1984 BMW E30 Front vs Rear Brakes: What Wears First and What to Replace

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 1984 BMW E30 the front brakes wear first, usually by a wide margin, because the front axle does most of the stopping work. What sits at the rear depends on which car you have: the 1984 318i with the M10 engine uses rear drum brakes with shoes, while the 325e uses rear disc brakes with pads. Identify your rear setup before you order anything, because the parts do not cross over.

Which 1984 E30 Do You Have: Rear Drums or Rear Discs?

The E30 3 Series arrived in the US for 1984 in two main versions, and they are braked differently at the back.

BMW's own parts listings bear this out: the genuine rear drum (228.5 mm) and the genuine rear brake shoe set are both catalogued for the 1984 and 1985 E30 318i with the M10 engine, while rear disc kits list the 325e and 325es from 1984 on. Later 318i and 318is cars (1991) moved to rear discs, so a parts book entry for "E30 318i" is not enough on its own. The fastest check is to look through the rear wheel: a flat disc with a caliper clamped to it means discs; a closed round drum means shoes inside.

At the front, every 1984 E30 uses a disc and caliper. The common pad shape for these cars is the one Hawk catalogues as the HB195 family, listed for the E30 318i, 325e, 325i and 325iX from 1984 through April 1991.

Why the Front Brakes Wear Out First

When you brake, the car's weight shifts forward. That loads the front tires so they can put more braking force into the road, and the brake system is proportioned to take advantage of it. The front pads and rotors end up converting most of the car's speed into heat, which is why they wear faster and why they are the first thing to look at on any E30 that squeals, pulls or pulses.

The rear brakes do a smaller share of the work and mostly keep the back of the car settled. On a healthy E30 it is normal to go through more than one set of front pads before the rear pads or shoes need attention. That changes if something is wrong: a rear caliper that sticks, a rear wheel cylinder that seeps fluid onto the shoes, or a parking brake left partly applied will wear the rear out early or make it drag.

Symptoms and How to Tell Front From Rear

• Brake pad warning light: the E30 uses wired pad wear sensors. A lit warning usually points to a worn front pad, but disc-rear cars also carry a rear sensor wire, so check both ends before you assume.
• Steering wheel shake under braking: this almost always comes from the front rotors, which have uneven thickness or pad deposits.
• Pedal pulsing without steering shake: more likely the rear. On a 318i an out-of-round drum does this; on a 325e a rear rotor with uneven thickness does.
• Grinding from one corner: pads or shoes worn to the backing. Stop driving and inspect, because metal-on-metal ruins the rotor or drum quickly.
• Parking brake handle pulls up high or will not hold on a hill: on disc-rear cars the separate parking brake shoes inside the rotor hat are worn or the cables need adjusting.
• Wet inner tire sidewall at the rear of a 318i: a leaking wheel cylinder inside the drum. The shoes will be contaminated and must be replaced along with the cylinder.

To inspect, pull each wheel. Front and rear pads can be checked for remaining friction material at the caliper; measure rotor thickness against the minimum stamped on the rotor or listed in the factory service manual. On a drum-rear 318i, the drum has to come off to see the shoe lining and the wheel cylinder.

What to Replace, End by End

Front brakes (all 1984 E30s)

Replace front brake pads as an axle set, and install a new wear sensor with them, since the sensor is designed to be consumed when the pad reaches its limit. If the rotors are below minimum thickness, grooved, or cause steering shake, fit new front brake rotors at the same time. Clean and lubricate the caliper slide points, and check the flexible hoses for cracking; on a car this age, replacing aged brake hoses is cheap insurance.

For a street E30 that also sees the occasional autocross, the Hawk HP+ front brake pads HB195N.640 for the 1984 to April 1991 E30 with HT-10 calipers are the performance option we carry. Hawk rates HP+ from 100 to 800 degrees F, with its best performance from 300 to 600 degrees F, and positions it for autocross and light track days. Expect more dust, noise and rotor wear than a pure street pad. If your E30 is a daily driver, a street compound is the better fit; Hawk's HPS line, for comparison, is rated 100 to 700 degrees F and described as gentle on rotors.

