4 year old Deore 4-pots. I have not ridden MTB for a month. It was put away hosed down and all working.
Pull it out today and there's a banshee in my brakes and very little power.
I've wiped rotors with a clean cloth. (Turned cloth black). I've sanded the pads. Full bleed and fresh fluid.
Still down on power and howling.
The other two bikes with similar Shimano brakes on, one not ridden since Christmas one a month or so too, absolutely fine.
This was a warranty set of brakes when my first pair did this at nearly a year old.
So, who's got some cheap Magura's?
Sounds very much like a leaking caliper seal.
Have you got a long drag of a road hill you can go down dragging a brake until it's smoking hot... Then do it again
That usually sorts it for me at least for a week or two.
New caliper is generally the answer.
Interestingly years ago when everyone was moaning about Shimano brakes I didn't have a single issue. The last 4 years I've had a couple of lever seals fail, three caliper seals fail and a weird road brake lever feel I'm yet to get to the bottom of.
Got to say I'll be looking elsewhere next time.
Agree with CP on this. Happened to my two pot Deores years ago and had exactly the same symptoms. Interestingly it seemed to happen after a month of not using the bike, normally it would get ridden twice a week. So not sure if the micro leak had been present for a while but regular use was enough to burn off the oil. Whereas 4 weeks of doing nothing it just bled into the pad. Try changing the pads and see if that fixes it.
Son has some Magura 4 pot calipers with Shimano levers, Shiguras. They're eyeball poppingly powerful.
Had the same, replaced pads happened again replaced caliper happened again then realised I had changed my bike cleaning liquid before the first fail. Not naming the popular product but changed and the problem disappeared. Assume I wasn’t rinsing enough or was over applying either way never had an issue since
Clean the pads with brake cleaner and then cook them in the oven, and go liberal with brake cleaner on the discs until the paper towel you are using stays white.
Had this... New rotor, new pads, worked for a few weeks then like a goose with no bite and lived with that for several months finally got round to swapping caliper, fresh fluid/bleed, thoroughly cleaned everything. Then noticed how badly I'd over-greased the shimano cup-n-cone axle/bearings. Removed rotor to thoroughly clean outer seal of hub. Brakes good but will see in a month. But because of the hub over-greasing I'm now wondering if it was that rather than leaky caliper seal. Fun!
My first ancient Deore hydros lasted ten years of regular use only needed bleeding a few times. Still get occasional use now but wouldn't do anything risky with them. Remember also seeing the shimano-brakes-hating and wondering why, until a couple of years ago.
Shimano brakes are hit and miss now unfortunately. They used to be great, now some are great, and some are awful. And it can be XT etc, not just the cheap ones.
Shame as they were the go to replacement for Avid for years.
Also their complete refusal to sell spare parts (pistons, seals etc) is infuriating.
My first ancient Deore hydros lasted ten years of regular use only needed bleeding a few times. Still get occasional use now but wouldn’t do anything risky with them. Remember also seeing the shimano-brakes-hating and wondering why, until a couple of years ago.
I was the same, had some 2 pot deore that worked for years with no maintenance, didn’t understand all the shimano hating, then had some zees which were great but got micro leaks. Wasn’t visible and spent about £40 on changing pads until I realised what was up and got them refunded under warranty.
The recent thread on hope puts me off (I’m not good with mechanics, it all goes to the lbs as I’d rather be riding), the dominions seem a faff with spares, magura look good but all I hear is the bolts and levers are made of cardboard/cheese.
Sram guide re are my typical cost effective go to’s
My deore 4 pots bought last august started doing this a couple of weeks back. Howling and poor power at the start of a ride, fine after a few decent descents.
I bought them online from merlin, Will I have to return them to merlin or can any shimano dealer do warranty? (Actually it’s only the rear that’s doing it)
I've had this on a few sets over the years. Merlin did a warranty for me on one set.
