Fitting E34 Brakes

If you've dramatically increased your engine's power, either by an engine swap or Forced Induction, then you're going to need some bigger Brakes.

This guide walks you through fitting E34 front calipers together with an E32 servo and master cylinder. The standard E30 master cylinder is not big enough for the E34 calipers.

This is not a bolt-on process. Some fabrication and custom parts are required to fit everything together.

Parts

• E34 540i Front calipers, Carriers, bolts, clips
• Audi TT MK1 312x25mm vented front discs x2
• E34 540i Brake pads (your choice, I chose brembo OE)
• Caliper adapters
• M12x40 Nylock nut and bolts x8 (ebay)

Tools

• 13mm brake pipe spanner
• 17mm spanner
• Allen key set
• Hammer
• Jack and jack stands (or post-lift if you're a flash git)
• Some stiff wire
• Die
• Grinder with discs
• Drill and steel drill bits (up to 12mm)

Procedure

Preparation

Loosen the front wheel nuts on each side, then jack the car up using the appropriate Jacking Points and secure it on jack stands. Remove the wheels and place them under the car for safety.

Next crack off the brake hoses going into the front calipers. Undo the caliper carrier bolts (17mm), remove the entire caliper assembly from the disc, and rotate it multiple times to get the brake hose out.

Take the appropriate sized Allen key and undo the brake disc retaining bolt. With that off, the brake disc should wiggle off the hub. A few clouts with a hammer from behind can help.

You should now have a bare naked hub to attach your new brakes to.

Brake Discs

First on is the new brake discs. We're using 312mm discs from an Audi TT Mk1, and these will need some modification to fit. The centre bore needs opeing up 1mm and two holes need drilling in between the two current bolt holes

You can either give the discs to a machine shop to mod for you, or do it yourself using a drill and a Dremel.

To do this yourself, bolt the Audi 312mm disc to the BMW 260mm disc with the E30 wheel nuts so that the cone centers the discs. Use a carbide burr to open up the centre to match the BMW disc, then drill the required wheel bolt holes through the BMW disc and into the Audi disc. Start with a small drill bit before moving up to a 12mm bit.

Before you attach the disc, bolt the front bracket to the hub with two of the M12x40mm nuts and bolts

Attach the disc and bolt to the hub using the wheel nuts to stop it moving about while we fit the calipers.

Calipers

Scored the front brackets first all the way from germany

E34Brakes001

These were designed to be used with the above caliper and an audi 312mm disc Picture from google to compare the calipers E34Brakes002 (download new version)

Difference between stock e30 disc and audi one E34Brakes003

The brake carrier needs some slight grinding to line up the holes in the bracket and carrier, because it hits the hub. This will be trial and error on your part but I found it to be about 3-4mm (grind you carrier at your own risk)

Once the carrier is bolted in nice and tight you can install the pads with copper grease on the contact parts.

Wind the caliper onto the brake hose, then attach the caliper to the carrier with the two slide bolts (7mm allen)

Tighten the brake hose in caliper with your 13mm spanner

REPEAT THE OTHER SIDE and admire your new front brakes

Master Cylinder

With the E34 calipers on the front, and potentially bigger brakes on the rear as well, the standard E30 master cylinder isn't big enough to move enough fluid. To get around this, most people use the E32 750i MC but I also wanted more assistance to match. The 750i MC is also becoming increasingly expensive due to its rareity, so I'm opting to use a more mundane E32 735i MC and servo instead. This master cylinder is still 25mm, so should improve the feeling to near stock level

However, a few mods will be needed to make this fit.

The E32 I got mine from had a spacer on the back of the servo. There are two options here:

1. Use the spacer. This requires the least mods but the brake fluid reservior will be right underneath the inlet boot on the M20 engine, and might not fit.
2. Ditch the spacer, but make a few mods instead. This involves:

Grinding down and shortening the push rod to put the clevis at its original level Open up 2 holes in the bulkhead Bend the brake lines slightly

I choose number 2 for an original look to the engine bay

Start by opening up the mounting holes E34Brakes005

Grind down the pushrod E34Brakes006

Start making the thread using your die E34Brakes007

Cut about an inch and half cut off (37mm), and thread it as far as you dare E34Brakes008

Remember if you're doing this yourself then leave the die wound on before you cut the excess off. That way, you can then unwind it and clean the threads so that the clevis can go on with no trouble

test fit E34Brakes009

I was made up that the standard E32 vacuum line was in the perfect place to line up to the E30 system

The clevis is the trickiest part I lost the E30 clevis so I used the E32 one but it was way too long. This required trimming and slight mods so please keep your E30 one unless you want some trial and error fitment issues that involves installing and removing the servo/clevis multiple times E34Brakes010

All done apart from take it all apart to paint the servo and bench bleed the MC E34Brakes011