Leaking Shimano Caliper?

pkovo

Well-Known Member
I have one shimano brake that keeps contaminating pads. Last time I looked for an obvious leak, didn't find one, cleaned it all up and put new pads on and was back in business. Now after a 3 month injury layoff, it's back to fractional braking power and honking like a goose.

Given the quarantine, and my lingering injury, I'll have some serious time on my hands soon once work slows, so planning to repair the entire fleet.

Anyway, for anyone that may have gone down this road before, I am wondering:

Anything obvious with the shimano calipers I should be on the lookout for when I tear this down?
Worth trying to rebuild/repair one of these, or better to just scrap and replace?

I don't want to waste my time messing with it, but at the same time I don't want to trash it if it's likely just an o-ring or something simple.


It's an XT M785 2 piston caliper. It's been in service a while, so doesn't really owe me anything at this point.
 

Aresab310

formerly RSabarese
There's a 4 page post on MTBR that may seem like what you are experiencing with the pads here:

forums.mtbr.com/brake-time/xt-xtr-brakes-get-squeal-power-loss-after-sitting-idle-6-8-weeks-902792.html

I don't normally run Shimano pads long as I prefer Truckerco. See if the thread helps you as long as you don't see any other wetness around the caliper..
 

pkovo

Well-Known Member
awesome thanks!

I didn't notice any wetness last time I went through this, but I was sort of assuming I probably contaminated them accidentally with mt grubby hands. This time I will be looking harder at everything
 

jShort

2018 Fantasy Football Toilet Bowl Lead Technician
Team MTBNJ Halter's
I had a Shimano caliper that was leaking. I just bought a new caliper. They’re pretty reasonable and easy to replace.
 

NJLuke

Member
It's my Birthday!
I have one shimano brake that keeps contaminating pads. Last time I looked for an obvious leak, didn't find one, cleaned it all up and put new pads on and was back in business. Now after a 3 month injury layoff, it's back to fractional braking power and honking like a goose.

Given the quarantine, and my lingering injury, I'll have some serious time on my hands soon once work slows, so planning to repair the entire fleet.

Anyway, for anyone that may have gone down this road before, I am wondering:

Anything obvious with the shimano calipers I should be on the lookout for when I tear this down?
Worth trying to rebuild/repair one of these, or better to just scrap and replace?

I don't want to waste my time messing with it, but at the same time I don't want to trash it if it's likely just an o-ring or something simple.


It's an XT M785 2 piston caliper. It's been in service a while, so doesn't really owe me anything at this point.
This happened to the new XTR xc brakes I have. They sat for a while and after were squeaking like geese. So 2 weeks ago I replaced pads and cleaned everything up with alcohol and its been good since then, even though I've only ridden the bike twice.
 

jdog

Shop: Halter's Cycles
Shop Keep
I have one shimano brake that keeps contaminating pads. Last time I looked for an obvious leak, didn't find one, cleaned it all up and put new pads on and was back in business. Now after a 3 month injury layoff, it's back to fractional braking power and honking like a goose.

Given the quarantine, and my lingering injury, I'll have some serious time on my hands soon once work slows, so planning to repair the entire fleet.

Anyway, for anyone that may have gone down this road before, I am wondering:

Anything obvious with the shimano calipers I should be on the lookout for when I tear this down?
Worth trying to rebuild/repair one of these, or better to just scrap and replace?

I don't want to waste my time messing with it, but at the same time I don't want to trash it if it's likely just an o-ring or something simple.


It's an XT M785 2 piston caliper. It's been in service a while, so doesn't really owe me anything at this point.
Wildly common with shimano Calipers. With a little push they often warranty the calipers. That said, shimano USA is closed in CA for the time being due to the corona virus.
 

pkovo

Well-Known Member
I could not find any sign of a leak; caliper was totally dry and still clean.

I wanted to burn the contaminants off the pads, but with my wife home 24/7 no way I could get away with tossing them in the oven. Couldn't find my torch. Probably left at in-laws when I was helping with car maintenance.

Long story short, I cleaned the rotor and sanded the pads. Seemed a good deal better but not great riding around out front. Took for a longer ride and by the end they felt pretty good.

So not sure what is going on but I think the answer is to ride it more.
 

pkovo

Well-Known Member
We are staying away from the in-laws for now. They are pretty old and hunkered down.

I rode it again tonight and it felt great!
 

Aresab310

formerly RSabarese
Yes, that's what the thread I posted above says as well, they loose power only when they sit for extended periods of time. I've had it happen to the bikes over the winter while we were using the Fatty's. Now, I buy TruckerCo pads in 4 packs ... no more issues.
 

pkovo

Well-Known Member
Yes, that's what the thread I posted above says as well, they loose power only when they sit for extended periods of time. I've had it happen to the bikes over the winter while we were using the Fatty's. Now, I buy TruckerCo pads in 4 packs ... no more issues.
Thanks....Yeah that thread was an eye opener. Made me think either a tiny leak at the o-ring between the caliper halves, or funky pads. Outcomes seemed a bit divided.

