Shimano Piston partially broken
06-24-19, 10:58 PM
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Shimano Piston partially broken
https://i.imgur.com/zwMHADV.jpg
The right piston of my front Shimano BR-RS805 would not fully reset flush. Took it apart to find the ceramic pieces crumbling internally. No wonder it would not push in much further. Took out the debris and cleaned it up. Since it was only breaking apart one side I temporarily reversed the piston so at least I have a semi functional brake to use.
Where can I get replacement pistons?
The right piston of my front Shimano BR-RS805 would not fully reset flush. Took it apart to find the ceramic pieces crumbling internally. No wonder it would not push in much further. Took out the debris and cleaned it up. Since it was only breaking apart one side I temporarily reversed the piston so at least I have a semi functional brake to use.
Where can I get replacement pistons?
06-25-19, 06:44 AM
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Thanks for providing the part number it makes searching ("Shimano BR-RS805 ev pdf") easier. This document does not show the pistons as separate parts: :-(
https://si.shimano.com/pdfs/ev/EV-BR-RS805-3852A.pdf
https://si.shimano.com/pdfs/ev/EV-BR-RS805-3852A.pdf
06-25-19, 09:37 AM
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Ebay lists a few aftermarket aluminum pistons from China. https://www.ebay.com/sch/i.html?_fro...RS805&_sacat=0 Looks like various shimano calipers use the same size pistons if you happen to come across some listed for other models.
06-25-19, 11:15 AM
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Wondering how you did that, and would be going for a warranty claim (after you have put it back together and it looks like it has never been apart) and under 2 years old.
If you of warranty would just replace with a new one, rather than fit unknown parts to a critical component.
If you of warranty would just replace with a new one, rather than fit unknown parts to a critical component.
06-25-19, 12:42 PM
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Wondering how you did that, and would be going for a warranty claim (after you have put it back together and it looks like it has never been apart) and under 2 years old.
If you of warranty would just replace with a new one, rather than fit unknown parts to a critical component.
If you of warranty would just replace with a new one, rather than fit unknown parts to a critical component.
06-25-19, 03:19 PM
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If it helps, you can find replacement RS805 calipers for around $45. I just saw some at Competitive Cyclist. Rebuildability has never been high on Shimano's priority list (most famously seen in their STI levers).
I'd also be interested in how that damage happened since I have some very similar R8070 calipers on one bike. Maybe the pistons got pushed in too far during a previous pad replacement and got crushed against the alloy shell?
I'd also be interested in how that damage happened since I have some very similar R8070 calipers on one bike. Maybe the pistons got pushed in too far during a previous pad replacement and got crushed against the alloy shell?
06-25-19, 04:39 PM
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Yes, I would agree somewhat but they can't be much worse than the pistons that shattered. I'm getting the impression that this is not an unusual problem with the Shimano calipers since I've seen this mentioned a couple times before elsewhere and the fact that there are some aftermarket pistons available. Contact Shimano with this issue and see what they say. They may offer to replace for free and they should as this is a potentially deadly problem.
Last edited by Crankycrank; 06-25-19 at 04:43 PM.
06-25-19, 04:52 PM
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Wondering how you did that, and would be going for a warranty claim (after you have put it back together and it looks like it has never been apart) and under 2 years old.
If you of warranty would just replace with a new one, rather than fit unknown parts to a critical component.
If you of warranty would just replace with a new one, rather than fit unknown parts to a critical component.
When I bought the new bike the piston never really fully reset, but close enough it still worked so I shrugged it off. Problem probably already started then. As time went by it got worse probably due to more pieces inside chipping. Wasn't able use it anymore as I couldn't put the wheel back on.
Last edited by Hisamatsu; 06-25-19 at 05:04 PM.
06-27-19, 02:31 PM
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Went to my LBS to see if they had the same brake caliper to replace and quoted me $98 special order. I'm going to give the $10 aftermarket piston.
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