There is a thread somewhere on here about replacing the seals. You can buy stuff on eBay. Although there was speculation as to which seal was leaking? It's not the piston seals but the one between the two halves of the calliper?
It’s not the piston seals but the one between the two halves of the calliper?
I've had and seen on other's bikes both piston seal and caliper half seals fail. If it's the caliepr half seal then that can easily be replaced with a small o ring from a selection pack from Aldi (worked for me anyway!).
I've a set of 3month old code r brakes I'm making a half arsed effort to sell.
Maguras on 3 bikes just great brakes. A little faff on the bleed but once you have the technique they are spot on every time.
After having problems with several sets of Shimano (breaks), I think it's time that Shimano actually fixed the fundamental problem.
It just not reasonable for them to keep ignoring the problem. I don't want to repair a safety critical component with an random o ring or set of seals bought on Ebay.
I had the same happens to my Deore 4 pots on my full suss a couple of years ago.
I'd just bought a Hardtail and was using that for a couple of months before going back to the full suss.
Asked questions on here and all said leaking pistons. I re-bled the brakes put new pads in and after one ride is was squealing again with no power.
Ended up buying some hope tech 3 e4 and so far seem very good.
I would have stayed with Shimano if you could buy spares but you can't and have to buy a new caliper.
Happened to every single set of Shimano brakes I've ever had. At least 5 pairs.
Wont touch Shimano now. Lesson learned.
Easily fixed.. the calipers are very basic.
It's likely dirt ingress in the piston seal groove. Fully disassemble, clean groove, reassemble.
Ive got shimano calipers on one bike that must be 15 years old. They're good as gold.
Asked questions on here and all said leaking pistons. I re-bled the brakes put new pads in and after one ride is was squealing again with no power.
That won't have fixed your problem.
Its true that there are no OEM seals, but there are aftermarket spares on the bay. The ones I bought worked.
As magoos mate said above, dirt can accumulate under the seal too.
I've had this on 9 different callipers. 3 sets of XTRs 2x 988s and 1x 9020s (these are all one piece callipers) and 3x R685/785 road callipers. Once they go, nothing recovers the pads or, in my experience, the rotors. All of the replacement Hope brakes and callipers have been perfect over many years of hard abuse or sitting for long periods. It would take a lot to convince me to buy Shimano again.
Easily fixed.. the calipers are very basic.
It’s likely dirt ingress in the piston seal groove. Fully disassemble, clean groove, reassemble.
Ive got shimano calipers on one bike that must be 15 years old. They’re good as gold.
1. it's not the older brakes which give problems is seems to be everything after 775 and the 9/10 speed stuff.
2. Even if it is the seals and they're an easy fix - why does it always happen ONLY to Shimano and Only after 2011? Maybe a new seal will fix it, for a time, but the next time you go out, do you really want ambiguity in brakes?
Can you put a Hope caliper on a shimano road group Daffy? That's were it sucks the most - MTB you have a lot of choice but road / cross I much prefer a shimano drivetrain.
as gold.
1. it’s not the older brakes which give problems is seems to be everything after 775 and the 9/10 speed stuff.
2. Even if it is the seals and they’re an easy fix – why does it always happen ONLY to Shimano and Only after 2011? Maybe a new seal will fix it, for a time, but the next time you go out, do you really want ambiguity in brakes?
The caliper design of the mtb brakes is unchanged.. probably been the same twenty odd years. I've got old brakes and new ones.. the caliper is still the same.
You don't need new anything either ime.. the seals are very hard wearing and just need cleaned.
Can you put a Hope caliper on a shimano road group Daffy? That’s were it sucks the most – MTB you have a lot of choice but road / cross I much prefer a shimano drivetrain.
@Garry_Lager - Yes. RX4+ work perfectly with Shimano road levers. I’ve got 3 sets and all have been faultless for tens of thousands of km.
Yeah I'm sad to say I am now slowly moving Shimano brakes off all my bikes.
