82 R65 seized piston

[johnw12]

Hello everyone,

A quick brake pad change on my R65’s brembo became a lot more work than I bargained for when one of the pistons seized. Looking at the prices for new seals and pistons I realized that it wouldn’t be much more expensive to buy a new F08 caliper, which I’ve heard some people have swapped in. Does that make sense or should I just rebuild the existing caliper?

[Bob_Roller]

I had a piston seized in a Brembo caliper .
I separated the caliper and used compressed air it worked, be be ready for it .
Came out with more force than I expected .
I had the foresight to use a bunch of shop rags and towels it will create a mess .

[tunnelrider]

I've done Bob Roller's method using compressed air to blow out a piston also, sure does work.  I was also surprised about the force it came out with!

IMHO buying a caliper rebuild kit would be the way to go, the caliper's pretty easy to give a quick repaint.  But if as you say you can buy a new one for not much more, you'd save yourself a few hours work.

[Barry]

Welcome.

The benefit of a new F08 caliper is the larger piston size will improve the hydraulic ratio resulting in better brakes.  Spares availability going to be better too.

If you think the Brembo caliper parts are expensive then look at the Ate caliper prices that R65's used from model years 78 - 80. They make an even stronger case for an F08.

[georgesgiralt]

Hello,
The Brembo caliper BMW use on the R65 are different on the fixation holes between the right and left one.
One of them has the fixing holes of greater diameter to accommodate the special spacing washers to center the caliper on the braking disk. The famous "hat" washers which come in different thicknesses.
I wonder if the P08 have such difference and can be used directly on our R65 ?
I would rebuild the existing calipers (provided they can ) and use them if serviceable.

[dogshome]

The calipers and pistons were in good shape both sides, depite being seized on and seemingly immobile. I also used air, from my little tyre pump. The seals were swollen and there was a lot of waxy residue and bits form the 40 year old rubber parts causing the trouble.

The only issue I had was that the bleed valve had been stripped one side and couldn't be repaired - the taper at the bottom of the hole was mangled. I seem to think that the F08 had differences in mounting - plus no availability in the UK. At least on my dual disc bike.

A second hand one in average condition (i.e. seen beter days) popped up at an almost reasonable price, so I got that. It was also good when rebuilt.

[Tony Smith]

A couple of comments.

The top hat spacer/shims are an example of BMW making a solution to a non problem. I have never seen one in the wild and am firmly of the opinion that they are not needed.

Using compressed air to remove caliper pistons gives me the willies after an accident I had. I prefer to use a 10*1 greàse nipple and pump them out. The hydraulic pressure is immense and I have never seen a car or motorcycle caliper piston resist.

If you buy a new one make sure it comes with a certificate of authenticity, there are Chinese copies out there and they are not good

Grem8ca make a licensed copy for not much more than the cost of Chinese imposters.

A genuine Brembo has an annod9sed piston and a polished bore. In 99 out of every 100 stuck pistons polishing the piston and the bore with metal polish will cure them.

Seals can be bought by size on eBay for a fraction of BMW's price.

[georgesgiralt]

A couple of comments.

The top hat spacer/shims are an example of BMW making a solution to a non problem. I have never seen one in the wild and am firmly of the opinion that they are not needed.

Tony, I've to disagree with that.
Without spacers, the right caliper touches the rotor preventing not only wheel installation but braking altogether ;-)
On the left side I've to space (a bit) the rotor in order to clear the caliper (the shims are NLA from BMW).
And as I bought the bike new in 1984, it came out of Berlin like that.... (I've since replaced the front wheel because of an accident but the new one had same needs)
Of course as this is a tolerance stack problem, your motorcycle will be different.

[johnw12]

Thanks for the advice everyone. I used a compressor to get the pistons out and they looked okay other than a little grime. Gave them thorough clean and put new o-rings in, but unfortunately I can't get them to collapse completely, so I'll be taking them a part again... Maybe EME sent the wrong size? The bolts they included were too short, strangely.

[Bob_Roller]

Not to question your mechanical abilities, but did you use fresh brake fluid to lubricate the seals and piston ??

[dogshome]

I don't remember having any trouble getting the new seals in. Mine came with a little tube of special grease. Bolts too short suggests the wrong kit!

[Bob_Roller]

This is not the first time that I have heard of issues with EME piston seals .

[Kelvin]

With the bolts of different length: on my bikes the bolts that hold the callipers together are 60mm long, those that hold the callipers to the fork only 40mm. The ones in the kits that I've purchased are 60mm. Both are M10 allen key head. I'm hoping that you haven't assembled the callipers with the calliper mounting bolts.

My three LSs all have Brembo brakes. The 1983 bikes have 10mm mounting holes on the left calliper, but 12mm on the right. There is a top hat spacer/shim on the right to allow use of the same M10 bolts as are used on the left. The "brim" of the top hat is installed between the calliper and the fork boss so it moves the calliper out a bit.

The 1984 bike has 12mm holes on both callipers and top hat spacers fitted both sides.

I strongly suspect that BMW assembled these bikes from the spare parts bin, ATE callipers one day, Brembo 10mm the next, Brembo 12mm the day after that.

[georgesgiralt]

With the bolts of different length: on my bikes the bolts that hold the callipers together are 60mm long, those that hold the callipers to the fork only 40mm. The ones in the kits that I've purchased are 60mm. Both are M10 allen key head. I'm hoping that you haven't assembled the callipers with the calliper mounting bolts.

My three LSs all have Brembo brakes. The 1983 bikes have 10mm mounting holes on the left calliper, but 12mm on the right. There is a top hat spacer/shim on the right to allow use of the same M10 bolts as are used on the left. The "brim" of the top hat is installed between the calliper and the fork boss so it moves the calliper out a bit.

The 1984 bike has 12mm holes on both callipers and top hat spacers fitted both sides.

I strongly suspect that BMW assembled these bikes from the spare parts bin, ATE callipers one day, Brembo 10mm the next, Brembo 12mm the day after that.

Hello,
The top hat spacer comes in different thickness in order to place the center of the caliper "perfectly" in the middle of the disc. On some bikes (I've seen one) the thickness is very very thin, and other quite thick.
On my bike, with the thinnest, the caliper is in contact with the disc and I have to use a middle sized one in order to put the caliper where it belongs.
Have a nice and brigh riding day !