new brake pistons

[GZXR400]

So today i stripped my brakes as when i tried to clean my pistons the tops started to peel apart, removed the calipers and got the pistons out but a few were so stuck they had to be removed with molegrips.

This has put a few scratches in the pistons on the side nearest to where the pads would be, i have cleaned them up and got the rust of the tops but there are small holes there still

I will put some pictures up tomorow but i want to know if there going to be any good, i will defiantly get new seals but pistons are expensive, having said that brakes are important and cant have them fail, once again sorry for no pics thanks

[unitynotsocri...]

if you've scratched the pistons you can fine sand the scratches back down if they re not too deep.scratches on the top of the piston are far less critical as this bit is usually exposed to air and not hydraulic fluid.
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[GZXR400]

Hi iv been told the pistons are fine so i will be reusing them

i have removed the seals and spent a good few hours trying to remove all the dirt from the calipers, absolute nightmare iv been using brake cleaner with a toothbrush and also tried soapy water and still cant get it off

https://img341.imageshack.us/img341/9364/20120911165351.jpg

[_Iain_]

long as its clean inside where the fluid goes, i'd not be bothered tbh
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Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[GZXR400]

yeah theres a few brisles from the toothbrush i found just hope theres no inside where the fluid does

[Raffles]

[GZXR400]

ahh right awesome il get a seal kit ordered then

these are the pistons iv been told these are ok though

this is the worst piston

https://img402.imageshack.us/img402/2640/dsc0038edit.jpg

[Frost]

That's a nasty mark, but i don't think it's far enough down the piston to matter. When fully pushed in the seals only come up so far on the piston and i think the mark isn't on that surface. Once some pads are in there and the pistons pumped out a bit it'll be clear for sure.

Remember to coat the seal in brake fluid during reassembly as that's what they use for lube.

[GZXR400]

I know its concerning me a bit, there was no way i could get the pistons out tried compressed air and in the end they had to be pulled out with molegrips.

and ok will coat them in brake fluid do i need to use any sort of grease when fitting the new seals ?

Thanks

[Frost]

For future reference the best way to push pistons out is to use the system purpose built for it, the braking system!
Stick a screw driver where the disc would go on the calliper and pump the pistons out onto it. If you're careful you can get all the pistons 99% out and they will literally fallout when you remove the screw driver.

[GZXR400]

yes i tried this but couldnt get them to come out evenly im rather annoyed with myself iv took chunks out of my pistons. is a brake master cylinder seal kit needed aswell ? thanks

[stonesie]

[Fizzer Thou]

https://www.mandp.co.uk/products/list/Spares/Brake-Piston-with-Seals
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Just talk bikes.What else is there?

Always have a 'Plan B'

[GZXR400]

iv been told to use only geniune pistons these are 37 quid each

[Budgetboy]

Pistons are pitons mate,, its the seals you dont want to skimp on.Cheap seals will leak so get good ones.

Dont forget to clean the grooves out on the piston seal area.Red rubber grease when fitting new pistons as well.

If it were me i would add in the split caliper seals (half seals). like a small o ring.
And if you wanted to clean the years of brake dust from the caliper you will need to bead blast it IMO.
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[stinkwheel]

[GZXR400]

[GZXR400]

[stonesie]

Try some Mr Muscle oven cleaner

If you haven't got any in the house then add a pair of marigolds to the shopping list and some really cheap stiff brushes (not metal bristles).

[Vincent]

[GZXR400]

Are there any real differences in brake fluid brands for example castrol dot 4 fluid at £10 or £5-£6 universal fluid ?

[Frost]

Provided they're both DOT4 there won't be much difference at all. Maybe a slight change in the boiling point, but unless you're doing track days there's no point at all. Use generic stuff and you won't be afraid of wasting some as you properly bleed the brakes.

[GZXR400]

bit of a problem, rebuilt calipers with new seals and pistons, new pads and pins, took about 2hrs to bleed but brake lever still spongy.

Noticed brake fluid leaking from one of the calipers so looks like a piston is leaking

what now ?

[herulach]

[GZXR400]

all seals are defiantly in there as i have none left and i remember putting 2 seals in each piston hole and the caliper half seals.

Is is possible that my half seal has moved when tightening up the assemble bolts ?