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Brake Job

Bwana

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In the midst of re-doing the brakes on my '72 CSi. Going well so far but I have a question on the piston orientation. The pad side of the pistons have a cut out. What is the orientation supposed to be or does it matter?

Here is a shot of the piston, you can just see the cutout



Here is the rust pattern on the back of the pads. They seem to have a specific orientation.


 

MMercury

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In the midst of re-doing the brakes on my '72 CSi. Going well so far but I have a question on the piston orientation. The pad side of the pistons have a cut out. What is the orientation supposed to be or does it matter?

This topic is covered in the shop manual.

There is a 20 degree orientation. You should be able to use the brake pad shims you pictured to correctly reorient the pistons.

The significance of the cut out is discussed here:
http://www.e9coupe.com/forum/showthread.php?t=3471 :wink:

FWIW, this picture (for a 911) should give you an idea of how you might check the piston orientation. If you were to flip the picture upside down, it would more accurately depict checking the E9 rear calipers.
 

Bwana

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Master Cylinder

OK, another couple of questions (it's been a while since I've done a major brake job). I'm rebuilding the master cylinder. Probably a good thing as when I pulled out the old assembly, a LOT of gunk came out too. So I'm installing the new assembly after soaking it in new, clean brake fluid.

Two questions
1) Where does the external pin hit along the assembly? When lined up externally, it appears it should retain the lower assembly in the bottom of the casting. Yes? The "land" in the picture is where it appears it should make contact.

2) I pushed both sections in at once. It appears that the lower section got "stuck" in the bottom as I can remove the upper section without the lower section coming out too. When I disassembled it the first time I remember having trouble getting the bottom section out, think I had to use air to push it out at first. I installed the upper section and screwed in the pin. The action now feels right and the length appears to be OK too. Should I worry about the lower section appearing to "stick" in place without the pin being screwed in or is there some sort of mechinism that sets it in place?



 

Bwana

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OK guys and gals, 188 views and no comments? I'm right on the verge of deciding to take it back apart or just install it. A suggestion from a BTDT person to tip to one side or the other?
 

Bertocchi

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The first segment of the plunger, which describe as the land, goes in and then the bolt, which you call pin, gets tightened down. This prevents the first segment from moving out of position during assembly of the second segment.
I am assuming that you are using a brake hone and brake fluid as your honing oil? It is also very important to look for pitting or rust rings in the inside bore. I use my fingernail to feel for them. Any such imperfections in the bore finish will cause the rubber seals to wear prematurely by acting as an abrasive.
The hone should clean up many of those flaws but if the bore is badly pitted the cylinder should be sleeved or replaced. Not much else to it. Put it back just as it was removed.
 

Bertocchi

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After waiting for three weeks I finally got my master cylinder rebuild kit and it is wrong. 22.2 MM instead of 23.8 MM. Yours looks like the 23.8? Where did you get it?
 

Bwana

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After waiting for three weeks I finally got my master cylinder rebuild kit and it is wrong. 22.2 MM instead of 23.8 MM. Yours looks like the 23.8? Where did you get it?
I think it is, I too got it on the second try. I actually got it from my local BMW dealer parts guy. He's "young like me" too and is a wizz at finding e9 parts. He worker for BMW when these cars were new! Can't remember how much it was, didn't seem too bad at the time. Nice thing about the dealer, he's down the street and if there's a screw up, he just restocks it. Just have to watch out for some of the real spendy stuff.

Do you know what dimension the 23.8 refers to?

But DON'T buy axle boots from BMW! $60 each w/o grease. I think $19 or so from Mesa.
 

Bertocchi

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I ended up finding a brand new item with Mesa Performance. They were very helpful and had everything in stock.
Being a Neophyte of sorts I thought Maximillian was the way to go. Factory authorized and all but everything seems expensive and in Germany?:confused:
 

HB Chris

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Mesa is a great resource and the type of small business that we need to keep around. I am fortunate in that they are only 10 minutes away. Don't expect instant gratification on the phone, they take their time but they do it right.
 

CookeD

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Hey All,

Have a '72 Bavaria project going, and a this is a timely thread, as I'd like to rebuild the brake master.

A couple of questions between the different master cylinders... Is the 23.8 diameter for rear disc vs. the smaller diameter for drum application? Or, was there a running change that didn't correspond to the rear disc brake upgrade, and one must remove the master and measure the diameter of the bore to get the correct kit?

Also, is the brake master the same for CS and Bavaria applications, if rear disc?

Thanks in advance!
 

Bertocchi

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Does anyone have a source for OEM style brake hoses? I have looked through most of the links and have found only Stainless hoses?
 
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