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

Re: brake pistons
 

As a hollow unit, is the expansion due to heat more linear? I can imagine that this is also because there is less material to absorb heat from the pad making it less of a heat sink. This is only a thought though.

Re: brake pistons
 

Yeah that's it, I was dying to know, it was a track bike we (Me, Grunty and Squirrel) bought but life went wrong and everything had to be sold :( so I never got a chance to work on it

Re: brake pistons
 

i dont think brake pistons are cast i think they are drop forged then machined.

seems that everyone thinks it for weight and heat so far.

Re: brake pistons
 

Any motorcycles use ceramic Pistons? The brakes on my mountain bike use ceramic Pistons which stops any corrosion issues.

Re: brake pistons
 

the radial GSXR ones have a teflon coating

Re: brake pistons
 

Ceramic would be too brittle for motorcycles

Re: brake pistons
 

I was under the impression some Honda bikes had ceramic pistons. Could be wrong.

Jambo

Sent without a real keyboard

Re: brake pistons
 

Maybe ceramic coated?

Re: brake pistons
 

ceramics have come a long long way in recent years and they now make high speed bearings with it. the new bread of ceramics are tough as fek.

Re: brake pistons
 

That is true.
I think it's years away before being viable for vehicles. Saying that if they start using them in WSB or BSB, it'll be 5 years from then before brembo produce a road suitable version

Re: brake pistons
 

One of the benefits of ceramic bearings (besides lower rolling friction) is cool running. Maybe running cool helps keep friction down?

Ceramic brake pistons probably don't transfer much heat to the brake fluid, which is a good thing.

Re: brake pistons
 

Good suitable road going brakes are here now. If you need racing brakes on your street bike, you should take it to the track. Actually modern sport bikes have racing brakes from the factory.
If ceramic pistons were cheaper, we'd likely have them now on everything. If they work better, then WSB and GP bikes already have them.

Hard braking at every corner, especially from high speeds, will sometimes overheat common brake fluids, but you can use uncommon fluids if you're racing, and if your street riding includes hard braking from high speeds at every corner... wouldn't you be racing on street circuits?

Re: brake pistons
 

And maybe dissipate heat quicker than metal pistons?

Probably lighter too?

Re: brake pistons
 

I think they might use impact extrusion to make the rough shape and then turn them on a lathe to get the dimensions more accurate. It'd save tooling costs over turning them from a solid piece.

They're probably hollow to save money on material as well as reduce expansion effects

Bikerstoolbox.co.uk sell different tools to suit your budget, I just got the mole grip type tool since the cheaper ones were rubbish.