brake pistons
 

why are brake pistons cupped?

why not have them solid with a thread tapped in the middle so you can pull them out with a bolt.

Re: brake pistons
 

Weight I guess!.


A nut welded in the bottom could work.

Re: brake pistons
 

I would say weight. Daft as it sounds that's a good idea

Re: brake pistons
 

I'd also have said weight,

why not machine a thread on the inside of the cup or a bit you could thread a bolt into like Bib say to make extraction easier.

Re: brake pistons
 

I'm going to go with weight and cost ;)

A lump of steel that size would weigh a fair bit, cost a lot more and store heat from the braking action more readily.

Jambo

Re: brake pistons
 

Definitely weight, and I go with the heat issue too. But not cost. I'd cost the same to but a thread in as it would to bore it all out in the first place.

Re: brake pistons
 

Aren't they cast? Therefore huge material savings.

Re: brake pistons
 

To answer my own question, apparently not, according to youtube.
However there's so much machining going on that I don't think boring them out would add much to the cost.

https://www.youtube.com/watch?v=jrazNLUIQIM

Re: brake pistons
 

The pistons on a Kwak we bought years ago were hollow, as normal, but there was also some sort of insert in there.

I never got around to working on that one so never got to investigate, any Kwak owners know what I mean?

Re: brake pistons
 

I seem to remember the rear caliper piston on the ZX6R 01 had a plastic insert which was the contact surface to the brake pad.

Looked a bit like this
http://www.partsnmore.com/images/parts/480/29-0519.jpg

Jambo