540i. Notice the large rectangular opening on the left side. This opening is completely closed off on the M5 fender liners. Pure Performance helped us find the right parts we needed and ordered all the BMW factory parts for us. The Germans are very proud of their parts, so be prepared to pay a premium. Yes, I could've cut out the openings on the stock M5 fender liners, but I want to keep some level of “refinement” with this build. So hacking things up is not an option. The openings will help direct air from the brake ducts to the back of the front rotors.

After a little web research we found that you can modify the front M5 lower grill with a pair of “sink drains” to create the holes necessary to drive air into the brake ducts. Home Depot Racing!!! These grills can also be found with silver rings, but we like the clean look of the black sink drains.

We didn't actually go to Home Depot, because our web research led us to a forum vendor that goes by the name of Slimmbones who specializes in E39 aftermarket parts and had already modified grills in stock. These grills are made from brand new factory E39 M5 lower grills and also come with all the necessary mounting hardware.