Rear XT brake, too much flex in the lever

quannum

quannum

Likes Dirt
Hi

I’m running an M785 rear disc setup.

Squeezing the lever, it bites reasonably well, but I can keep squeezing until the lever hits the bar. All the brake adjustments are dialed back to minimum.

I’ve bled the system and I still have the same issue.

I’m reasonably sure I have the air out so, other than I haven’t and need to keep trying, are there any other reasons I can compress the lever so much?
 
teK--

teK--

Eats Squid
how old are the brakes? Maybe you have a leak in a piston seal or there is a crack in a piston.
 
G

Goats

Squid
quannum said:
Hi

I’m running an M785 rear disc setup.

Squeezing the lever, it bites reasonably well, but I can keep squeezing until the lever hits the bar. All the brake adjustments are dialed back to minimum.

I’ve bled the system and I still have the same issue.

I’m reasonably sure I have the air out so, other than I haven’t and need to keep trying, are there any other reasons I can compress the lever so much?
Click to expand...
I always have similar issues with Shimano Brakes.
After a bleed the lever is very firm with a bleed block in but lever is softer after the wheel is put back in.
Try winding the lever out to its full reach then wrap a rubber band tightly from grip to lever and leave the lever depressed overnight. Seems to reset the pistons closer to pads and should hopefully improve the feel of lever.
 
Mr Crudley

Mr Crudley

Glock in your sock
Goats said:
Try winding the lever out to its full reach then wrap a rubber band tightly from grip to lever and leave the lever depressed overnight. Seems to reset the pistons closer to pads and should hopefully improve the feel of lever.
Click to expand...
This also does wonders for S**M brakes. Recommended and does the trick.
 
k3n!f

k3n!f

leaking out the other end
I've recently been trying to fix the same issue with some 4 year old XTR brakes. A full bleed of the system with the bleed blocks and the lever still pulls in to far and feels a bit spongy.

I ended up following the "Reducing Piston Travel" tip from the video below and it seems to be working. Basically you remove the wheel, gently squeeze the lever to move the pistons in slightly, and then replace the wheel. This should draw more fluid from the reservoir into the caliper, so following this I did a "mini bleed" at the lever to top the fluid up. This will overfill the system slightly, but it feels great now so hopefully it will work!

GMBN video with the "Reducing Piston Travel" tip

Mini bleed
epicbleedsolutions.com

5 Minute Shimano Mini Bleed

Spongy Shimano brake lever? Remove air bubbles and win back great feeling brakes with the 5 Minute Shimano Mini Bleed.
epicbleedsolutions.com epicbleedsolutions.com
 
EsPeGe

EsPeGe

Likes Bikes and Dirt
When I bleed my shimanos I use an ez bleed kit which has a much thinner bleed block than the shimano one. This get the pistons much closer to the correct spacing. I also wind out the "freestroke" (should be called "complete joke") screw almost all the way out to increase the total volume by a smidge. Then after the full bleed I clean the calipers thoroughly and drop the pads back in, put the wheel on then actuate the brakes until they stop the wheel. At this point I generally find them still a little mushy for my tastes. So I drop the front wheel out much like in the video above and pull the lever all the way back to the bar once then put the wheel back in. I then put the bleed funnel with fluid in it back on to the lever and top up the fluid and confirm that all the air is definitely out. I close the bleed port up and the wind the "freestroke" screw all the way in. Bingo super solid feeling, early bite point brakes that generally feel the same on both levers.
 
Minlak

Minlak

custom titis
EsPeGe said:
When I bleed my shimanos I use an ez bleed kit which has a much thinner bleed block than the shimano one. This get the pistons much closer to the correct spacing. I also wind out the "freestroke" (should be called "complete joke") screw almost all the way out to increase the total volume by a smidge. Then after the full bleed I clean the calipers thoroughly and drop the pads back in, put the wheel on then actuate the brakes until they stop the wheel. At this point I generally find them still a little mushy for my tastes. So I drop the front wheel out much like in the video above and pull the lever all the way back to the bar once then put the wheel back in. I then put the bleed funnel with fluid in it back on to the lever and top up the fluid and confirm that all the air is definitely out. I close the bleed port up and the wind the "freestroke" screw all the way in. Bingo super solid feeling, early bite point brakes that generally feel the same on both levers.
Click to expand...
This is pretty much what I do - Only difference is I don't drop the wheel for the final fill I pull the lever in and make sure the fluid is 100% full witht he pads where they will be operating.

