Anyone have problems with a leaky Shimano brake caliper?

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AlgaeHater
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Joined: Sun Jan 27, 2019 2:53 am

by AlgaeHater

I've run into the following problem. I took my Ultegra R8070 equipped BMC for a ride the other day and experienced a squealing rear brake along with greatly reduced stopping power. I assumed that the pads and/or rotor were contaminated so I proceeded to replace the stock resin pads with a new set and thorougly cleaned the rotor with isopropyl alcohol. The brakes seemed fine on a quick test ride. The bike sat for a few days and then on my next ride, low and behold the squealing came back. At this point, I'm guessing that the caliper itself is the culprit - the mineral oil must be seeping from the piston seal and contaminating the pads.

Is this a common problem with Shimano road calipers? Anyone else run into this issue?
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jlok
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by jlok

brake hose secured at brake caliper? is it tightened enough?
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mattr
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by mattr

Not exactly common, but fairly well known.

Unfortunately, no spare parts available, so it's either warranty or a new caliper.

AlgaeHater
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by AlgaeHater

jlok wrote:
Tue Mar 12, 2019 5:59 pm
brake hose secured at brake caliper? is it tightened enough?
Yup, I rechecked both the main brake line and the bleed nut. Both are tight.
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AlgaeHater
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by AlgaeHater

mattr wrote:
Tue Mar 12, 2019 6:00 pm
Not exactly common, but fairly well known.

Unfortunately, no spare parts available, so it's either warranty or a new caliper.
What I can't figure out is even if the piston seal is leaking, how would the mineral oil work it's way around to the pad as the piston pushes on a metal backplate. Perhaps the oil wicks around the backplate and contanimates the pad?
2019 S-Works Venge Di2
2019 Bianchi Oltre XR4 eTap
2019 BMC Timemachine Road 01 Di2
2018 BMC Roadmachine 02 Di2
2018 S-Works CruX 1X Di2

robo
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by robo

I've had this with Shimano Ultegra calipers - suggest either warranty or replace caliper unit (I went with Hope and am 100% happy with them)

TheKaiser
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by TheKaiser

AlgaeHater wrote:
Tue Mar 12, 2019 6:13 pm
mattr wrote:
Tue Mar 12, 2019 6:00 pm
Not exactly common, but fairly well known.

Unfortunately, no spare parts available, so it's either warranty or a new caliper.
What I can't figure out is even if the piston seal is leaking, how would the mineral oil work it's way around to the pad as the piston pushes on a metal backplate. Perhaps the oil wicks around the backplate and contaminates the pad?
I've seen this happen on the MTB calipers. Depending on the type of pad, the oil doesn't necessarily need to wick around the backplate, as many pads have holes in the backplate where the pad material sort of interlocks or keys in place. Pad materials are porous, and so once the oil exposed to the back side of the pad material via these holes, it can then be drawn right through the pad to the rotor contact face. That porousness is also what makes cleaning pads such a spectacularly unsuccessful effort. Occasionally I've heard of people successfully burning the oil/fluid out with a torch or something, but for the most part, once the oil is absorbed into the pad, they're throwaways.

Back to diagnosing your problem though, whenever I've seen a caliper with a leaky piston seal brought in for service, if you pull the pads and look at the backing plates there is a visibly wet ring in the shape of the piston contact surface. Since you just thoroughly cleaned yours, and probably haven't done much riding since, it may be that the oil hasn't built back up to that level, but it's something to keep in mind for the future. I'm not sure of the exact conditions that trigger the leaking, for example is it peak pressure, or rapid cycling on/off of braking force, but you could try zip tying the brake into the on position and leaving it overnight to see if you can confirm where the leak is.

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onemanpeloton
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by onemanpeloton

I'd go as far as to say it's common.

Plenty of cases of it online and I've had 2 sets of calipers do it. It's not even limited to a certain model/batch, I've seen reports of this happening with all different types of shimano calipers.

I think the leak comes past the piston seal and on to the pads.

They're cheap enough to replace (I just bought a caliper for £35 new) but on my other bike I've changed them out for Hope RX4s. The hopes dont perform any better but at least they are serviceable!
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mattr
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by mattr

onemanpeloton wrote:
Mon Mar 25, 2019 10:58 am
I'd go as far as to say it's common.
Nah, shimano sell 100s of thousands of brakes a month across the globe. Not many fail.

I've seen about 40-50 failed across 3 international forums and 4 (essentially) domestic ones.

FWIW, i've just had one go on my training bike (M7000). Just have to decide to replace like for like (probably) or buy some new hope brakes for my race bike and shuffle some kit around.

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onemanpeloton
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by onemanpeloton

mattr wrote:
Mon Mar 25, 2019 12:41 pm
onemanpeloton wrote:
Mon Mar 25, 2019 10:58 am
I'd go as far as to say it's common.
Nah, shimano sell 100s of thousands of brakes a month across the globe. Not many fail.

I've seen about 40-50 failed across 3 international forums and 4 (essentially) domestic ones.

FWIW, i've just had one go on my training bike (M7000). Just have to decide to replace like for like (probably) or buy some new hope brakes for my race bike and shuffle some kit around.
Well it isn't rare. So I'll say common
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dricked
Posts: 188
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by dricked

So the hope RX4’s only allow 160mm rotors, is there any other options for a flat mount caliper that would allow a 140mm rotor? I like the look of the hope calipers and that they’re something different than what you see on a bike rolling off the showroom floor but would prefer the smaller rotor.

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