ST1100 Rear brake caliper piston

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Attached is a photo of one of my ST1100 rear caliper pistons. I used pliers to pull it out of the caliper, which it appears may not have been a great idea. You can see it's little rough in the place where the pliers gripped it. My question is, is it history and I have to buy new one?

Thanks in advance for your help.

Colin
 

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Andrew Shadow

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You have posted this in the ST1300 section of the forum. There are many ST1100 owners on this forum who never look at the ST1300 threads so they will not see your question. You should re-post this in the ST1100 section or ask a moderator to move it for you.

If the the piston never needs to be retracted in to the caliper far enough for the dust seal or the o-ring to contact this area of the piston you can get away with it. From the picture I doubt that however. I am sure that with a new set of brake pads you would need to retract the piston so that the seals will contact this area and then you are risking damage to the seals. From the picture I don't think that you would be able to polish it out enough to save it. I would replace the piston.
 

jfheath

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I wouldn't want that in my brakes. The marks from the pliers would allow fluid to seep past and probably rip the seals to shreds. Result - no brakes.

The only consolation might be that it looks like there was pitting and corrosion on the surface - which would have meant replacing it anyway. It's only 30 CAD (ish).

For future reference - there are tools that grip on the inside of the piston to remove them - not that I have ever used one, so I can't advise. Compressed air is excellent - but needs the fluid to be removed first and a bag in which to catch the flying projectile.

If you don't have access, then the best bet is to use the power of the brake system itself and slowly pump the pistons out. It's possible that one will come out faster than the other (in twin piston units, or the outer psitons in a 3 piston system) - if so, engineer it so that the reluctant one gets pushed out, preventing the first one from moving until they are both moving out together. One will pop out first, leaving the other to be removed by hand, but this way you are not left trying to get the more difficult one out by hand, and it will be close to dropping out anyway.
 

ReSTored

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Shot, has to be replaced.

US $$ cost from Partsfish last time I ordered.

SEAL SET, PISTON 06431-MA3-405 $4.42 X 2 $8.84
PAD REAR BRAKES 06435-MT3-405 $33.51 1 $33.51
PIN HANGER, REAR 45215-HE0-016 $5.73 1 $5.73
PISTON 45107-ML4-006 $22.02 2 $44.04
 

ReSTored

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........... use the power of the brake system itself and slowly pump the pistons out. It's possible that one will come out faster than the other (in twin piston units, or the outer psitons in a 3 piston system) - if so, engineer it so that the reluctant one gets pushed out, preventing the first one from moving until they are both moving out together. One will pop out first, leaving the other to be removed by hand, but this way you are not left trying to get the more difficult one out by hand, and it will be close to dropping out anyway.
This is how I do it. I use a small piece of plywood to prevent the looser piston from popping out before the tighter one gets pumped out.
 
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