I have 5 bikes sitting in the garage with Shimano brakes ranging from basic Deore up to XT. The front brake on this bike is the only one this is happening to. That made me lean toward a leak, but who knows. Could be a bad batch of pads and bad luck on this bike I don't feel like splitting apart a well used caliper anyway. I'm going to give those truckerco pads a shot.

The last time around sanding the pads didn't seem to work, but to be fair, I only gave it a quick test, and when it didn't feel 100% I just installed new pads. I probably would have done the same this time around except since I'm quarantined, I rode it and it improved. I feel like if the pads were contaminated with fluid sanding likely wouldn't have worked.

Who knows. My plan A is truckerco pads. If it happens with them, plan B is to replace the caliper. It's lived a solid life. Plan C is fire and new bike.
 

Aresab310

formerly RSabarese
Thanks....Yeah that thread was an eye opener. Made me think either a tiny leak at the o-ring between the caliper halves, or funky pads. Outcomes seemed a bit divided.

I have 5 bikes sitting in the garage with Shimano brakes ranging from basic Deore up to XT. The front brake on this bike is the only one this is happening to. That made me lean toward a leak, but who knows. Could be a bad batch of pads and bad luck on this bike I don't feel like splitting apart a well used caliper anyway. I'm going to give those truckerco pads a shot.

The last time around sanding the pads didn't seem to work, but to be fair, I only gave it a quick test, and when it didn't feel 100% I just installed new pads. I probably would have done the same this time around except since I'm quarantined, I rode it and it improved. I feel like if the pads were contaminated with fluid sanding likely wouldn't have worked.

Who knows. My plan A is truckerco pads. If it happens with them, plan B is to replace the caliper. It's lived a solid life. Plan C is fire and new bike.
Somewhere I read that Shimano may have changed the resin compound but I can't recall where; maybe in that thread and I don't know the timing.. it could be hearsay. I have 10 or so bikes built for all of my local family in the garages and every one has Shimano hydro brakes. The ones with older pads like XT765 never had an issue but the newer XT M785 did on more than one bike when not used for months (think kids :) ). Once I switched the pads out I've gone through 2 seasons with none of the issues in that thread with a bike/brake setup that did have the issue w/ Shimano pads at one time. Meaning in my case the caliper was not leaking it was a pad issue since I only changed pads and nothing else. I didn't know what was the potential issue may have been until I read the thread since I bought aftermarket pads already, at first "Bikefridge on eBay" and then later TruckerCo. So my experiences are if your riding a bike regularly Shimano pads work just fine. When I had the issue it was resin only and not metallic.
 

Karate Monkey

Well-Known Member
Somewhere I read that Shimano may have changed the resin compound but I can't recall where; maybe in that thread and I don't know the timing.. it could be hearsay. I have 10 or so bikes built for all of my local family in the garages and every one has Shimano hydro brakes. The ones with older pads like XT765 never had an issue but the newer XT M785 did on more than one bike when not used for months (think kids :) ). Once I switched the pads out I've gone through 2 seasons with none of the issues in that thread with a bike/brake setup that did have the issue w/ Shimano pads at one time. Meaning in my case the caliper was not leaking it was a pad issue since I only changed pads and nothing else. I didn't know what was the potential issue may have been until I read the thread since I bought aftermarket pads already, at first "Bikefridge on eBay" and then later TruckerCo. So my experiences are if your riding a bike regularly Shimano pads work just fine. When I had the issue it was resin only and not metallic.
They changed the compound last year. Whether or not it was in relation to the large number of complaints with howling/squealing/low-power-braking pads that occurred in a large number of cases when a bike sat for a few weeks, we'll never know. Current pads don't seem to have the problem, but ALL of their brakes will leak from the pistons if the system is pressurized for an extended amount of time (read: days/weeks, as they were sometimes shipped, before Shimano told the bike companies to knock it off).
 

Aresab310

formerly RSabarese
They changed the compound last year. Whether or not it was in relation to the large number of complaints with howling/squealing/low-power-braking pads that occurred in a large number of cases when a bike sat for a few weeks, we'll never know. Current pads don't seem to have the problem, but ALL of their brakes will leak from the pistons if the system is pressurized for an extended amount of time (read: days/weeks, as they were sometimes shipped, before Shimano told the bike companies to knock it off).
I have had Zee, XT, SLX, Deore calipers on all of the bikes for years (some 4-5) and have never had a bit of wet at or around the caliper. All are bled firm to my liking. Most of the those bikes sit all winter when on the fatty and the fatty sits April to Oct and my experience does not mirror above. However, all of my bikes are not in a climate controlled environment as my garage is not heated and has no access from the house. So when I head out there's not a temperature difference stored vs ride. I wonder if there's something to that?
 

Karate Monkey

Well-Known Member
Assuming the brakes are bled properly, the only time they are pressurized is when the brake lever is pulled (it was fashionable to ship bikes NIB with the levers tied down to prevent movement). When you bleed the system to the top of the reservoir and close it, you might think it is pressurized, but the second you pull the brake lever, oil is advanced into the system to move the caliper pistons into their proper [initial] resting position.
 
Top