December 22 2006   Story: Bryan Joslin

At some point or another, an older car is going to need some attention paid to its braking system, and our 15-year-old 318is is no exception. Considering the safety significance of the brakes, we decided it would be a good idea to go through that system thoroughly before doing anything to the car that would increase its power. Not that we're planning any power upgrades so potent as to render the standard braking system ineffective, but as they say, "Safety First!"

We planned from the outset to use our E30 as both a daily driver and an occasional autocross/trackday car, and all along we've been picking components that represented the best compromise between these two needs. With a car as lightweight as the E30, a "big brake" upgrade would simply be overkill. Most of the aftermarket race-type calipers found on these kits also tend to become unreliable once they've gone through a salty Midwestern winter. On top of that, their larger diameters necessitate larger wheels than are ideal for mounting winter rubber. As nice as big red calipers and large rotors look through the spokes, we opted to stay with stock caliper and rotor dimensions for now, and instead upgrade the specifications of the actual components. Since the braking system had no major flaws (i.e., seized, leaking or dragging calipers), we went ahead and ordered just new rotors and pads for each corner, as well as new brake lines and fluid.

For the new pads we turned again to the guys at BMP Design, who suggested PBR metallic pads. Although they are made from a slightly aggressive street compound, they bed in quickly and work well at low temperatures. They're an upgrade over PBR's non-metallic Deluxe compound, which would be sufficient for mild street use only. The PBR metallics will take us through Chicago's chilly winter and spring months, but we'll likely swap them out for a more aggressive compound once autocross season rolls around.

Rotors were a slightly more difficult decision. While it's true that standard solid-face rotors would have done just fine for street and autocross, past experience lead us to choose a more aggressive rotor for track day use. Under repeated heavy braking, a layer of hot gas will build up between the pads and the rotors, rendering the brakes less effective. This is what's referred to as "brake fade" and on the track it can be dangerous. The heat buildup eventually passes from the rotor to the caliper, where it is absorbed by the brake fluid, which can literally boil within the lines, leading to a soft pedal and longer stopping distances.

The best way to alleviate brake fade is to "vent" the face of the rotor, giving that thin layer of gas a place to go. The two common venting methods are slotting, which involves cutting a shallow groove in the face of the rotor, or cross-drilling, where holes are drilled through the face of the rotor for gas evacuation. Slotting is generally considered the less aggressive of the two in terms of pad wear and noise. But Brembo offered us a set of their cross-drilled Sport Brakes, which will work fine for the street and even better on the track, even if they are just slightly noisier. The cadmium plating on the rotors offer better corrosion protection than the more common "bare" iron pieces that were already on the car, hopefully preventing them from siezing to the hubs or the wheels themselves.

Given the age of our car and our plans to work it hard, we thought it would be wise to change out our brake lines at the same time we performed the other brake work. Even when new, the factory-fitted rubber lines are more flexible than the stainless steel-coated Teflon hoses we replaced them with. Under heavy braking, the rubber hoses have a tendency to expand, reducing the hydraulic pressure that reaches the calipers. On an older car like ours, the rubber can be degraded from age, causing premature failure under extreme pressure. BMP sells a special version of StopTech's Teflon lines. Not only is the stainless steel sheathing covered with a vinyl layer to prevent chafing of nearby components, but BMP's version includes their exclusive Swivel-Pivot fitting to prevent binding when the lines are secured, and they are plated for long-term corrosion resistance.

While a typical pad-and-rotor replacement won't require any servicing of the hydraulic system, changing the lines means the system will have to be bled at the very least. Of course, if you're going to bleed the system, you may as well go ahead and flush it completely. Brake fluid is hygroscopic, meaning that it attracts water. Water not only causes corrosion inside calipers and master cylinders, it also boils at a much lower temperature and has different hydraulic properties. As the fluid absorbs more water over time, the less effective the brakes become. As a result, many manufacturers recommend flushing the brake fluid every two years or 30,000 miles as a matter of routine service.

