ATE caliper opened...

[disco51]

Since my pistons weren't retracting well, I decided to go ahead and take the caliper apart last night.  Pretty nasty inside as you can see from the picture.  The top part of the piston is rusting in one area.  I'm wondering if this piston is salvageable?  This is the side that was actually moving.  I need to go find some compressed air to get the other one out.  Any tips for cleaning it up?  Also, is it necessary to replace the rubber o-ring that doesn't come in the rebuild kit?  I found the old post with the aftermarket part number, but wasn't sure I wanted to order 100 of them especially if the piston isn't salvageable.
As always, thanks for the help.  I'm sure there will be more to come...

[Barry]

I salvaged mine by polishing out a small area of corrosion but it was nothing like as bad as yours.  In principle if the corroded area doesn't contact the caliper seal then it's OK to polish it out. I'd pop the piston back in and see how far up the seal comes  or you might just be able to measure it.

[montmil]

That O-ring in the caliper body, if it's like the different design ATE's on my R100S, is probably a square-section ring, rather than round.

Try some WD40 wet 400 on the rusty area of the piston. Since the corroded area sits above the seal, you may be able to save it. Avoid sanding on the "pristine" portions.

Worth a try to salvage it as new pistons are...[smiley=furious3.gif]pricey.

[Bob_Roller]

New pistons are no longer available for the ATE calipers, unless you happen to find some new old stock source .

I'll check with the local BMW dealer on Tuesday, just to confirm they are no longer available from BMW .

The only other source I found, was Motobins in the UK and they stopped selling them a few years ago, due to not enough demand for them .

If someone knows of a source, please post it !!!!!!!!!!

If you have a micrometer, measure the ATE piston diameter you have, there are some aftermarket sources for pistons, but no one has ever measured them to see if it is available without having to special order them .

A couple of members here purchased the o-rings in bulk, they seemed willing to sell off the excess they have, make a posting for them .

I've been holding off rebuilding my ATE calipers as long as I can, I'm sure I'll find the same corrosion on mine as well .

If you can find Brembo calipers for an R65, they will fit with no problems, rebuild kits and pistons are readily available for these calipers .

[Ed Miller]

If you have a micrometer, measure the ATE piston diameter you have, there are some aftermarket sources for pistons, but no one has ever measured them to see if it is available without having to special order them .

Plus 1....  I recently ran across my paper I got from that guy here in the U.S. who makes them from stainless steel, but I never measured mine when I had them out and I don't want to buy any without some confirmation that they will fit.  

[disco51]

Unfortunately, I do not own a micrometer.  Any clues who might have one in town - I still have the pistons out so I could take them by a shop to have the measurements done.  Just don't know where to take them.  Be more than happy to give back to the forum for once...

[Barry]

A large micrometer might be expensive to justify for occasional use but a half decent digital vernier caliper can be bought for 10 - 12$.  You'll wonder how you managed without one.

[Ed Miller]

A large micrometer might be expensive to justify for occasional use but a half decent digital vernier caliper can be bought for 10 - 12$.  You'll wonder how you managed without one.

Digital vernier?  I thought it was one or the other.  I have a plain jane German made vernier caliper, but I need a magnifying glass to read it any more.  

[Barry]

They tend to go by the popular name of digital vernier caliper and that's how many of the retailers describe them but I take your point that they don't actually employ a vernier scale like the old days.  My eyes are well past using one of those and even though the Engineer in me is attracted to the quality of the real vernier calipers, the digital variety is so much easier and quicker to use. I find the depth gauge versatile. After all every Airhead needs a depth gauge just to change the oil filter !!!  

[NorR65]

Motorworks have caliper pistons for ATE R45/R65.

http://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=20&Ct=HA&SbCt=BA_15_20_HA_30

[Bob_Roller]

For North American members, I believe that Motorworks has starting selling parts to the North American market .

So it looks like there is at least one source for these pistons .

[tvrla]

The Harbor Freight digital calipers are actually pretty accurate and cost about ten bucks.

That's good news about Motorworks! Looks like their ATE pistons are about $45 each before shipping.

I had some made up eight or nine years ago. The machinist made up a batch and I bought a couple from him. I'll have to see if he's got any left. They were stainless, of course.

[Ed Miller]

Julio says both the ATE and Brembo pistons for the R65 are 36 mm diameter, in this technical post:

http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1311933847

[Barry]

That was an excellent post by Julio.  Shame the dust seals are a different diameter but it sounds like the piston seals are interchangeable and maybe the Brembo piston could be used in an ATE caliper with the ATE dust seal.

[Ed Miller]

http://www.etypeparts.com/search?q=r65

Here's the web site for the guy here in the US who makes them from stainless.

That diameter converts to 35.941 mm.  The price has gone up to 24.20 since I found it before.  I wish somebody would buy some and compare.  If they are the same I would buy 4 for the next time I rebuild my brakes.