Brakes

You can have all the power in the world, but at some point you're going to want to slow your E30 down. When it's time for some middle-pedal action, get to know what your brakes up are up to.

Overview

All E30s are fitted with a hydraulic braking system. When the pedal is pressed, fluid is pressurised by the Master cylinder to send fluid to each wheel. To help, extra pressure is generated by the servo, driven by the engine. This pressurised fluid powers the braking system, which on all E30s comprises of front discs and either rear discs or drums. A the front, the brake fluid will pressurise two calipers, which will squeeze pads against the discs to convert the kinetic energy of the rotating disc into heat. To a smaller degree, cylinders on the rear will press shoes against the inside face of the drums to achieve the same effect.

When you want the car to stay still, a cable-operated handbrake will lock the rear shoes in place. On cars fitted with rear discs, small handbrake shoes work on the inside of the rear disc.

Keeping all of the components fresh and leak free will help massively in preventing car/tree interactions.

Components

Brake Pedal

The brake pedal forms part of the pedal box, and it may surprise you to know that it is how the brakes are activated by the driver. It is connected to the master cylinder through a pull rod, which can be adjusted to control pedal height. There's a small rubber buffer on the lowest part of the bracket that holds the brake light switch, and the rod should be shortened until the arm of the pedal all but touches this buffer.

To adjust the brake pedal, slacken off the lock nuts and turn the pull rod using a 7mm open-ended spanner on the flats near the clutch pedal to adjust, until the brake pedal only has a small bit of upwards free movement to its stop. One end of this rod has a reverse thread, so turning it changes its length.

Be careful though. If you over-tighten things, so that the pedal is touching the buffer and moving the master cylinder push rod, the brakes are likely to lock on.

Brake Light Switch

The brake light switch is mounted to a frame just above the pedal arm, and is held in place with two small plastic tabs on its sides. It goes directly to the main loom, where it feeds the rear lights, and the Check Panel and Cruise Control if fitted. For cars fitted with a Check Panel, it is normal for the brake fault light to glow the moment the ignition is turned on; it will turn off the moment the brake pedal is pressed.

Brake Servo

The brake servo powers the master cylinder, making it easier on your braking foot. However, it does not improve braking performance; it simply takes the weight off your leg by replacing muscles with vacuum pressure.

It gets this extra pressure via hoses from the rubber boot on the engine intake system. Earlier cars used a very complex arrangement of hoses to supply pressure, for reasons unknown, while later systems were significantly simpler, using just one pipe from the throttle body to the servo.

When changing your engine or replacing your rubber boot, it is very common to find that you don't have the right number of holes to correctly connect your brake servo. Over the years, BMW tried all sorts of plumbing solutions to provide vacuum to the brake servo, and this resulted in a large variety of rubber boots on the market. If you find that your rubber boot doesn't have the right number of holes, simply connect all the other hoses to the brake servo in the most direct way possible, and plug any other holes.

For those attempting an M50 or M52 engine swap, a Renault Clio brake servo is a smaller alternative than the standard unit, requiring very little modification to fit.

Intake Valve

Because the brake servo receives air pressure from the Intake, it important for that pressure not to be lost. For that reason, a one-way valve is fitted in the hoses between the rubber boot and the brake servo. Occasionally this valve can fail, leading to loss of braking force.

ABS

Main article: ABS

Servicing

No brakes = no car. But you don't want to get into a position where you don't have any brakes, so preventative maintenance MUST be done regularly. The following parts should be inspected and replaced regularly

Upgrades

Main article: Brake Upgrades

The stock braking system fitted to the 325i and all Tourings is a perfectly capable braking system for the E30, no matter how aggressively you drive. However, if you're planning to race your E30, or you've changed your engine to something more powerful, it's worth looking at your options.

Remember, bigger doesn't always mean better; massive discs with 4- or 6-pot callipers will add a massive amount of weight to your vehicle, especially its suspension, and you may have difficulty finding wheels that fit. It's often enough just to fit racing-spec pads and discs, and keep your system in top performance with regular servicing.

Learn more about upgrading your brakes.