Why are my brakes pants?
Discussion
I'm having a bit of trouble with how the brakes on my MTB perform, bearing in mind I'm not hammering them down trails and I'm pretty much a fair weather rider, they're just not working anywhere near as well as I feel they should.
Bike is a Cube Acid 27.5 with Shimano A-M506 hydraulic discs, 180mm front, 160mm rear.
The front isn't too bad but the rear you can pull the lever all the way in and it's impossible to lock the wheel (I know that's not what you want anyway but it means I'm not getting 100% braking power ever)
I'm using standard Shimano resin pads front and rear and the bike is 4.5 years old, I bought it new, there's no fluid leaks that I can see and it doesn't look like there ever have been.
Any idea what the problem could be?
Bike is a Cube Acid 27.5 with Shimano A-M506 hydraulic discs, 180mm front, 160mm rear.
The front isn't too bad but the rear you can pull the lever all the way in and it's impossible to lock the wheel (I know that's not what you want anyway but it means I'm not getting 100% braking power ever)
I'm using standard Shimano resin pads front and rear and the bike is 4.5 years old, I bought it new, there's no fluid leaks that I can see and it doesn't look like there ever have been.
Any idea what the problem could be?
Fluid change and new pads I reckon.
I've gone through a set of pads in a year on a MTB no problem, about 1k miles of fairly flat trails will easily see a set off. Last rear pair I changed out were down to the metal and making some pretty hideous noises.
Easy job to bleed through, you push the fluid through from the caliper up to the lever, plastic syringe attached each end.
I've gone through a set of pads in a year on a MTB no problem, about 1k miles of fairly flat trails will easily see a set off. Last rear pair I changed out were down to the metal and making some pretty hideous noises.
Easy job to bleed through, you push the fluid through from the caliper up to the lever, plastic syringe attached each end.
You can buy a third party bleed kit which has the fluid (mineral oil for Shimano brakes) and tools / bits:
https://www.epicbleedsolutions.com/products/bleed-...
You might need some extra fluid if you want to do both brakes.
https://www.epicbleedsolutions.com/products/bleed-...
You might need some extra fluid if you want to do both brakes.
Cardinal Hips said:
Fluid change and new pads I reckon.
I've gone through a set of pads in a year on a MTB no problem, about 1k miles of fairly flat trails will easily see a set off. Last rear pair I changed out were down to the metal and making some pretty hideous noises.
Easy job to bleed through, you push the fluid through from the caliper up to the lever, plastic syringe attached each end.
I don't think I've done 1k miles in total since I've owned it and it's had a couple of sets of pads (they were noisy so I tried a new set autumn last year)I've gone through a set of pads in a year on a MTB no problem, about 1k miles of fairly flat trails will easily see a set off. Last rear pair I changed out were down to the metal and making some pretty hideous noises.
Easy job to bleed through, you push the fluid through from the caliper up to the lever, plastic syringe attached each end.
I'll get a fluid bleed kit and give it a go then.
Harpoon said:
You can buy a third party bleed kit which has the fluid (mineral oil for Shimano brakes) and tools / bits:
https://www.epicbleedsolutions.com/products/bleed-...
You might need some extra fluid if you want to do both brakes.
Perfect, I'll give that a go then, thanks for the link.https://www.epicbleedsolutions.com/products/bleed-...
You might need some extra fluid if you want to do both brakes.
do they squeal as well?
I had similar issues with the same Shimanos at a similar age - the seals on the rear were leaking ever so slightly.. this would lead to contamination of the pads, so cleaning / sanding the pads was a waste of time too.
In the end I swapped them for a better spec set off ebay that someone was upgrading.
I had similar issues with the same Shimanos at a similar age - the seals on the rear were leaking ever so slightly.. this would lead to contamination of the pads, so cleaning / sanding the pads was a waste of time too.
In the end I swapped them for a better spec set off ebay that someone was upgrading.
Steamer said:
do they squeal as well?
I had similar issues with the same Shimanos at a similar age - the seals on the rear were leaking ever so slightly.. this would lead to contamination of the pads, so cleaning / sanding the pads was a waste of time too.
In the end I swapped them for a better spec set off ebay that someone was upgrading.
They have made noise in the past, I’ll check the calipers over when I get a chance, thanks for the tip.I had similar issues with the same Shimanos at a similar age - the seals on the rear were leaking ever so slightly.. this would lead to contamination of the pads, so cleaning / sanding the pads was a waste of time too.
In the end I swapped them for a better spec set off ebay that someone was upgrading.
Again I wouldn’t have thought so, I’ve tried new pads before and it’s not been any different. Bike gets cleaned with water and a cloth (I don’t get it muddy, I don’t enjoy that kind of riding) so no chemicals, other than some chain lube but it’s not only the rear brake, the front is crap too.
lufbramatt said:
I know a few guys that have had issues with Shimano disc brakes. It almost appears like the calipers are disposable once the seals start leaking as you can't get the parts to rebuild them.
