E30 325i Brake Master Cylinder upgrade

[colenot]

Does anybody have a suggestion for upgrading a brake master cylinder for an E30 325i? The seals on mine have gone following an over enthusiastic run at donnington! The car is a fully stripped out 89' 325i, used pretty much for trackdays only.

I have heard that the E30 M3 master cylinder has a larger bore, hence better braking... does anybody know if it is the same fitment as the standard master cylinder? or will it be a difficult fit?

Or does anybody know of a better alternative?

Any help or advice greatly appreicated!

[ian332isport]

An upgraded (larger bore) master cylinder will not give better braking as such. It will reduce pedal travel, but will also increase pedal effort.

Most professional drivers tend to prefer a hard pedal, as it's supposed to be easier to modulate, but I guess it's down to personal preference. As for what cylinder to use, you have a choice of two really.

1 - The 23mm E30 M3 cylinder will bolt onto the servo the same as the standard one, but you need to change one of the hard brake lines to connect it up. For some reason, the M3 cylinder has two different sized fittings (10mm & 12mm), where as the regular E30 has a pair of 10mm fittings.

2 - The 25mm cylinder from an E32 750i. This is a simple plug 'n' play swap for the standard E30 cylinder. It uses the same sized fittings for both pipes.

I think the 25mm cylinder may be a bit extreme if the rest of the system is standard. It's very useful if you have larger calipers though. The 23mm is probably the best compromise.

Cheers,

Ian.

[Karan]

ian do u think stock master cylinder would be poor with e30 m3 brake setup (calipers etc...)

is stock 22mm?

[Jhonno]

ian do u think stock master cylinder would be poor with e30 m3 brake setup (calipers etc...)

is stock 22mm?

no it isnt

[ian332isport]

ian do u think stock master cylinder would be poor with e30 m3 brake setup (calipers etc...)

is stock 22mm?

Karan,

It should be okay really. It's not like the M3 has huge calipers or anything. I guess if you tried an M3 pedal, and then an E30 with M3 brakes but standard E30 cylinder, you may notice a slight difference in pedal travel/effort. Nothing to be worried about though.

The E30 cylinder size is actually a bit more complex than just saying it's 22mm. On pre facelift cars, they had a 20.64mm bore for front and back brakes. After the facelift, they introduced a split bore cylinder that was 17.46mm for the rear brakes, and 22.20mm for the fronts. I don't know why they made this change, or what other changes they made to the rest of the system.

Both the M3 (23.81mm) and the 750i (25.4mm) are of a single bore design. Either of these cylinders if fitted to a post facelift car will change the brake bias sligtly, but I'm not sure if this makes a noticable difference on the road. My only experience with the 25.4mm cylinder is on my car, but the rest of the system is rather non standard, so does not really apply to most cases.

There's a really good write up here, but it does not cover the regular E30 split bore cylinder.

http://e30m3performance.com/installs/in ... c/25mc.htm

Cheers,

Ian.

[Karan]

cheers Ian i getit now!

[colenot]

Ian / Karan thanks for your responses. Now have the M3 cylinder and replacement piping ordered.... looking forward to feeling the difference!