Copper washer XTR BR-M900: Function ? (with pictures)

Hi,

I have a new set (2 pairs) of the Cantilever brake BR-M900. The brake are in the original condition.

As you can see on the pictures there is a copper washer between the brake body and the bushing (I don't know the right term). Each of my brakes have this copper washer.







My question:

I stood out that both the Cantilever sockets and the bushings often have different length; the tolerances are up to 0,4 mm.
e.g. my front brake:
the left brake body works smoothy because there is a little space between the body and the bolt.
But the right brake body has no space, because of that the body is sanding at the bolt.

Is it possible that the copper washer was made to clear the tolerances and you can remove it if it's neccessary ?

Best regards
Christian

good question becaue I also have one m900 brake like that, if I tighten the stud bolt up properly the brake binds so I leave it slightly loose and worry about it undoing.

I'm no expert so can only surmise. :roll: The brake arms (and therefore the bushes) are bolted to the brake mounts, the arms rotate around the bushes, copper being a soft metal is ideal to use as a washer to take any wear rather than that part of the arm. How's that sound?

Mind you, it would probably take years to wear out !

On a couple of occasions where the boss has seemed a little short and the brake has bound when the bolt was tightened down, I've backed the bolt off and used some threadlock to stop everything falling off at an inappropriate moment. Worked for me.

cherrybomb":1gwbgogn said:

On a couple of occasions where the boss has seemed a little short and the brake has bound when the bolt was tightened down, I've backed the bolt off and used some threadlock to stop everything falling off at an inappropriate moment. Worked for me.

Click to expand...

That's what I'd do too.

You are right, it is possible that the movement of the brake can loosen the bolt if it fits to strong. To use a theatlock is ok.

But I don't want to damage the facing of the brake. For me it's more important.

Where these part a full set (front and rear) as the 'rear' are different to the 'front'.
That's a front one in the picture, try swapping that middle part around until they, hopefully, work well.
(they stopped the front/rear difference in '95 with the FD-900C, but you would also have cartridge type pads.)

It seems that the adjustable brake bodies (with the adjusterbolt) works fine.

But on the other side the bolt fits too strong - front and rear !