Rear caliper piston corrosion

[MoteroNC]

I was wondering if others have seen this galvanic corrosion on rear caliper pistons. This is on my rear caliper 09 R1200rt. Thank you

[dirtrider]

23 minutes ago, MoteroNC said:

I was wondering if others have seen this galvanic corrosion on rear caliper pistons. This is on my rear caliper 09 R1200rt. Thank you

 

 

Afternoon MoteroNC

 

Wow, that looks bad, no I haven't seen any that bad before on the 1200 bikes. 

 

What does the back of the piston side  brake pad look like?

 

Were you using BMW brake pads, or good major brand brake pads, or lower quality off-brand brake pads?

[MoteroNC]

The pads look fine. I was using pads I got from beemerboneyard. I think they are Lorraine or EBC.

[dirtrider]

27 minutes ago, MoteroNC said:

The pads look fine. I was using pads I got from beemerboneyard. I think they are Lorraine or EBC.

 

Evening MoteroNC 

 

If the pads still look good on the back side then it probably isn't galvanic corrosion. Might be heat related.

 

I haven't ever seen those piston closeout inserts available separately, not even sure that you even need them as a lot of disk brake systems don't even use piston close outs.   

[MoteroNC]

Yep. By looking at marks in the pads it looks like the contact occurs around the perimeter. Do you know what material it may be? I could as a friend to do a weld repair at least to seal the surface. Thoughts.

[dirtrider]

1 minute ago, MoteroNC said:

Yep. By looking at marks in the pads it looks like the contact occurs around the perimeter. Do you know what material it may be? I could as a friend to do a weld repair at least to seal the surface. Thoughts.

 

Evening MoteroNC 

 

Some of the piston filler close out's are plastic & some are like a pot metal or tin, usually plastic on the organic brake packages due to less generated heat. 

 

You are not going to weld on those so just pry those piston fillers out then clean up the pistons (they don't apply any pad force, they just keep the crap out of the inside of the pistons).   

 

You can buy a piston & seal kit for the rear (I think). 

[MoteroNC]

Ok thank you. It definitely felt metallic as far as the dust. If it is a low level metal I can see what you mean by heat.

[dirtrider]

3 minutes ago, MoteroNC said:

Ok thank you. It definitely felt metallic as far as the dust. If it is a low level metal I can see what you mean by heat.

 

Evening MoteroNC 

 

I will correct myself, I just pulled up a picture of the 1200RT rear caliper & it does look like the those piston fillers do stick out far enough to push on the brake pads so you probably should have them.

 

It will probably work OK without the fillers but they do seem to contact the pads first so probably do some to reduce brake pad heat transfer into the pistons.

 

 

[MoteroNC]

Thanks DR. I will see if I can find a rebuild kit or a way to make some fillers. They do look metallic in your photo. 

[dirtrider]

15 minutes ago, MoteroNC said:

Thanks DR. I will see if I can find a rebuild kit or a way to make some fillers. They do look metallic in your photo. 

 

Evening MoteroNC 

 

You might also buy a used rear caliper off of E-Bay.

 

If you shop right you might even find a good used caliper complete with nice looking brake pads. 

 

Here's one that popped up with a quick search (free shipping). You would need to verify that the caliper fits your motorcycle.

 

It shows a caliper but sort of says bracket so you would need to confirm that it ACTUALLY is the caliper & bracket.

 

 https://www.ebay.com/itm/2007-07-09-BMW-R1200RT-R1200-REAR-BRAKE-CALIPER-BACK-BRACKET-MOUNT/333070783751?fits=Make%3ABMW&hash=item4d8c90d507:g:K6UAAOSwbF1bwRnd

[MoteroNC]

Thank you DR

[14TLC]

I have seen many rear brake calipers in such state on both R1200 and K1200/1300.

 

All of them were in that state due to overheating. In some cases the overheating was due to brake pads with inadequate friction material wearing out completely in short mileage (in some cases in just 5.000Km) .

 

Some owners are not aware that these bikes have integral braking system and they are just puzzled by the fact that the rear brake pad has been completely worn in such short mileage even when they are using mostly front brake.

 

In other cases the overheating was due to stuck slide pins of the brake calipers causing limited or no floating of the caliper. From time to time you should check whether the brake caliper floats. It is very easy by pushing the caliper towards the brake disk. If they are stuck you should check the slide pins for corrosion, not enough lubrication, dirt and damaged protection rubbers.