s caliper rebuild help needed

[steven c]

Bought some S calipers and took them a part for new seals. Really very clean and didn't need seals but put them in, lubed them and tried putting the pistons back in. No go. The pistons are getting stuck on the needle that inserts into the back of the piston. Was I suppose to take this off the back of the piston and clean it or something? The rubber inside this piece is broken on both pistons? Feels like an air lock as you push the piston in and it is spongy and will not go further. I took the piston seal out to confirm it is the needle causing the problem. Never had this happen before...any help appreciated.

Thanks
Steve

[djpateman]

The knock-back mechanism always seems sticky. Lots of posts on this subject if you search. Be sure the caliper is vented of course. A C-clamp properly used works well.

There should be no rubber in the knock-back mechanism.

[Flieger]

Contact Eric Shea at PMB Performance with any questions about brakes, especially Aluminum S caliper rebuilds.

Member "Eric_Shea" here on Pelican.

A sample of his work:

[steven c]

Thanks guys, the responses help. My pistons are too rusty to reuse so I will order some new ones. The knock back springs are really stiff going over the needle. I have taken them off the pistons and will clean them really well before putting them on the new pistons. I also plan on using the Porsche paste for reassembly which I hope will make the knock back springs slip on easier. Will see about that?

[RWebb]

yes the porsche paste is the best - Bill V. has posted on it if yo need a p/n

you know aobut the stainless steel pistons for the S calipers...?

[steven c]

Originally Posted by RWebb

you know aobut the stainless steel pistons for the S calipers...?

Yes, just ordered a set yesterday as 3 of the 4 of mine had too many pits to trust on a race track! Thanks