XT M8000 Brake - no power

FatMuz

FatMuz

Likes Dirt
I bought a set of new XT M8000 brakes off a Rotorburner a week or 2 ago. The rear brake feels quite soft and lacks any stopping power.
I've bled them twice now and changed the pads from resin ones to new sintered ones... and it still lacks enough power to pull the bike up, even on damp grass I can't get the rear wheel to lock up.
Help needed...Anyone got some advice or tips?

Cheers
Muz
 
Ky1e

Ky1e

Likes Bikes and Dirt
Possible contamination. Some emery paper on the rotors and pads should clear it up if contaminated
 
C

creaky

XMAS Plumper
When you say it feels quite soft, do you mean the lever is spongy ? If so, it's got to be air or a dodgy seal.
 
moorey

moorey

call me Mia
Ky1e said:
Possible contamination. Some emery paper on the rotors and pads should clear it up if contaminated
Click to expand...
Hell no. Wash rotors in hot soapy water then rinse. Cook the pads. If spongy, will also need a bleed.
 
Ky1e

Ky1e

Likes Bikes and Dirt
moorey said:
Sand the pads back to metal and you might remove the soaked in contamination....
Click to expand...
All I know is moorey I have not had one single issue with brake fade in over 2 years, resin pads, metal pads, m785, m8000, slx. But that's cool. Whatever.
 
A

allroundgoodguy

Squid
Muz

When you say bleed, did you do a complete flush, I had a similar problem with my XT's, A simple bleed didn't work but doing a complete fluid change worked a treat, The old fluid was very gungy and discoloured
 
moorey

moorey

call me Mia
Ky1e said:
All I know is moorey I have not had one single issue with brake fade in over 2 years, resin pads, metal pads, m785, m8000, slx. But that's cool. Whatever.
Click to expand...
I'm sure you haven't...as I don't reckon you've had a proper contamination like this sounds. Shimano' good like that... :woot:
 
Flow-Rider

Flow-Rider

Burner
It could be a combination of things, I would try and re-bed the pads in first. Roughen the rotors and pads with course grit sandpaper and try not to overheat the brakes on the run in period. With sinted brake pads, it normally takes me about seven brake applications in the yard at highish speeds and I can start to lock the brakes up.
 
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S

skinnybeans

Likes Dirt
As people have kind of alluded to you are describing 2 possibly seperate problems:

1. Brake leaver spongy

2. No stopping power

If your lever is spongy there's no point fucking around with the pads and rotors, because the problem is going to be with air in the lines or seals.

If you get the lever feel sorted out so its solid and you still have no braking power the proceed to pad/rotor treatment.
 
stirk

stirk

Burner
Thinking completely left field, are you running a mount for a 203mm rotor but have a 180mm rotor installed on bike?

Yeah I hear everyone laugh but stranger things get you into the fuckwit thread!
 
The Duckmeister

The Duckmeister

Has a juicy midrange
skinnybeans said:
As people have kind of alluded to you are describing 2 possibly seperate problems:

1. Brake leaver spongy

2. No stopping power

If your lever is spongy there's no point fucking around with the pads and rotors, because the problem is going to be with air in the lines or seals.

If you get the lever feel sorted out so its solid and you still have no braking power the proceed to pad/rotor treatment.
Click to expand...
This is on the money.

If the lever is soft, bleed the brake properly to get the air out of the line.

If the lever feel is solid but there's little or no friction, which is common with new metal pads, give the pads a good scuff with some sandpaper. Leave the brake dust on the pad surface, 'cos you'll need to embed this into the rotor surface.

DO NOT clean the rotors unless you can actually see oil covering the surface!!!! Continual cleaning strips the layer of embedded pad material, which is essential for proper brake performance, from the rotor surface, preventing the brake from generating full power.
 
S

schred

Likes Bikes and Dirt
The Duckmeister said:
This is on the money.

If the lever is soft, bleed the brake properly to get the air out of the line.

If the lever feel is solid but there's little or no friction, which is common with new metal pads, give the pads a good scuff with some sandpaper. Leave the brake dust on the pad surface, 'cos you'll need to embed this into the rotor surface.

DO NOT clean the rotors unless you can actually see oil covering the surface!!!! Continual cleaning strips the layer of embedded pad material, which is essential for proper brake performance, from the rotor surface, preventing the brake from generating full power.
Click to expand...
Mr Duckmeister, following from this may I please ask you your view of Muc-off cleaning product applied liberally to all things bike, including rotors/calipers?
 
The Duckmeister

The Duckmeister

Has a juicy midrange
It's fine. While great at cleaning general dirt, it doesn't have the aggressiveness to strip ground-in brake material. :smile:
 
Dozer

Dozer

Heavy machinery.
Staff member
It needs to be bled properly as others have said, that may mean doing it a few times and using some of the methods and tricks not outlined in Shimano manuals etc.

As far as Shimano goes, if you ride anything that points down and you are of a manly shape over 90kg then anything Shimano under quad piston is junk. In fact, of the six sets of Shimano brakes I've used over the years I can safely say that I would not put any of them on a bike that is ridden on a gravity fed trail or going over 30km as they don't stop good enough and "the pedal goes to the floor" too easily.
 
JTmofo

JTmofo

XC Enthusiast
Dozer said:
It needs to be bled properly as others have said, that may mean doing it a few times and using some of the methods and tricks not outlined in Shimano manuals etc.

As far as Shimano goes, if you ride anything that points down and you are of a manly shape over 90kg then anything Shimano under quad piston is junk. In fact, of the six sets of Shimano brakes I've used over the years I can safely say that I would not put any of them on a bike that is ridden on a gravity fed trail or going over 30km as they don't stop good enough and "the pedal goes to the floor" too easily.
Click to expand...
Hope E4/V4/M4........ Close thread
 
W

will2

Likes Dirt
Dozer said:
It needs to be bled properly as others have said, that may mean doing it a few times and using some of the methods and tricks not outlined in Shimano manuals etc.

As far as Shimano goes, if you ride anything that points down and you are of a manly shape over 90kg then anything Shimano under quad piston is junk. In fact, of the six sets of Shimano brakes I've used over the years I can safely say that I would not put any of them on a bike that is ridden on a gravity fed trail or going over 30km as they don't stop good enough and "the pedal goes to the floor" too easily.
Click to expand...
Gee, that's bold.
 
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