Hopefully it won't be this, I'll be even more out of my depth if I need to upgrade, I'll have no idea that I'll need to buy to fit my bike, the whole thing confuses me and I'd probably end up buying totally the wrong stuff.Bleed kit arrived today, will give that a go on Sunday and see if it works.
It didn't go well...
I did the bleed on it, top to bottom first to flush the fluid then bottom to top to get the bubbles out, used about half a litre of fluid in total!
Feels exactly the same, there's no bite at all from the rear and the front one isn't much better.
I went for a short ride, came back, cleaned the rotors and the pads, re-assembled and again, no better, came back, stripped everything down again, tried some other pads I'd got after cleaning the rotors again... still the same.
After all this I did notice there was a slight bit of moisture between the reservoir and the cap on both levers when they have pressure on them but not enough to force a drip of fluid out and it could be from the bleed process if I spilt a drop of fluid.
Googling shows Shimano don't sell a seal for the reservoir (no surprise there) so that's not something I can try.
So what do I do now? Upgrade stuff? Learn to tuck and roll at the bottom of hills? Set fire to everything?
I did the bleed on it, top to bottom first to flush the fluid then bottom to top to get the bubbles out, used about half a litre of fluid in total!
Feels exactly the same, there's no bite at all from the rear and the front one isn't much better.
I went for a short ride, came back, cleaned the rotors and the pads, re-assembled and again, no better, came back, stripped everything down again, tried some other pads I'd got after cleaning the rotors again... still the same.
After all this I did notice there was a slight bit of moisture between the reservoir and the cap on both levers when they have pressure on them but not enough to force a drip of fluid out and it could be from the bleed process if I spilt a drop of fluid.
Googling shows Shimano don't sell a seal for the reservoir (no surprise there) so that's not something I can try.
So what do I do now? Upgrade stuff? Learn to tuck and roll at the bottom of hills? Set fire to everything?
Robmarriott said:
It didn't go well...
I did the bleed on it, top to bottom first to flush the fluid then bottom to top to get the bubbles out, used about half a litre of fluid in total!
Feels exactly the same, there's no bite at all from the rear and the front one isn't much better.
I went for a short ride, came back, cleaned the rotors and the pads, re-assembled and again, no better, came back, stripped everything down again, tried some other pads I'd got after cleaning the rotors again... still the same.
After all this I did notice there was a slight bit of moisture between the reservoir and the cap on both levers when they have pressure on them but not enough to force a drip of fluid out and it could be from the bleed process if I spilt a drop of fluid.
Googling shows Shimano don't sell a seal for the reservoir (no surprise there) so that's not something I can try.
So what do I do now? Upgrade stuff? Learn to tuck and roll at the bottom of hills? Set fire to everything?
Half a litre of fluid used in bleeding them says to me you did something wrong - you should be using no more than 20-30cc's an end.I did the bleed on it, top to bottom first to flush the fluid then bottom to top to get the bubbles out, used about half a litre of fluid in total!
Feels exactly the same, there's no bite at all from the rear and the front one isn't much better.
I went for a short ride, came back, cleaned the rotors and the pads, re-assembled and again, no better, came back, stripped everything down again, tried some other pads I'd got after cleaning the rotors again... still the same.
After all this I did notice there was a slight bit of moisture between the reservoir and the cap on both levers when they have pressure on them but not enough to force a drip of fluid out and it could be from the bleed process if I spilt a drop of fluid.
Googling shows Shimano don't sell a seal for the reservoir (no surprise there) so that's not something I can try.
So what do I do now? Upgrade stuff? Learn to tuck and roll at the bottom of hills? Set fire to everything?
On thing I found on my similar generation XT brakes is that you basically have to overpressurise them when bleeding - get to no air coming out, close the bleed valve, put the reservoir cap back on, then reopen the bleed valve and give the syringe another squeeze, then close the bleed valve again.
Robmarriott said:
Steamer said:
do they squeal as well?
I had similar issues with the same Shimanos at a similar age - the seals on the rear were leaking ever so slightly.. this would lead to contamination of the pads, so cleaning / sanding the pads was a waste of time too.
In the end I swapped them for a better spec set off ebay that someone was upgrading.
They have made noise in the past, I’ll check the calipers over when I get a chance, thanks for the tip.I had similar issues with the same Shimanos at a similar age - the seals on the rear were leaking ever so slightly.. this would lead to contamination of the pads, so cleaning / sanding the pads was a waste of time too.
In the end I swapped them for a better spec set off ebay that someone was upgrading.
As another poster mentioned - the one bike I have that has the Deores on: if it doesnt get ridden for a few weeks - it will take a few miles of 'standing on the brakes' while going down sharp hills to bring them back to life...
...However, the 'squealing' sound I mentioned (and thought you might have too) is not just from noisy pads - its actually the rear pad/caliper slipping slightly on the rotor, because the pistons might be leaking slightly and thus the brakes start to lack performance.
The XT's I have on another bike feel great straight away - however a strange querk of these seems to be the massive amount of noise / squeal they make in the wet (it is a different squeal to the failing Deores though)
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