Normal brake system maintenance for a BMW, or any other car, should include a yearly fluid flush and inspection of the pads and rotors. But when you subject your car to more extreme conditions by driving more aggressively than the average person or taking the car to autocrosses or track events, you will need to take a more active role in system maintenance.

First, you must select a good brake fluid. Generic or even most name-brand fluids you find at the local autoparts store will not withstand the increased heat of heavy brake use. The most important indicator of fluid quality is dry boiling point (over 500°F should be used for heavy street use, we use over 600°F fluid for racing). Brake fluid that has been opened does not have a long shelf life before it begins to absorb water and lower its boiling point. Close the top securely and seal in a Ziploc bag, no more than 4 months is suggested, less time if it is for a track or race car that experiences extreme temperatures.

The next issue is flush intervals. Once a year you should flush the complete system. You can alternate between a blue fluid (Ate Super Blue) and yellow fluid (Ate TYP200) so you can tell when the flush is complete. A pressure bleeder is a helpful tool for this and makes it a one person job. Always start bleeding the system at the caliper furthest away from the master cylinder and work your way forward (usually RR, LR, RF, LF in a BMW). A complete system flush will require approximately one liter of fluid.
In addition to flushing the system, you should bleed the fluid held in the calipers periodically. The fluid in the calipers is subjected to the most heat and with frequent bleeding, you can eliminate deterioration of the boiling point. Bleeding this fluid will require approximately 4-5 pumps of the brake pedal if a pressure bleeder is not available. This should be done before each driver's school or autocross, several times during a race weekend, or whenever fade is experienced.

Extreme heat generated during hard use will cause the rubber seals in the brake calipers to deteriorate. The calipers should be rebuild every couple of years, based on visual inspection, on most cars used on the track several times a year. We rebuild racecar calipers twice a year or more frequently depending on race duration and frequency.

Don't forget about the clutch during all of this work. It pulls brake fluid from the same reservoir as the brakes, but is often ignored. Bleed your clutch system the same way you bleed the brakes, once a year should be enough.