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Wich type of BMW Brake Master Cylinder fits as a bolt on unit to our GTV's ? Does anyone knows if a BMW e30 s series or an e23 7 series will fit ? what is ther diameter ?

Tomer

E32, its 25.4mm from memory you will need to use a T fitting as these ones only have 2 ports Front/Rear, you're stock ATE master has 2 ports for the front brakes, one for rear. Get the resoviour too as its a easy fit, see photo = low fliud level float and port for clutch MC (if your car set up this way). Don't do this if the rest of your brake set up is stock! This is a solution to reduce pedal travel and improve feel (firmness etc) AFTER changing front caliper piston S/A size etc when stock master cylinder 22mm doesnt cope ie too much travel and not very firm etc
The only other note would be to get/check the booster push rod to MC sleeve depth the same. ie the BMW(ATE) MC sleeve is a little deeper so you're booster push rod won't seat an the end of the MC sleeve so the result is pushing the brake pedal that first bit does nothing till it gets seated an starts "working". I ended up using shims to get this right, and went from one extreme to the other in terms of pedal travel only. No shims pressed brake pedal maybe 1/4 to 1/3 of total travel before it was firm, too many shims and as soon as i touched the pedal its braked! I think about 5mm was right, you'll just have to test yourself to get it right and make sure you brakes don't drag.
Good luck with it i'm very happy with the improved pedal feel + travel.

I finally did this conversion on my Dads car to match the 4 spotters and 295 rotors on the front. It works well !
The simple solution to taking out the pedal slack is to get a booster with adjustable rod length - I'd never seen one until this one !

I'm thinking of buying one, and I came across this one:


Am I assuming correctly that this is just the same master that you guys both have, and I just need to unbolt it from the rear end and "tada!"? Or this is a different unit?
Daniel the booster with adjustable rod you have comes from a BMW? If yes does the booster bolts straight on?

The master cylinder you have there looks correct, just remove the hydraulic booster. The cylinder size is marked under the reservoir. From what I could find, the 25mm cylinder was only fitted to the 750 series BMs, the 730/733/735 only had 23mm ones.

The booster on Dad's GTV is genuine original 1985 Alfa.

Thanks

Installed BMW MC on alfa. And I'm not impressed to say at least. The feel is marginally better, but still there is a huge pedal travel and braking not impressive. I have replaced seals on all calipers, MC, new pads, new flex hoses... This would leave the metal brake hoses. Please tell me that these corrode, and make braking crap, and replacing them will help. If it doesn't I roll her off the cliff

what size did you have previously and what size did you swap it with?...i had a HUGE improvement on my 83 gtv6

any chance your calipers need rebuilt?

Hey Poland Pete,

Everything you have done is good towards the fix. Should have no regrets.
Excessive pedal travel and feel can be due to residual air in the lines. I have to assume you have thoroughly bled the system AND correctly.
If that is so, then the travel problem is one related to your master cylinder being too small in the bore. Does it exactly match the original? IF it does, go one millimetre bigger or even two if you don't mind a hard pedal. You can have your original master cylinder resleeved to go bigger by whatever amount you want. That way you can be sure that all the connections and stroke are correct.

For pads I use Hawk Black. They make noise at low speed and put crap on your rims but they sure stop which is the principle goal for brakes.

good point with the air in the system.....vacume bleeding is a must...but for the vacume pump to work well you need to teflon tape ALL of the bleed screws

One thing that can be a wee bit sneaky is the adyustment of the rear brakes......too tight and the car stands on its nose if you breathe on the pedal, too loose and you get the pedal on the floor before the car starts to slow down.

hth,
scott

First off, thank you all. For a sec I thougth that maybe I'm paranoid about all "this" but i guess that this video shows it all (and that's after the bigger MC install)
http://www.youtube.com/watch?v=y-ltsrRXKsk
Just to give the idea about travel/softness.
Heres the MC I've put in the car:

for comparison the old rusty stock MC (22mm) that i found in garbage.
As you can see the Beemer MC is visually larger in diameter. In fact, its a 24mm MC (this one came off a E28 528i)
Here are the pics of the MC installed

Concerning the bleednig i dont realy think I messed this up, ive flushed 3 liters of brake fluid this past 6 months through the system, yet bleeding was done the old two man way. Maybe vacuum bleeding is better?
(Btw some of you might have read my thread on alfabb. about the left wheel, well my joy was premature, alligning the lines correctly to the MC didn't help)
With all things done so far on the brakes, it just doesn't make bloody sense to me why the things are still like this.

i had the same problem and went and got a vac bleeder..after figureing out that it was sucking air past the threads of the bleed screws i teflon taped the bleeders and re-bleed the whole system till i got ZERO air out of any screw...the brakes have felt great ever since..

if cost is an issue there are several bleeders for 20-30$

putting the rear end of the car high in the air helps bleeding the brakes. the higher the better... The adjustement of the rear calipers is also important as mentioned above.

Ok, remember that all of these MCs are actually imperial
A 22mm is actually 22.2, a 24mm is 23.8 & a 25mm is 25.4mm
So the change from "22mm" to "24mm" is only a 15% increase in xsection (and therefore 15% pedal stroke reduction and 15% rise in pedal force) where the "25mm" is a 30% increase.