Topic: Oy Ring Mystery

[thelowmax]

So, I took apart my front brake to do some maintenance on it. When I went to put it all back together, I noticed that the rubber ring had somehow grown too big to be put back in. I used no solvents or cleaners on it. Anybody have an explanation?

[flybox1]

piston seal.  thats odd..
its a good idea to replace that $5 part when servicing your brakes. 
keeps all the good stuff in and your caliper retracting properly.

[thelowmax]

piston seal.  thats odd..
its a good idea to replace that $5 part when servicing your brakes. 
keeps all the good stuff in and your caliper retracting properly.

I usually do replace parts like this but it looked in good shape, other than the mysterious growth. Luckily I had already bought one for "just in case".

[lucky]

So, I took apart my front brake to do some maintenance on it. When I went to put it all back together, I noticed that the rubber ring had somehow grown too big to be put back in. I used no solvents or cleaners on it. Anybody have an explanation?

Brake cleaner (Trichlorethyelene) will cause rubber parts to swell up and be unuseable.
Carb cleaner which has the same ingredient will do the same thing.
Too much carb cleaner sprayed into the intake of a carb can the same problems too.

[kammery]

 It's possible the groove that the o-ring sits in in the caliper could have corrosion in it . The caliper on my 550  did that . Cleaned thr groove worked perfect .

[thelowmax]

It's possible the groove that the o-ring sits in in the caliper could have corrosion in it . The caliper on my 550  did that . Cleaned thr groove worked perfect .

 If you look closely at the picture, you will see that the seal, which should fit snugly around the piston, is a good 10+ centimeters larger. I'm betting on the brake cleaner theory.

[scottly]

I'm betting on the brake cleaner theory.

In your first post you stated you hadn't used solvents or cleaners??
What model 750? The K7/K8 have a larger piston than earlier models: 42.8mm vs 38mm.

[Black 750K8]

I'm betting on the brake cleaner theory.

In your first post you stated you hadn't used solvents or cleaners??
What model 750? The K7/K8 have a larger piston than earlier models: 42.8mm vs 38mm.

I'm with  scottly That is a big difference are you sure that is the same one you took out ? or did you maybe get it mixed up with a new one you bought?

[thelowmax]

I'm betting on the brake cleaner theory.

In your first post you stated you hadn't used solvents or cleaners??
What model 750? The K7/K8 have a larger piston than earlier models: 42.8mm vs 38mm.

I'm with  scottly That is a big difference are you sure that is the same one you took out ? or did you maybe get it mixed up with a new one you bought?

Sorry. I WAS doing two brake rebuilds at the same time but I took apart completely a k7 and just the brake caliper of a k8. I DID end up using the seal from one and the piston from the other but again, k7 and k8. I have, in the past, used brake cleaner on the calipers but when I took them apart, I just wiped the parts as I disassembled. Though, now I have to go to my shop to second guess myself. I'll be back.