I really like the lever shape and feel when they are working, but over the long term they are proving flaky and also expensive, what with hafing to piss about with new caliper seals etc..and also bleeding without the wandering bite point is a pain.
SRAM Code RSCs on two bikes and guides on another now. I don't like the feel as much as the shimanos, but the thing is, they just work.
The caliper design of the mtb brakes is unchanged.. probably been the same twenty odd years. I’ve got old brakes and new ones.. the caliper is still the same.
Wasn’t the 775 the last that was monobloc? 785 was the first one with the different pad and newer style lever. I’ve a set of 775s that are years old and have outlasted all the newer styled shimano brakes on other bikes that have now been replaced with magura.
Even if it is the seals and they’re an easy fix – why does it always happen ONLY to Shimano and Only after 2011? Maybe a new seal will fix it, for a time, but the next time you go out, do you really want ambiguity in brakes?
because shimano brakes keep working until they don't so many people never do full bleeds.
DOT fluid forces bleeds but mineral oil just gets more and more dirt.
Sorry don't know how to quote, but I don't want to waste money on unofficial parts that may or may not work.
I ended up selling the Shimano 4 pot brakes for a decent price even though I pointed out they were leaking.
I've no problem doing maintenance work but I want to use parts that are proven especially on something as critical as brakes.
Hopefully the op can get them sorted, and have you checked the pistons aren't cracked?
If it's the inner O ring seal you can buy them for mineral oil.
I've got 5 as bought them from a bearing company in a 6 pack.
Probably leaking past the piston seal. Not past the piston but between the seal & the caliper. There's a number of design flaws. The calipers aren't anodised only painted on the outside. Corrosion starts in the seal groove & unless you remove the grot the leaks will continue. The other is that the calipers flex alarmingly when under full hydraulic pressure splaying the caliper halves apart. Don't know if the latter affects the one piece caliper bodies. The effect of this is that the pistons end up skewed in their bores.All of the two piece caliper bodies I've had apart have been corroded under the seals. I think the flexing could be partly to blame for the seal failures between the caliper halves as the seal ages and goes hard. All of this can be fixed but it's not economic unless you can do this yourself.
I’ve had and seen on other’s bikes both piston seal and caliper half seals fail. If it’s the caliepr half seal then that can easily be replaced with a small o ring from a selection pack from Aldi (worked for me anyway!).
Maybe something like a gasket sealant also.
Spread it across the machined faces of a split caliper, but more towards the leading edge at the pistons so it doesnt squeeze back and block the oil transfer hole. That might also help any seepage from migrating onto the pistons and pads.
Obviously you'd only need a tiny bit and no doubt that stuff comes in a large tin, so unless you've got another use for it it would be a bit of a waste.
Maybe see if a local garage with give you a smidgen.
This might sound a bit mad, but where do you store your bike?
I ask because after much trial end error a friend and I determined his howling brakes only became a problem after his bike was stored in his wooden shed in weather over 10°C . Above this temp the oils in the timber seemed to escape into the atmosphere and settle on his brake rotors.
My bikes living in my living room (joys of not being married!) and I've had a similar problem after frying foods with the kitchen door open and the bikes nearby.
This might sound a bit mad, but where do you store your bike?
In some cases it's definitely an environmental factor, nothing to do with seals or leakage.
Case in point; I can have a perfectly functioning, noiseless braking experience for weeks, change the wheels to a set hanging up in my garage and I have howling and lacking braking. I sort that with a good rotor clean and everything is back to normal. A few weeks later, swap the wheels back again and, bang, there's the howling. It can't be due to faulty seals as it's the non-fitted wheels that are affected, so I'm thinking that it's some airborne contamination though I can't pin down what.
I used to also have the same situation with my Fatbike. Ride it all Winter - no problem. Leave it in the garage for a few months and the first ride has howling, rubbish brakes.
The only other time I've had the issue is after having had the bike on the back of my van. Pretty sure that's exhaust and/or road contamination. Now resolved by using those Muc-Off rotor covers.
