Everything you wanted to know about brake boosters and master cylinders

[FredK]

I believe the E32 735i or 750iL master cylinders are the same.

I used the PN 34 31 1 156 643 master, and the ETK shows it is used in both the 735 and 750.

[Van Westervelt]

I believe the E32 735i or 750iL master cylinders are the same.

I used the PN 34 31 1 156 643 master, and the ETK shows it is used in both the 735 and 750.

I pulled one from each, and can promise, they are not the same. Anyone who knows or has dont the 750i mc with a 320i booster?

[Mike B.]

The 750i M/C is going to be too much for the 320i booster. People complain about the pedal feel with the stock M/C. If you decide to go this route, be sure to use some sort of vacuum reservoir to help pedal feel.

[FredK]

I have the 34 31 1 156 643 master and the pedal is a lot stiffer than stock, but still plenty powerful, at least for the street. I am running M3 brakes.

The 750i MC that I am using has a 25 mm cylinder. It is identical to the one pictured on Gustave's site:

http://www.e30m3performance.com/installs/installs-1/25mc/25mc.htm

I recall running into this issue--there were a few different parts that were sort of similar, but I just went a PN with what had already been used successfully with E30s. I got my MC from BMA Parts.

[e30polak]

So confusing after reading all this.

Looking to run a e21 320i booster. I have a 735i master cyl, although I dont know what size, and a 750i 25mm master cyl. I would like to use the 25mm one from the 750i with the e21 320i booster. Anyone have any experience or is anyone running this setup?

All my understanding says it will, but after reading, I am now confused

i'm running the 320 i booster with a vacuum reserve canister, and that helped pedal feel alot. i'm about to put the 25mm mc and use rx-7 calipers with corrado rotors. with this the brakes will kick ass on nice pads and rotors :woowoo:

[nefarious7907]

I have heard on either e30.de or e30zone.net that VW Mk I GTi booster is a direct swap.

[Bmjpv]

Think about keeping it simple. Keep your stock power booster and just modify the under side of the plastic intake manifold! It's very easy to work with ,I used fiberglass and uv resin .This takes only a small amount of chamber enfringement space and no spacer are needed for the motor mounts,no trans misalignment and works on keeping the c/g down ,every little bit helps! And the car still haulass! Think about it. This has been mentined before by other but not really talked about. thanks joe

[PiercedE30]

Bmjpv: care to elaborate/post pictures on what you did?

[Bmjpv]

Yes, I'll get pics up with manifold installed. Pryer to 24v swap I got my brakes just the way I wanted them, started with 5 lug swap added the 25mm master (off 750i) and finished with metal flex lines. What I really like about the 25mm master it's more about volumn push and less pedal travel, I like the pedal effort (booster sizing, e30,OE) which in the end gives me less travel for better head & toe interaction .The bmw (e30) is really a drivers car and that's why we like'm .Its hard to improve on these cars and I felt braking performance (effort & modulation) were premier with me. I've heard of e30 swappers complain about not enough booster assist. This to me is, and can be very dangers when you can't get your car hauled down from speed! That's my SCCA sedan racing coming out of me. just my opinion . thanks joe

[MIKe30]

Yes, I'll get pics up with manifold installed. Pryer to 24v swap I got my brakes just the way I wanted them, started with 5 lug swap added the 25mm master (off 750i) and finished with metal flex lines. What I really like about the 25mm master it's more about volumn push and less pedal travel, I like the pedal effort (booster sizing, e30,OE) which in the end give me less travel for better head & toe interaction .The bmw (e30) is really a drivers car and that's why we like'm .Its hard to improve on these cars and I felt braking performance (effort & modulation) were premier with me. I've heard of e30 swapper complain about not enough booster assist. This to me is, and can be very dangers when you can't get your car hauled down from speed! That's my SCCA sedan racing coming out of me. just my opinion . thanks joe

got those pics?

I have heard on either e30.de or e30zone.net that VW Mk I GTi booster is a direct swap.

and can anyone confirm this?

[nefarious7907]

http://www.e3024v.com/project6.htm

3/4 of the way down

[Bmjpv]

Here are the pictures of the intake modifications I made to keep the original brake booster. I cut a portion of the manifold out and used fiberglass mat/ uv resin to mould a space for the brake booster. If you might think reshaping the under side of the manifold is wrong, you have to remember that everthing is a trade off and that I would take good brakes anyday of the week!




thanks,
joe

[drifty340i]

Im using a mk11 vw golf booster, bolts right up!

[PiercedE30]

Bmjpv: do you have any pictures from when you were doing the modifications?

[Bmjpv]

No sorry ,I didn't do anything like that,but what I did was guesstamate what my problem area was,I cut out,glassed and resin. I put non sticking plastic over the booster and put the manifold in place without bolting it to head (layed down lower for more finished clearance) and this gave me the shape. In the end of the manifold I cut a access plug to give me room to glass the inside,layered outside with glass as needed and sanded as needed. I'm happy with the outcome and I still love my brakes! The plastic manifold is real easy to work with, try this mod! good luck joe