Rear Caliper Puzzle: Pin & al.

[tmcafe]

After reading all the posts about the rear caliper troubles, I decided to give my caliper a good cleaning. Luigi's shop manual says drive out the pin with a punch and a hammer. Front calipers pins are visibly held in place by cotter pins, but I couldn't see such restraints in the rear. So in what's probably a Beavis-level decision, I took Luigi's word and hammered the pin out with a drift. I assumed it took forever because of the crud friction and perhaps some groove in the pin, activated by the spring. Turned out the pin did have some kind of clip. Here's what's on mine (kind of like a ring about 3/4 circumference of the groove it sits in):

 

 

Also cleaned both pin and spring as best I could but they're both stained (surface is smooth, they're more like discoloration patches):

 

 

Pads were fine; pistons didn't seem to have any crud, but gave them a good cleaning with brake fluid anyway (didn't want to use brake cleaner since smb said it may f up the seals)

 

So here's the puzzle (sorry if it's moronic ):

 

WTF is with that ring? Was it some "R" clip that got f'd up? Can it be replaced with a real or makeshift?

 

Is that blotchy look of the spring and pin okay?

 

Also (not directly connected), why does the rear pedal have a slight play downward (it doesn't fully return to the top position, but I can pull it up for a few mm of play). I've seen a solution with a spring on the M/C actuation rod (?)

 

Many thanks for suggestions.

[belfastguzzi]

From memory, it's just a round ring and yours probably has a section broken off: not an R clip or anything else. I could be wrong.

Also from memory, the pin can be tight and hard to get out.

 

Blotchiness looks ok. The ring may be a problem though.

 

On the pedal issue – some use a simple elastic band to pull the lever back up.

[tmcafe]

From memory, it's just a round ring and yours probably has a section broken off: not an R clip or anything else. I could be wrong.

Also from memory, the pin can be tight and hard to get out.

 

Blotchiness looks ok. The ring may be a problem though.

 

On the pedal issue – some use a simple elastic band to pull the lever back up.

Thanks BFG! If it's a ring, how's one supposed to deal with it, assuming it's there to keep the f'ing pin from sliding out? As it is, the 3/4 ring seems secure around the groove while it's loose enough to turn. But when I was trying to drive the pin out, there was no way I could wiggle it even a bit. Replacing the pin gives a little more control as the ring is on the outside. Still can't figure it out. If the caliper wasn't critical to safety, I wouldn't bother...

[Richard]

Thanks BFG! If it's a ring, how's one supposed to deal with it, assuming it's there to keep the f'ing pin from sliding out? As it is, the 3/4 ring seems secure around the groove while it's loose enough to turn. But when I was trying to drive the pin out, there was no way I could wiggle it even a bit. Replacing the pin gives a little more control as the ring is on the outside. Still can't figure it out. If the caliper wasn't critical to safety, I wouldn't bother...

There should be a hole in the other end of the pin so that you can wire-lock the pin in place. If you are worried about it, just wire-lock it once rebuilt.

[gavo]

After reading all the posts about the rear caliper troubles, I decided to give my caliper a good cleaning. Luigi's shop manual says drive out the pin with a punch and a hammer. Front calipers pins are visibly held in place by cotter pins, but I couldn't see such restraints in the rear. So in what's probably a Beavis-level decision, I took Luigi's word and hammered the pin out with a drift. I assumed it took forever because of the crud friction and perhaps some groove in the pin, activated by the spring. Turned out the pin did have some kind of clip. Here's what's on mine (kind of like a ring about 3/4 circumference of the groove it sits in):

 

 

Also cleaned both pin and spring as best I could but they're both stained (surface is smooth, they're more like discoloration patches):

 

 

Pads were fine; pistons didn't seem to have any crud, but gave them a good cleaning with brake fluid anyway (didn't want to use brake cleaner since smb said it may f up the seals)

 

So here's the puzzle (sorry if it's moronic ):

 

WTF is with that ring? Was it some "R" clip that got f'd up? Can it be replaced with a real or makeshift?

 

Is that blotchy look of the spring and pin okay?

 

Also (not directly connected), why does the rear pedal have a slight play downward (it doesn't fully return to the top position, but I can pull it up for a few mm of play). I've seen a solution with a spring on the M/C actuation rod (?)

 

Many thanks for suggestions.

 

Is the clip spring steel I've seen something similar on car calipers where the ring slots into a groove to stop the pin moving unless it is punched out

[tmcafe]

Thanks Richard and gavo. The ring looks like steel (closest resemblance would be something like regular paper clip profile). There's no hole anywhere on the pin. That would have been the place for a cotter pin. I could drill a hole with a very fine bit (dentist ?) and safety wire it. But I'd rather figure out what exactly is with the pin and ring.

 

The Brembo has some pdf instructions on how to change pads on the different types of bike calipers. On the type that is similar to ours, there's a clip, but it's shown as being extracted with needle-nose pliers from the outside of the pin.

[raz]

I may be wrong, but from memory my pin looks exactly like yours and it locks in a groove as gavo said. Maybe you've lost a mm of the ring but I'm not too sure about that. Did you try refitting it? When I tap it in I can feel the ring seating in the groove.

[dhansen]

I'd say gavo and raz are on the right track. The ring compresses slightly when reinstalling the pin then expands into a groove to lock the pin in place. Might even be able to see the groove in the caliper if you have a look..............

[mike wilson]

The ring slides right through the caliper section that the pin hole is in and then prevents the pin from sliding back out again. It compresses enough to go through the hole because a section of it is missing but it needs quite a good clout to do so - in both directions. If you look carefully at the pin hole in the caliper, you will see that it is slightly chamfered to give compressing the ring a start. The pin and ring condition are excellent - put them back in, with a smear of anti-sieze. You should see the ones I take out after a winter's use........

[tmcafe]

Thanks everybody. In the meantime I tapped the pin back in. Worked like a charm (had pin and spring smeared with a bit of brake grease beforehand). Guess it was just a lot of dried-up gunk. Little ring in groove worked as described. Glad to see that you guys confirm what I was hoping to be the case.