My XT brakes – will they ever perform like they used to?

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  • My XT brakes – will they ever perform like they used to?
  • cynic-al
    Member

    Sorry but spongey feeling = needs bleeding!

    packer
    Member

    I'm not sure if spongey is the right word. What I mean is once the pads have hit the disc and are gripping it tightly the lever can still be pulled back further, although it is much harder to pull.
    Is that what you would describe as "spongey"?

    tron
    Member

    Seals within the callipers. There must be some sort of seals around the pistons in there – could they be a problem. Are they user serviceable?

    There's not much room for seals to go wrong IME – they're either sealing and retracting the piston, or they're not (which is rare).

    which levers are they?

    packer
    Member

    These ones:

    Premier Icon cp
    Subscriber

    spongy does tend to indicate that there is still air in the system, and shimano brakes are renowned for being a PITA to bleed fully – it can take several attempts from what you read on here.

    It's possible you are bleading them correctly and a seal has gone somewhere allowing air to re-enter the system. There are piston seals on each of the caliper pistons and seals in the lever – it could be any of those.

    Good luck getting spare parts..!

    cynic-al
    Member

    a seal has gone somewhere allowing air to re-enter the system. There are piston seals on each of the caliper pistons and seals in the lever – it could be any of those

    As above, either seals work or they don't (i.e. fluid would be leaking etc)

    packer
    Member

    Definitely no oil leaks so I guess I can rule out the seals then.

    How about brakes hoses? