I am sorting the brakes on my project CBR 1000 F 1987.
When I stripped the calipers, removed the pistons,and found metal thin metal discs in between the piston and brake pad. Upon closer inspection, one was a £1 coin (old size) and the other three were what looked like Bakelite discs covered with metal. What are they, are they replacing missing standard discs ? They are about 2 mm thick maximum. Can the pistons operate without them, can they beer bought separately/, as new pistons are very expensive. I will attempt to upload photo of this amazing bodge up.

 

Have a look at this seller matey
https://www.ebay.co.uk/itm/Caliper-r...YAAOSw0d9bS6kL

 

many thanks

 

If the piston were in direct contact with the pad you could develop a squeal when braking. By adding something between the piston and pad, it would eliminate or reduce that squealing.