Rear brakes on a 1984 318i (drums)

Replace the rear brake shoes on both sides together, and install a new brake hardware kit (return springs and hold-downs), because tired springs let shoes drag or rattle. Inspect the drum for scoring and for wear past the maximum diameter marked on it. Peel back the wheel cylinder boots: any fluid means a new cylinder. Adjust the parking brake after the new shoes are in.

Rear brakes on a 1984 325e (discs)

Replace rear pads and rotors as an axle set along with the rear wear sensor. Inside each rear rotor hat is a small drum surface for a separate set of parking brake shoes. The OEM set for these is four shoes covering both sides. Because the rotor is off anyway, inspect those shoes whenever you do rear rotors.

Things to Do at the Same Time

• Flush the brake fluid. Fluid absorbs moisture over time, and a car that has sat for years usually has old fluid. Use the fluid type printed on the reservoir cap and bleed each corner.
• Check the hard lines and hoses. Decades-old brake lines can be rusty near the rear subframe; look before you put pressure through fresh parts.
• Look at the calipers. A seized slide or piston causes uneven pad wear. Replace a sticking unit with a rebuilt brake caliper rather than fitting new pads to a caliper that will wear them out again.
• Bed in the new pads. Follow the pad maker's bedding procedure so the pads lay an even transfer layer onto the rotors.

How Hard Is the Job?

Front pads and rotors on an E30 are an approachable driveway job with basic hand tools, a torque wrench and jack stands. The caliper comes off with a few bolts; tighten everything to the values in the factory service manual. Rear discs on a 325e add the parking brake shoe check and adjustment. Rear drums on a 318i take the most patience, since the springs, adjuster and wheel cylinder all have to go back in the right order. Take a phone photo of one side before you take it apart, and work one side at a time so the other stays as a reference.

Frequently Asked Questions

Does a 1984 BMW 318i have rear disc brakes?

No. The 1984 and 1985 E30 318i with the M10 engine uses 228.5 mm rear drums with shoes. The 325e from the same year has rear discs.

Do the same front pads fit the 318i and the 325e?

Yes. The HB195 front pad shape is listed for the E30 318i, 325e, 325i and 325iX from 1984 through April 1991. Confirm the caliper on your car matches the listing before you order.

How often should I replace rear brakes compared to the front?

There is no fixed ratio, but the rear normally lasts noticeably longer than the front. Inspect the rear every time you do front pads so a sticking caliper or leaking wheel cylinder does not go unnoticed.

Do I need new wear sensors with new pads?

Yes. The sensor is meant to wear through when the pad reaches its limit, so fit a new one with each pad change on any axle that has a sensor.

Why does my 325e parking brake not hold even with new rear pads?

The parking brake on disc-rear E30s uses its own shoes inside the rotor hat, separate from the pads. Worn parking brake shoes or slack cables cause a weak hold, and new pads do not fix that.

Is the Hawk HP+ pad good for a daily driver?

It works on the street, but it is built as a street and autocross crossover, with more dust, noise and rotor wear than a street pad. Pick it if you do autocross or track days; choose a street compound for daily commuting.

Sources

1. BimmerWorld - OEM rear brake drum 34211158556 - 228.5 mm rear drum on the 1984-1985 E30 318i
2. BimmerWorld - Genuine BMW rear brake shoe set 34219064270 - rear drum shoes for the 1984-1985 E30 318i M10
3. BimmerWorld - E30 rear disc brake package - rear discs on 325e/325es from 1984 and 318i/318is from 1991, rear sensor wire
4. BimmerWorld - E30 parking brake shoe set 34411159467 - four-shoe parking brake set for the E30
5. BimmerWorld - Hawk HP Plus HB195 front pads for E30 - front pad fitment and HP+ wear, dust and noise notes
6. Hawk Performance - HP+ compound - HP+ temperature range and intended use
7. Hawk Performance - HPS compound - HPS temperature range and rotor-friendly street use