Brake Booster Master Cylinder Question

[///Mariani]

This has probably come up a million times before so please bare with me. So I chose the E30 325ix booster in order to clear the intake. Now all the Master Cylinders im seeing that mate with this new booster have two ports for the hard brake lines. <Please correct me if I am wrong about that. This whole build is on an 84 chassis with drums on the back. <Dont know if that really matters, but my old Brake Booster MC has three ports on it. And sure enough, there are three lines sitting at the Brake Booster, waiting to be screwed into a Master Cyl. Am I missing something? Did I F#ck up?

Real OEM shows that my original Mast Cyl has a stopper bolt on the bottom port leaving only two lines to be connected, but my car definitely has three lines. Following the lines on the car, the back two(at the booster) seem to be left and right front. The line that connects to the most forward end of the master cyl seems to disappear to the rear, so my guess is rear brakes. I must have overlooked something. Any help is appreciated thanks.

[nrubenstein]

T the line.

[///Mariani]

Thats what I was thinking. Now that Ive heard someone else suggest it, I have just enough confidence to do it.

[Link]

I don't know how I feel about adding the power and weight of a 24v with drum rear brakes..

[justin_l_]

The T from the rear brake line works great.

[///Mariani]

I don't know how I feel about adding the power and weight of a 24v with drum rear brakes..

Well Its on my list of things to do. I'll see how it turns out for now. Ive never liked the look of drums.

[The Dark Side of Will]

What are the MC piston diameters for the disk vice drum brakes?

If you use a large diameter piston designed to move a lot of fluid for disk brakes, you'll be applying the rear drums before you apply the front disks.

The iX booster won't accept your original MC?

[///Mariani]

What are the MC piston diameters for the disk vice drum brakes?

If you use a large diameter piston designed to move a lot of fluid for disk brakes, you'll be applying the rear drums before you apply the front disks.

The iX booster won't accept your original MC?

No flipping clue. But I searched for 325ix booster and came across this PN: 34311161859. My original MC is too small for the new Booster, so the one I need is def larger in diameter. And damn, I never thought of the rear brakes gripping first. Its going to be an interesting first ride.

[nrubenstein]

No flipping clue. But I searched for 325ix booster and came across this PN: 34311161859. My original MC is too small for the new Booster, so the one I need is def larger in diameter. And damn, I never thought of the rear brakes gripping first. Its going to be an interesting first ride.

Iirc, the old master is 20mm/20mm, so that'd be fine. The problem is that you would shift the bias further front (but you could play with that with a bias valve, or just do the smart thing and upgrade to rear discs).

[nando]

why don't you just change the brakes to later E30 parts? the ix master is the same as a 325i except for the mounting to the booster.

[///Mariani]

why don't you just change the brakes to later E30 parts? the ix master is the same as a 325i except for the mounting to the booster.

Like I said before, it is on my to do list, but right now, I am nearing the end of parts needed to get my swap out of paperweight status. And you cant tell me that you wouldnt drive it as soon as everything is hooked up despite the crumby brakes. At least I cant lol. I just want to test this thing out as soon as I can. Im not going to be thrashing it about just yet, but its been over a year now since I stared this whole thing and now im anxious.