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Brake caliper pistons

hampshirehog

hampshirehog

Forum Sage
Past Site Supporter
I've just bought a secondhand set of front calipers from a 1985 GSX750ES (reputedly) in good condition. They bolt straight on my GS1000 (with the GSX750 slotted discs fitted). The new calipers have got, however, completely rusted pistons which need replacing. In my pile of old and new bits I've found a new pair of pistons from a late (1982 I think) GS550. They are the same diameter as the GSX pistons but are 2.5mm shorter (measured but as I said the GSX pistons are rusty). I've pushed them in to the calipers and they fit well - I can't see any issues over the seals and boots and with the pads fitted I can't see them popping out..

Can anyone see any problems in fitting these.

thanks
Wally
 
hampshirehog said:
I've just bought a secondhand set of front calipers from a 1985 GSX750ES (reputedly) in good condition. They bolt straight on my GS1000 (with the GSX750 slotted discs fitted). The new calipers have got, however, completely rusted pistons which need replacing. In my pile of old and new bits I've found a new pair of pistons from a late (1982 I think) GS550. They are the same diameter as the GSX pistons but are 2.5mm shorter (measured but as I said the GSX pistons are rusty). I've pushed them in to the calipers and they fit well - I can't see any issues over the seals and boots and with the pads fitted I can't see them popping out..

Can anyone see any problems in fitting these.

thanks
Wally
Click to expand...

I cant see much of a problem with the pistons being a bit shorter but if it worries you i may have some decent condition gsx750 calipers kicking around if that helps :-D
 
Check the part numbers as they may be the same. If they are different then I wouldn't use them myself.

I know the later callipers from a 750 fit the 1000ET and later plus the 1100's.

Suzuki mad
 
Obviously, the diameter is the key thing here. I doubt if it being a few mm shorter will affect anything at all except for the amount of brake fluid behind the piston which doesn't matter much at all because it changes as the pads wear anyhow.
 
Thanks for the thoughts chaps - I also figured that it would just be a case of extra brake fluid in the chamber.

I've checked on the part numbers and they are different. I also measured the GS1000 caliper piston - it's the same diameter (to the 100th of a mm) but another 2mm shorter (so 4.5mm shorter than the GSX). Incidentally the code numbers on base of the 1000 and 550 pistons are the same - must be for the diameter?

Anyway, I've decided to give the 550 pistons a try - all slotted in fine and tested ok under pressure using a metal bar instead of pads. I'm just waiting for new pads to give it a go.

Wally
 
Yeah, it's only a little more fluid in the chamber behind the piston, but what that really means is that the pistons will pop out of the seals 2.5 (or was that 4.5) mm quicker than they should. When the lining gets low on the pads, the chances of the pistons popping out will increase. Do you really want to chance it?


.
 
The rebuild kits from Suzuki are about $15 each and include new pistons.

Why fart around with used pistons that don't exactly fit?
 
?

?

Cant believe no on has mentioned about the pistons going out of square when the pads are worn down. There is a reason the other pistons are longer.
 
I wouldn't want to fool around with brakes and if rebuild kits are only $15 and include the piston, I'd snap them up. I've done pistons on two Yammie calipers and they were $39 a piece with seal kits being another $12. seems like a bargain to do it right.

My 2 cents.
Cheers,
Spyug.
 
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