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Hi all

I'm looking at doing this upgrade on both the front and rear brakes in our car and was wondering if we have to replace the master cylinder with the E34 one as well? I've got the carriers and calipers but not a MC yet, I was planning on keeping the original MC and having it reconditioned.....

I've found various posts with some saying replace it and some saying it won't matter. Has anyone done this and kept the E24 MC? What was the difference in stopping?

Any advice is much appreciated.

Cheers
Mark

Don’t know about e34 mc: 750i is the usual recommendation.

I bought one but didn’t fit it as I was quite happy with the brake feel

The E24 master cylinder worked just fine for me when I did the 7 front/ 5 rear upgrade way back when. I did the E32 master when it was time to replace the original. The E32 made the brake pedal line up better with the throttle during heel/toe down shift.

Ross

Mark,
If you do the M/C upgrade use the e32 early 750, before 12/90, as the later one after 12/90 is incorrect.
It has the larger bore and will fit the e24.
And the 750 is less $ than the e24

I changed my front and rear calipers to the ones used on the E34 540 about 5 years ago but did not change the master cylinder. I think it was worth doing for the additional stopping power, and also under normal conditions, the pads last longer. The pedal feel didn't change, but if you really slam down on it you can stop very quickly, more so (and with less fade) than the originals. With the much larger vented discs all round you have much more cooling potential. I've not noticed any issues with retaining the original master cylinder.

On a side note:
I bleed my brakes once a year and using Castrol DOT4. I had stainless steel pistons made for my re-conditioned calipers and I used original BMW seals. They were painted with POR15 caliper paint and I installed Stahlbus bleeder valves and HEL flex lines.
Nick

On my 89, I went with M6 front and e34 rear. The MC is original and it's a big difference, brakes flushes every other year.
Will upgrade the MC to the e23 when the time comes.

Thanks, have ordered the E32 MC so will get that put on as part of the upgrade.

Finally pulled the calipers etc apart this week, all off to the powder coater now

I've received all the new rotors, bolts , pads etc. can't wait to get stuck into this!

Just had a thought though, before I start changing everything over, and knowing the E34 rotors are larger, is there enough room for the new rotors with the stock dust shields or do I need to modify them or use 540i dust shields?

Cheers
Mark

Hi Mark,

Let us know how it works out.

Where did you source the brakes & MC?

Cheers

Greg

Hi Greg

I found the rear calipers and carriers on a wrecked car here in Christchurch. That left the fronts. After an exhausting search on google and ringing just about every wrecker in NZ with no luck, I ended up biting the bullet and got the front calipers and carriers from Australia.

The easiest bit was the MC, ordered that new from the US.

They're now all rebuilt, painted up and ready to go onto the car (when I find the time).

Cheers
Mark

Rangi246 wrote: ↑Fri Apr 19, 2019 2:33 pm
Just had a thought though, before I start changing everything over, and knowing the E34 rotors are larger, is there enough room for the new rotors with the stock dust shields or do I need to modify them or use 540i dust shields?

Cheers
Mark

The dust shields do not need modifying, in fact nothing does! If you are rebuilding the calipers be sure to use genuine BMW (well, ATE) dust boots and square cut seals as these far superior to anything else I have seen. You may find the wires for the pad wear indicators are a little on the tight side but they will fit. I'm thinking about getting the wires from an E34 which are slightly longer.
Good luck.

So I finally got round to replacing the MC with the 750i one and putting the new discs and rebuilt calipers on with new pads.

They look great, however I can't help but think the brake pedal travel is just a little bit much. I bled the MC before installing it and have bled the brakes about 4 times all round (in the correct order). Absolutely no air is coming out anywhere so i'm wondering how long it takes for the brakes to bed in?

I've had the car out on the road up to 100km/h and stood on the pedal until the speed dropped to about 30km/hr, did this about 8 times to help the process. They seem to be getting better but I still think the pedal is travelling a little far. I'd say its going about 1/3 in before I feel any significant braking.

The only thing I haven't touched is the brake bomb, does this have any bearing on pedal travel?

Cheers

There shouldn't be much travel with that MC. Are you sure that it is fully bled? If you push the pedal 20 times, does it get rock hard, or does it still remain slightly squishy? If so, that would suggest air is still somewhere in the system.

Push 20 times with the engine off. With the engine running it won't discharge the pressure in the brake bomb and won't prove anything.

Finally got the brakes on the car sorted.

The booster was leaking at both ends and the rear calipers were retaining air for some reason.

A big shout out to Jay Stratton for his help with a new rebuilt booster. I tried to get several places here in NZ to get someone to look at it and they all turned me away saying that they only do vacuum based boosters. With Jay's instructions, the new booster is in, also did the brake bomb seeing as everything was out of the car, re-bled the brakes a few times and now the brakes are spectacular.

Thanks Jay, brilliant service and very much appreciated!!

Cheers
Mark