Had a big problem recently. At some point in the past, someone had stripped the thread off the bleed nipple on my passenger side rear drum brake cylinder. Instead of replacing the cylinder, they justed used a larger nipple and forced it into the cylinder. Of course, when i went to bleed the brakes, the cylinder casting cracked. Bingo! One useless brake system. BMW quoted $206 for a replacement. Luckily, good old Dad found someone who could do one for $60. At least it was better happening now than at the track.