I was only discussing the brakes yesterday on a ride and I had never had a problem with XT brakes - I currently have 3 sets of XT 8120's and 2 I never have to touch but the E-Bike set has never been or felt right.
 
ozzybmx

ozzybmx

taking a shit with my boobs out
I have a brand new set of single piston XT M8100's here, does anyone know the real life gains to go to the dual piston M8120's ?

Will be running them on 180mm/200mm XT RT-MT800 Ice-Tech Freeza Disc Rotors.

Got an opportunity now to buy 4 piston M8120's before I fit and cut hoses on the 2 piston M8100's.
 
Minlak

Minlak

custom titis
ozzybmx said:
I have a brand new set of single piston XT M8100's here, does anyone know the real life gains to go to the dual piston M8120's ?

Will be running them on 180mm/200mm XT RT-MT800 Ice-Tech Freeza Disc Rotors.

Got an opportunity now to buy 4 piston M8120's before I fit and cut hoses on the 2 piston M8100's.
Click to expand...
14% more power is the rumour :)
I got 8120's on my Ripley and replaced my Hopes with them on my Torrent - Not comparing them to Hopes just wanted to go same same for all brakes and move away from DOT Fluid - I now also have them on my E-Bike - Usual Shimano stuff initial bite can feel harsh but I like that (makes me feel like I am stopping) - Seem quite powerful to me - stopping my fat arse and the E-Bike satisfactorily.
 
rangersac

rangersac

Medically diagnosed OMS
ozzybmx said:
I have a brand new set of single piston XT M8100's here, does anyone know the real life gains to go to the dual piston M8120's ?

Will be running them on 180mm/200mm XT RT-MT800 Ice-Tech Freeza Disc Rotors.

Got an opportunity now to buy 4 piston M8120's before I fit and cut hoses on the 2 piston M8100's.
Click to expand...
Outright power it is small gain. However my experience with Shimano dual pots is they actually have modulation unlike the single pots which are on/ ofg
 
ozzybmx

ozzybmx

taking a shit with my boobs out
Was speaking to a bloke I know, he's a big unit and was riding the XT 4 pots, reckons they are better stoppers than his last gen Saints. He is also a lifetime bike mechanic and a trials rider so knows a bit of shit about bike stuff.
He's absolutely stoked on them... got me thinking.
 
Minlak

Minlak

custom titis
ozzybmx said:
Was speaking to a bloke I know, he's a big unit and was riding the XT 4 pots, reckons they are better stoppers than his last gen Saints. He is also a lifetime bike mechanic and a trials rider so knows a bit of shit about bike stuff.
He's absolutely stoked on them... got me thinking.
Click to expand...
I won't lie if Modulation is your thing then these will not make you happy - If stopping is your thing you will be more than happy - Had some bleed issues with E-Bike ones only but sorted now seems fine - think it might have been pads were contaminated from new.
 
K

Kerplunk

Likes Bikes and Dirt
ozzybmx said:
I have a brand new set of single piston XT M8100's here, does anyone know the real life gains to go to the dual piston M8120's ?

Will be running them on 180mm/200mm XT RT-MT800 Ice-Tech Freeza Disc Rotors.

Got an opportunity now to buy 4 piston M8120's before I fit and cut hoses on the 2 piston M8100's.
Click to expand...
Imo they are a significant improvement.. (for my 95kg). They came with resin pads and they actually have a noticeable level of modulation compared to the 2 pots. I have found the initial bite less but the power comes on stronger.. Def less effort required for more braking power.
I gave them a solid hit out at Bright and no issues with wandering bite point. Can’t go wrong with them. As plenty of reviews have said, who doesn’t want more braking power?
 
K

Kerplunk

Likes Bikes and Dirt
Minlak said:
I won't lie if Modulation is your thing then these will not make you happy - If stopping is your thing you will be more than happy - Had some bleed issues with E-Bike ones only but sorted now seems fine - think it might have been pads were contaminated from new.
Click to expand...
I found the opposite, i have m785’s , m8000 2 pots and m8120’s. The 4 pots with resin pads actually have some modulation/less inital bite on my setup..
 
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