Putting on the Brakes

Putting on the Brakes

The first time I had taken my fine, previously-owned Bavarian automobile out onto the track, I had badly overheated the brakes, despite much work to assure that I wouldn't. Just to be really "sure" I had a problem, I flushed the brake fluid once more and tried again at another track day. I discovered that if you press hard enough on the brake pedal, you really can touch metal!

Additionally, one of the problems I had discovered while buying the car was its tendency to rotate (but not "pull") to the left under threshold (almost at lockup) braking. This "feature" was very predictable and fairly slow, so it wasn't too tough to correct by steering a hair against the rotation. The first time it happened, barreling down into a very tight turn (3a at SIR), was still quite "exciting" when I suddenly found myself pointed at the dirt hillside about three feet off my port bow. I made a point of practicing threshold braking late at night on some abandoned streets, to make sure my reaction to the rotation was natural and quick.

Between these two problems, it was clear my search for automotive bliss was going to require a little more work on the brakes. While I was suspicious of the poor quality metallic pads I had used, I decided to be thorough.

I did some research online and found that the front calipers and rotors from the E30 325i were a bolt-on (meaning no wacky work necessary) enhancement. The 325i caliper is a larger caliper that will fit a vented, or two-layer, rotor. The venting increases the surface area of the rotor (allowing it to cool quicker).

A trip to Aurora Autowrecking netted me a working set of 325i calipers for $35 each.

While I was there I learned a nifty trick you can do with boxhead wrenches to increase leverage when loosening bolts. Essentially, if you are using the "closed" part of the wrench on a tough-to-move bolt or nut you can take a second wrench of similar size and hook its box end into the open end of the first wrench. This effectively doubles the leverage available.

When the new pads and rotors I had purchased online showed up, I put the new calipers on the car. They were an almost perfect fit – I had to bend the corner of the dust cover slightly to make room for the caliper. After my previous work, replacing the calipers was easy to do as it didn't involve any new skills.

For pads, I chose the PBR Metal Masters. They are an intermediate pad with mediocre cold performance and decent warm performance. They served my purpose because they were very cheap and I had decided to run really poor, low traction tires for the first year. Since the work that brakes do is limited by the absolute traction of tires, using tires with low traction reduces the need for a set of better pads. With the new brake system I was able to lock the front wheels up at will on the track, therefore the pads were sufficient for the car and tire set up. There are many better (and more expensive) kinds of brakes pads available for track driving.

The next track day I found that my problem with the brakes overheating was completely gone. The downside of new set up was that over all braking was somewhat reduced. Why? Because with the beefier brakes, the front wheels would now tend to lock up much more quickly than the rear wheels. This means that the rear tires were doing less work slowing the car. All things considered, however, it was a huge improvement.

Unfortunately the car still had a tendency to rotate to the right under threshold braking. Replacing the calipers narrowed the problem down. I was now almost positive the problem was with the drum brakes on the rear wheels. My guess was that I'd find the problem in the right rear drum – if the right rear tire wasn't doing any work this would explain why the car was rotating to the left.

Boy was I right.

I ordered new shoes (what drum brakes use for pads) and new drums (the rotor equivalent). The next weekend, I took the drums apart. I learned several things: first, don't mess with brake drums unless you have extra parts. They're full of little tiny springs and parts that have the tendency to zing past your ear into the grass and be impossible to find. Second, I learned that you shouldn't mess with both sets of drums at the same time. Keep one exposed and complete for reference. This way you can go back and forth to see just how things fit. Third, reassembling drum brakes requires three hands.

The last thing I learned was that whomever had worked on these drums before me (certainly not a BMW shop!) was a complete imbecile. Springs were clipped into the wrong holes, and most importantly, the right side drum was MISSING a small but crucial part. In other words, the right drum wasn't doing very much work. My guess regarding the root of my rotation problem was looking right! There was one more test: I took the car out and did some threshold braking – and I found that the problem was gone.

One small step towards the perfect track car!