Refinishing/machining brake pistons

[D O G]

Right, getting stuck into the SRAD's brakes as I may just be able to spend the cash on it before the end of summer. I have 4 pistons which are too damaged to reuse (pits/damage from removal). Annoyingly they are 20 squid each.

Just wondering if anyone knows whether pistons can be lightly machined then plated back to original spec? Kinda hoping it may be cheaper, and would save chucking the existing ones in the bin.

Ta.

[sickpup]

There isn't normally a coating except on the early Honda Bakelite pistons. If they need machining they are dead but they rarely need machining just refinishing with a wire brush fitting on a bench grinder.

[bacon]

Are they 6 pot calipers?

If so dont bother spending any money on them.

Find some 4 pot nissin calipers from a bandit 1200/gsxr slingshot etc and fit those. they are fantastic brakes. I managed to find a pair for my zx7r last year for £42 delivered on ebay with a brand new set of ferodo pads.

6 Pots are great when they work, but the weather destroys them pretty quickly

[Teflon-Mike]

Yes, is the simple answer, same process are rechroming fork stansions. as to expense.... probably like fork stansions, if you can get new ones, usually cheaper!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[prawny1]

If they are just a bit damaged on the lip you may well get away with reusing the because the piston are only ever fully home when being serviced under normal use the pistons will sit out a few mm even on brand new pads.

Also the main fliud seal sits a good few mm in from the edge of the caliper face anyway so unless they are very bad you are only likely touching the dust seal anyway, if they don't leak or bind after being refitted they will be fine.

If you want you can take some measurement to make sure the damage clears the seals, just measure the disc and pad thickness and take that away from the width of the caliper mouth, the answer will tell you how far the piston protrude on new pads.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[D O G]

[MaybeGuy]

if you can ''lightly machine'' your old ones, why can't you just make new ones? TBH there's not many things simpler than a brake piston.
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[D O G]

I can't do it - but a specialist probably would. I was trying to find out if this had been done before by anyone on here.

Don't suppose you fancy making a set of pistons up from stainless, on the cheap?

[Serendipity]

I’m just going through the same dilemma with my old CBR6. I’m going to replace the original rubber hoses with new lines from HEL and I’ve been cleaning up the callipers. I popped out my seals and they’re in excellent condition and reusable once I’ve cleaned the corrosion out of the seats, but my pistons are rather pitted around the top few mm.

However as mentioned above, the pitting on my pistons is only on the bits constantly exposed to the elements so I’ve just cleaned them up as best I can and I plan to give them a go.

How much of the damage to yours is pitting and how much from removal?
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Teflon-Mike]

[Pete.]

There's not a plastics cat in hell's chance of a brake caliper seal ever popping out no matter how old it is. They have an oversize section compared to normal seals and there's almost no clearance between the piston and bore.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Serendipity]

Well while I can't see one of the fat fluid seals popping out I have experience of dust seals being pulled out after sticking to the piston.

To be fair Teflon has a point. It's not worth fecking about with brake systems for the sake of a few quid. However I know what I'm like with buying parts online. I'll start with seals, move on to new pistons and end up buying new bleed nipples and all new rubbers, pins and springs. Yeah, brakes as good as new, but my pocket lighter by the best part of £150.

The only reason I was considering reusing these seals was that I only fitted them about 1,000 miles ago and they were still well lubed with red rubber grease. However the bike has been stood for nearly five years so I ought to do the right thing and replace them. Last thing I want is to put it all together just to have the brakes start to bind straight away.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Pete.]

Dust seals are a different beast altogether, they are narrow, made from a harder rubber and usually have a relief outboard of the seal groove to prevent the crap they (are supposed to) scrape off the pistons from packing into a tight gap. The reason these come out is because they get stuck to the piston by road dirt when people especially when people fit new pads without cleaning the crap off the pistons and dragged out of their grooves with the piston as the pads wear.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[prawny1]

dust seals usualy only pop out if the caliper is corroded forcing them out of the groove, this corrosion behind the seals is most of the time why brakes sieze on in the first place,

clearing the crap out of the grooves with some brake cleaner and if it's stubborn or corrroded sand paper is enough to free brakes off and using rubber grease under the seals keeps things free whilst helping to stave off further corrosion better than just using brake fluid.

I hardly ever replace seals in a caliper unless they had been split or obviosly damaged from debris most of the time so long as the caliper body is in good nick they don't leak and are perfectly servicable.

My little 400 had a leaky front caliper seal about two years ago so i stripped it gave it a good clean refitted the origional seals i've never had a problem since.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[D O G]

Thanks for thr general advice people, I'll try and clean up these mofos before buying new ones.

[0ddball]