Again, with our eyes on severe driving conditions, we chose a brake fluid that will withstand what we plan to throw at it. German brake manufacturer Ate (pronounced "AH-tuh") produces a very popular brake fluid for performance-oriented drivers. Produced in both blue and yellow colors to make full flushes more visibly obvious, their Super Racing Fluid meets DOT 4 standards and has a 536 deg F (280 deg C) boiling point. Having used this fluid with great success in the past, it seemed like a wise choice to continue with it. Besides, there was a fresh, unopened can already in the garage.

We started the work by positioning the car securely on four jack stands. With the wheels removed, we worked one corner at a time, carefully removing each caliper, caliper carrier, and brake rotor. We did not remove brake lines until all of the mechanical components had been passed a quick visual inspection. No sense bleeding the lines twice if a caliper was going to need replacement.

The new rotors were bolted into place next, followed by the caliper carriers at each corner. Brembo's drilled rotors have dirctionally drilled holes, so we had to take car to get them placed on the correct side of the car. The reason we partially reassembled as much as possible before removing brake lines was to minimize the length of time any one circuit would be open. Not because we were concerned about air or moisture entering the system, but because brake fluid will continue to weep from the hard lines on the car until they are reconnected, and we wanted to minimize the our exposure (and that of our garage floor) to the nasty substance.

So only once all of the rotors and caliper carriers had been reinstalled did we start replacing brake lines. On E30's with rear disc brakes, there are six flexible brake lines- one for each front caliper, one for each rear caliper, and a pair that travel over the differential. The lines at the calipers are easy to access, but the ones over the diff are a little more difficult to get tools on. Given the time constraints we were under, we opted to hold off on the two center lines and replace them when we swap out the diff for a limited-slip unit later. This will require another fluid flush, but will be much easier.

A critical step in securing the new brake lines is making sure they are aligned properly. With their rigid stainless sheathing, they have a tendency to be particular about which way they bend. One by one, we secured the non-swiveling ends to the calipers first, and then bolted the calipers back onto their carriers with the new pads inserted. Only once the calipers were secured in place we were able to connect the swiveling ends of the new hoses to the hard pipes on the car.

Once all four calipers were reconnected, we made a final check of all the lines and fittings to make sure everything was right. The next step was to bleed the system, removing not only the air bubbles that had most likely entered the system, but also the old fluid. We did this with a one-man, vacuum-type bleeding kit that eliminated the need for the old "pump-pump-pump-open-close" method.

Judging by what came out of the bleeder valves on our car, the fluid had not been serviced in a long time. Brake fluid is naturally translucent, but as it ages and takes on debris, it becomes darker and more cloudy. The fluid that came out of our brakes was the color of molasses. It was so opaque that even with an incandescent work light placed right behind it, no light shone through its clear container. As the calipers were bled, rust-colored fluid passed out of them. We drew fluid out until it ran clearly through the tube, indicating all the old fluid had been evacuated from each of the circuits. We felt lucky that none of the calipers were corroded so badly that they seized.

With all of the work buttoned up and a firm brake pedal once again, we hit a side street to break in all of the new friction surfaces. It took only a few stops for the new pads and rotors to "mate" and making meaningful stops. A couple high-speed (from about 60 mph down to around 20 mph) removed the remaining unevenness and grabiness. The pedal now felt more appropriate for a BMW; more like a precision instrument than a dull utensil. At a complete stop, the brake pedal no longer can be forced to drop to the floor, and the amount of dead travel in the pedal is nearly gone. Brake pedal feel is slightly better, but this change will probably be more noticeable on the track when things are a bit hotter. Now that the brakes have been properly addressed, we feel a bit more confident about adding power to our little coupe. Next time around we'll tackle intake, exhaust, and software upgrades and see if we can give the new brakes a real reason to work.