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Old 04-03-15, 10:48 PM   #1
Bibio
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Default 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.
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Old 04-03-15, 11:51 PM   #2
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Default Re: brake pistons

Weight I guess!.


A nut welded in the bottom could work.
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Old 05-03-15, 07:26 AM   #3
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Default Re: brake pistons

I would say weight. Daft as it sounds that's a good idea
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Old 05-03-15, 08:34 AM   #4
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Default 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.
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Old 05-03-15, 11:47 AM   #5
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Default 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.

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Old 05-03-15, 11:59 AM   #6
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Default 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.
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Old 05-03-15, 12:20 PM   #7
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Default Re: brake pistons

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Originally Posted by shiftin_gear98 View Post
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.
Aren't they cast? Therefore huge material savings.
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Old 05-03-15, 12:26 PM   #8
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Default Re: brake pistons

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Originally Posted by ophic View Post
Aren't they cast? Therefore huge material savings.
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
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Old 05-03-15, 01:46 PM   #9
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Default 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?
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Old 05-03-15, 02:41 PM   #10
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Default Re: brake pistons

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Originally Posted by _Stretchie_ View Post
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?
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


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