Everything you wanted to know about brake boosters and master cylinders

[325Projectz]

Are you thinking of the 750 mc?

[cheades]

Mine with the 320i booster will lock the brakes, but I am thinking about doing the 735i MC to stiffen up the brake pedal. Are the 735i and e34 M5 MC the same size?

[ptownTSI]

what is the part number on the 325ix booster? i put the part # Item Number 34331156978 in and got this (from bmaparts):
BMW018673
Main Category: BMW
Sub Category: BRAKE COMPONENTS / WHEELS
Qualifier: 325IX (E30) 1987 - 1991
Description: MASTER CYLINDER

Manufacturer: ATE
List Price: $323.00
Your Price: $ 139.52
Core Price:
Weight: 1.650

but when i searched on pelican, it came up as this:

Master Cylinder, Girling, 525i (With M20 Engine)(1989-90), 525i/Touring (With M50 Engine) (to 09/91), 535i (1989-92), M5 (1991-93)
Brand: Ate [Photo]

34-33-1-156-978-M4 $135.25

[Ryan Stewart]

I am also runnin the E34 M5/IX setup but I used soft hoses and its mounted to the blower cover above the booster.

I didnt measure the bore of the E34 MC but it feels like the 735i MC mod on the regular E30 booster. Its very quick and firm, dunno if that is a good or bad thing. I guess, since I can still threshold brake it, its not wholly bad.

[equate975]

Yeah,

Stock e30 m3 is 23
Stock e34 m5 is 25

[Rev Engineer]

Huh....

When I was talking about this a month or so ago I heard a ton of people say the 320i booster would not lock the brakes.

Guess I r3ved myself.

Being able to lock the brakes depends on a few factors - one of which being tires. It can be easy to lock up street tires, but hot and sticky tires can be a different story. At times I've had difficulty locking up A032's with the stock brakes on my e30 m3. Having experienced that, I'm going to shy away from the 320i booster with my s50 -> e30 m3 conversion. I'm also concerned about the 325ix booster with the ix master cylinder. I didn't know the e34 m5 master cylinder was an option. Does anyone know what the diameter of the bore is compared to the e30 m3?

[equate975]

I would disagree.

Huh....

When I was talking about this a month or so ago I heard a ton of people say the 320i booster would not lock the brakes.

Guess I r3ved myself.

[KangamangusDriver]

Any pics of how the lines attach to the resevoir?

Thanks for the write up! This will clarify the brake setup for the M/S swaps.

This is awesome!

[1990m3]

I'm with Jason on this one as I've driven his car with the 320i booster and that's what I chose for my project. I hit the brakes hard, it stopped fine, no problems at all. Matter of fact, it brakes just as well as my M3, which has extremely good brakes on it.

If you've been in a car that doesn't lock brakes maybe the owner should try bleeding the system again. Check s14.net for an excellent writeup on how to adjust play in the brake pedal, maybe it's needs adjustment

[Jason89i]

Cons: .......... Supposedly, will not give full lock to the brakes

Im not going to say much about this, because its a stupid way to do it.

Thanks for the ix booster write up. Good work.

However, I would recommend only giving advice on things you have "hands on" experience. spreading rumors (on a tech forum) because you heard somebody else didnt like it.....doesnt help.

ditch the metal masters and get some decent pads. on the street, running in the advanced group, abs, no abs, 4lug or 5lug......no problems with the e21 booster. (3 different conversions).

cheers, jason

EDIT: i just re-read what i wrote. sounded a little harsh. sorry, that wasnt my intention.......nice write up. thanks.

[puusitalo]

I would disagree.

Me too, at least until better explanation is given !

Petteri

[325Projectz]

Im not going to say much about this, because its a stupid way to do it.

I would disagree.

[Garageaholic]

Great writeup ,thanx

[xLibelle]

a friend of mine suggested that DSM (eclipse/talon/etc) plugs might be the same fitting. they are easy to come by in the yards. but new is always nice

[equate975]

Ok once and for all, here it is!

Option 1:

Use the e21 booster

Pros: Reuse old Master Cylinder, No remote reservoir

Cons: You will have to cut the shaft down to match that of the stock booster. Supposedly, will not give full lock to the brakes

Im not going to say much about this, because its a stupid way to do it.


Option 2:

Use the e30 325IX booster.

Pros: Its better than the e21, double drum design

Cons: Remote reservoir


How To:

Get yourself an e30 325IX brake booster, I used an e34 m5 master cylinder part number 34331156978.

For the remote res.

http://www.realoem.com/bmw/showparts...34&fg=25&hl=15

GET THESE:
05 EXPANSION TANK GIRLING 1 34321160576
02 PLUG 2 34311163464 WILL NEED TWO OF THESE


Here is the parts




Put your booster and new master cylinder together, then it all just pushes together





I found that where I have my reservoir now, the lines can get caught in the throttle body linkage, also they get in the way of the intake boot

The best place I can find to mount it would be on the plate where the old airbox attached next to the ABS unit