Just another data point.
Maybe something like a gasket sealant also.
The O rings are pennies... (delivery costs more).
I used a configuration tool thingy for the correct type of "rubber" (I think on a bearing co. website) where you stick in the fluid type, temp etc.
I honestly can't remember the specific type but it's worked perfectly to the point I haven't even taken it apart to check and couldn't say which caliper its even on.
I store the bike in the hallway, and for me its the rear brake. New pads or usually the fronts swopped to the rear when changing the front, and its back to working as it should, but within a couple of weeks its back to that banshee howl and no power.
I've a set of tech4 v4's here but I've been too lazy to fit them, so I could have proper brakes, but the front one works so thats really all i need(coupled with my laziness.
Brakes are the Shimano m501/m520 4pots - Good brakes incidentally.
Case in point; I can have a perfectly functioning, noiseless braking experience for weeks, change the wheels to a set hanging up in my garage and I have howling and lacking braking. I sort that with a good rotor clean and everything is back to normal.
Similarly I didn't ride my Cotic with Zees fitted for a couple of months, first ride out, horrible howling and no power. After 20 minutes of riding, it was all fine and back to normal.
An update.
I cleaned, bled and faffed with everything. Still crap.
Today I took everything off the bike. The rotors I cleaned with a household cleaner and wire wool, then I boiled in a pan of water (which turned a mucky colour..) finally put in the oven at 250*c for 15 mins.
The pads I lobbed.
The calipers I put in as hot as I could stand water and cleaned with bike degreaser and microfibre cloth. I got as much of the pistons out as I could and used cotton buds to really clean. Rinsed in really hot water a few times.
I bled off the bike, hanging hoses completely vertically and was reet fussy.
The bike is now endoing silently. 😎
I'm wondering if the calipers, which had all sorts of marks and muck on the pistons when you look closely even though I thought I had cleaned, had a bit of muck drawn in and allowing oil out under pressure. I had worn some pads right down recently, so the pistons were sticking out more than normal.
Keep your fingers crossed this week though....
Mentally prepare your self for disappointment in the morning
My ‘variable’ XT rear has been transformed by fitting a new rotor. Turns out it really didn’t like a rotor worn down to 1.1mm..
Odd one I’ve ran slx and Xt on few bikes over last 5-6 years. Been absolutely brilliant. But my Xt brake died few weeks back 🤷♂️ No idea why. Cracked piston ? Diaphragm?
Anyway bought a cheap set of Clark’s crs and so far excellent for the money 🙂
Mentally prepare your self for disappointment in the morning
I am. 😕
But, it will also prove if this is leaky something - as everything is absolutely spotlessly clean and uncontaminated...
I have a pair of 785's (road) and SLX's. The rear of the 785's started to present the leaking symptoms as outlined above. I changed the o ring mid caliper seal and the piston seals with eBay stuff and it's back to normal. Been about a year and so far, so good. The SLX's have been good as gold. They are largely ignored and rarely ridden but always A1 - so far and after about 5 years.
I bought some Hope RX4+'s which have been a bit of a dissapointment. The lever feel and braking are A1, the set up and unavoidable (in my set up) right rub have been a pain. Shame as their MTB brakes have been fantastic during my use.
had a bit of muck drawn in and allowing oil out under pressure.
Umm, I don't wish to sound snarky, but have you actually read this thread? If you have, you've not really comprehended it.
Umm, I don’t wish to sound snarky, but have you actually read this thread? If you have, you’ve not really comprehended it.
I've fully read and understood. I've had the leaky caliper seals twice before. Once on warranty, once the bin. Hence why I started the thread.
However, and with rather too much optimism, I'm keen to check if it really is duff seals, or maybe it could be that some mank has got in there or similar. It's cost me some time at present, nothing more.
If it is seal failure, I'll find out this week or so. And order Magura's...
That's a relief.
I thought we were moving to a Weeksy style thread where he asks for advice and then ignores everything suggested!
😁