The “must-have” budget e28 brake upgrade.

posted in: DIY | 0

The e28 is a great car, but if we have to be realistic – it’s a great car with no so great braking system.
Well, every rule got its own exceptions, but still it could be way better just with little effort and investment.
(This article is focused to all e28 owners, except those with m5s. Yeah, yeah we know you got stock bigger brakes and mOAr power)

So, what’s all about.
We’re talking for a complete brake upgrade sourced from e34. Everything. Brake booster and master braking pump, calipers, carriers, rotors and pads.
And we’re talking here about a bolt-on upgrade without any mods. Well almost.

I’ll start this entry with some numbers:


Front rotors : 
e28 : 284mm x 22mm vented
e34 : 302mm x 22mm vented

Rear rotors :  
e28 : 284mm x 10mm
e34 : 300mm x 10mm

Front calipers piston diameter :
e28 : 57 mm
e34 : 60 mm

Rear calipers piston diameter :
e28 : 36 mm
e34 : 38 mm


Master brake cylinder piston diameter(s) :
e28 : Single piston – 23,81mm
e34 : Dual piston – Front – 25,4mm ; Rear – 20.64mm

Brake booster (exept e28s with hidraulic boosters) :
e28 : single diaphragm
e34 : dual diaphragm (in most cases)

Now someone might ask why not dual piston front calipers, or why not bigger and thicker rotors.
The key is here the balance. Experiments might risk your life and also thicker brake rotors and huge front calipers are not always the best option.This build is one whole system that was designed by BMW to work on a newer and heavier model car, with bigger rims and tires and fortunately completely bolts to the older model. So if it could stop an e34, it will definitely handle an e28. Actually we’ve tested this build couple of times on a trackdays, before writing this and car brakes & feels way better.

We’re accepting the scenario where you already bought your brand new e34 rotors and pads and you sourced your e34 calipers and dual booster.
Changing all the rubber components on the calipers is a number-uno priority task,before installing them on your car. We’have them here & it’s an easy job.

Start with taking the pistons out using compressed air.
It feels the same, but it’s cheaper than poppin a Moët bottle.

Then, take off the o-ring out of the caliper.

Remove the guide bushes.

Now this is the right moment when you can quick respray the calipers in preferable color OR you might do it like us and send the calipers to a sandblast and powdercoating. Don’t forget to tap them with the old pistons and some old brake hoses, so no paint will penetrate in the caliper chamber. Tight the bolts and guide pins to the carriers, otherwise you should clean some threads afterwards.

When they’re done start reasembling them.

Remove all the old stuff.

Clean the o-ring ports and sandpaper the chambers if they’re rusty or “dark”. 2000 grid !

Soak the new o-ring into a brake fluid and install it.

Dip the new piston into braking fluid aswell.

Put the dust cover into the back end of the piston and slide it into the caliper channel. This is kinda tricky and might take few tries.

Help yourself with a small flat screwdriver to push it there. Be really careful not to damage it. No room for errors here.

Use your ratchet extension and 27mm socket and hammer the piston in. There is a special tool, but if you don’t have it – that works great.

The dust cover needs to sit even everywhere. If you think it’s rising somewhere or it doesn’t look quite right, use compressed air to take the piston out and repeat the procedure.

Install the new bleeders.

And the new guide pins boots.

Use some special guide pin lube.

Usually new guides aren’t included to the repair kit,so if yours looks good and you can’t notice any damages, sandpaper them (2000 grid again – left ).

Slide them in.

Everything is same and applies for the rear calipers too that’s why we’re not going to explain it all over again.
You are done and ready to get them installed on the car.

Now about the dual diaphragm booster.

Your single diaphragm booster probably works just fine, but dual diaphragm produce a higher level of brake assist also it gives extra braking even if the vacuum from the intake is low. Also it’s an opportunity to delete your hydro booster which might leak in the near future if already didn’t.

Bolt pattern of the e34 booster is exactly the same as the e28 one.
The fluid tank cap got different connector, but e28 cap fits the e34 tank so no need of any modification here.
Since most of the e34s are having the ABS system, the front opening of the master pump is just a bit larger. So you need an adapter (i believe i could be found in any hardware store or brake shop) to make this happen. Also the cubic shaped adapter that connects to the brake pedal need to be adjusted to the right length by using 17mm wrench.

This is how it looks when installed on an actual car. Good news are we kept this upgrade in mind while we was designing our m52 swap mounts, so it fits just perfectly with m50/2/4 even if your m52 is using the m50 manifold. 

After a weekend of work, you have fully revised braking system. Don’t forget to change your brake hoses , your braking fluid and bleed the system.
Hint – start with the most distanced from the master brake cylinder caliper and approach it by the following order : rear right, rear left, front right, front left.
Also you achieved :

  • bigger and better brakes, that would heat up slower than the stock setup
  • 70%/30% front/rear balance braking ratio
  • 12% increase of the brake pedal travel

Enjoy the upgrade and the look of the new rotors filling better the gap behind the rim ^_^

George. The break horsepower breaker.