Yup.
Shimano are notorious for poor service part availability. At least here in Australia.
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Curious what does this ring look like? My brakes work fine, but there’s sime noise. I pulled my pads out to clean today and there was some piston shaped marks but no signs of an oil leak
Noting a Shimano caliper has either five or nine moving parts - pistons, seals, bleed nipple/screw. That’s it. Taking it apart is disassembling a metal-metal interface that has to contain high pressures at high temperatures. They are tested in the factory as you’d expect. No way can you test at home.
As more brands move towards EU-mandated ‘right to repair’ adherence this may change somewhat. Some brands like PNW already have this as a mantra. I believe mfrs have an out, where if it’s safety-critical and your average bear couldn’t be expected to effect a safe repair, they can opt not to make parts / instructions available.
I believe brake calipers would/should fall into this category. A question for y’all: would any of you be happy with your partner/child riding a used bike, where the previous owner had ‘repaired’ the caliper or master piston? If you’re happy to answer ‘yes’, I’m all 
Yes, Hope have made parts available forever, and there’s a veritable cottage industry among Brit riders who have the cycling equivalent of ‘One Million Miles’ car grille badges for their Hopes. But niche of niche.
I don’t have any images on me right now, so the best I can do is this.
If you had a look at your pistons, and then see a similar shaped/sized ring of fluid (mineral oil, in this case), that’ll be it. You’d know, if you ran your finger over it. You’d be able to wipe it off the backing plate, and it’ll feel a little oily too.
Hope that helps.
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‘untested and unapproved’ - by whom?
I would buy replacement pistons, I would inspect them, and if they looked good I would install them and use them. Thus far pistons aren’t an item I’ve needed. I use after market brake pads and rotors that are not Shimano approved, chainrings that are not Shimano, and I have mixed Shimano and SRAM drivetrain components to the disapproval of both companies and worst of all I’ve used a shimano quick link more than once. I would also continue to maintain and inspect my equipment before and after use.
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By the brake system manufacturer.
3rd-party brake pads don’t need to be tested to meet local regulations - in UK anyway. Any manufacturer can rightly claim they only warranty performance using OEM parts. That said, pads and rotors are a very common aftermarket upgrade or swap - so there’s a huge body of evidence / best-practice to fall back on for both safety and liability. Some 3rd party brands are better, some worse, but it’s not like a pad 100% works and then can 100% fail under emergency braking load, which a seal inside a caliper can.
If I were sued by a customer for replacing Shimano pads with Aztec, I would have an argument to make that Aztec test their products and it’s accepted practice (unless I’d misrepresented things). If I repaired a caliper with a random kit from t’internet, I would have no body of evidence/practise to fall back on. There’s an obvious expectation that pads get replaced. There’s an explicit inference if not actual statement somewhere that Shimano calipers should not be repaired - because they don’t provide parts or instructions.
Shades of grey mixing drivetrain components compared to a caliper repair kit. Shimano don’t sell narrow-wide rings for Bosch for eg but again you could argue using a SRAM ring with an 11s Shimano chain is perfectly acceptable and proven to be safe/work).
Again I ask - would you be happy driving your kids in a car with brakes that had been repaired using unapproved/tested parts when your car mfr had explicitly said not to? If someone purchased your car, would you tell them you had made that repair yourself?
Hi John, here is that Geek warning article that talked about the issue that shimano has with it’s leaky calipers. Well worth a listen.
Episode 95. Gravel things go road and fixing easy rattles.
1:12:30 - Squealing Shimano brakes strike again.
“It is common, its something shimano hasn’t widely acknowledged”.
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Pistons might look ok, but it only takes a very small manufacturing tolerance issue or mishandling to result in a leak or complete loss of fluid pressure.
And what about the seals? How do you know if the replacement seals are of the correct rubber to not be degraded by the brake oil, and have the same potential for manufacturing tolerance issues that would not be picked up on through visual inspection.
If keeping original seals, how do you know they are still ok? Maybe it’s the seal that’s caused the original problem?
I have thought about trying such piston kits, but decided against it as nothing has been done to justify having any trust in the product. Can you pin down the brand in any way that gives you any confidence that you could make any warranty claim?
The opposite of that would be Hope or similar aftermarket brake manufacturer, who design their brakes to be serviced and supply parts to allow it. They are contactable, have good customer service and good track record, justifying trust in the products and service parts.
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Thank you. For reasons I can’t explain, I can’t access the MO podcast for this… I only seem to be able to find the free one. But thanks.
Ah… never mind. Describes my problem exactly, other than the lack of use. Interesting…
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Sram, Hope, Tektro, Trickstuff all offer pistons and rebuild kits. Shimano not offering pistons is an indicator that they consider their brakes to be disposable, so the logic is that these other brands consider their brakes to be repairable?
I think that’s consistent Shimano’s other design choices too.
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I just want to go back to the warranty question. Are you contacting Shimano, or is your bike shop? I just had a pair of 6100 calipers replaced after 4-ish years. As far is know, they didn’t give the shop any trouble.
The bike shop on my behalf. They were meeting with their Shimano rep last week. I have not followed up. Too busy rehabbing from a heart ablation.
I went through multiple front R8070 calipers that did this. Riding regularly it would be a weak enough leak that it didn’t do anything, but if I took more than a week or two off or sprayed the brake too closely with a hose when washing the bike it would squeal after and the pads would be toast. Now I’m on a R8170 bike and dont have the problem, so would definitely recommend the upgrade if cost isn’t an issue.
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I’ve just ordered a new 8070 rear caliper. I’m tired of have weak and noisy rear brakes. Interestingly, when I asked my local shop (Aus) about ordering one, they reckoned there was none in stock with the distributor and potentially couldn’t be back ordered. Has Shimano stopped supplying these now?
I’ve not seen the older caliper available for a while not at my (UK) Shimano distributor. There really is no need either as the 8170 is a much better option and works perfectly with the older brakes.
Interesting, does it change lever feel due to servo wave and extra clearance?
I just replaced my 8070 calipers with GRX820 (which I think is pretty much the same as 8170?) and its working great with my 8020 shifters. I run a pretty tight ship so no issues with clearance before or now. The 8070 calipers developed a leak.
Lever feel is the same. My LBS did the change but I imagine the feel is more dependent on how you bleed the brakes.
I believe servo wave is a feature on the levers not the calipers.
From my experience having fitted many of new Shimano calipers to older levers , no.
My almost daily commuter bike also has a mixed setup with Ultegra 8020 levers and 105 7170 calipers. 1000s of miles, no issues at all.