K75 caliper rebuild questions

[walendo]

Hi all, I'm replacing the front disks on my (non-abs) 1990 K75 and figured I'd rebuild the calipers while I had the bike on the stand as they looked like they could use the love.  I've never rebuilt a caliper before so it's a learning process for me. I've got the two calipers split, disassembled, reasonably clean and am now approaching the part where I have to put them all back together. I picked up the BMW rebuild kit that has the new dust rings, o-rings, cylinder rings (dunno what they're called) and bolts - and noticed it also comes with a packet of grease.

So... what do I do with the grease? The Haynes manual I have just says lube everything with break fluid. Is the grease meant to be between the piston and ring in the cylinder? Somewhere else?

Also, does anyone know if there's a torque spec for the bolts that hold the two halves of the caliper together? I don't see it my Haynes book.

Thanks in advance, -w

[Qdude]

I cannot imagine what that grease would be for... Why would you want to have grease in a spot where it could get to the disks anyhow?

I have always done what your manual recommended and lubed up the rubber with brake fluid. I have rebuilt many calipers before, but never one off of a BMW. I wonder if the packet contains some substance other than grease. Maybe it is specially formulated by BMW to be compatible with the brake fluid.

I would cautiously say that you would be safe to assemble the caliper without using the "grease".

Now I won't be able to sleep 'til someone more knowledgeable chimes in.

[pdg]

Brake assembly grease, used around seals, pistons etc. Compatible with brake fluid and the rubber used. Often red in colour...

Good stuff if used correctly, more slippery than brake fluid so makes it easier to assemble parts and get them to seat properly without catching and pulling out of position.

(This point is debatable) also helps to lube the pistons and makes them slide in/out easier.

HTH :2thumbup:

[walendo]

Awesome, thanks. So I can use it around the rings as needed, and not worry about it mixing with the DOT-4 brake fluid. Sounds like getting a film on the piston wouldn't hurt, either.

Here's a pic of the packet:


 

Thanks again!

[pdg]

No probs - don't go mad with it though, it's only a smear of it you need/want.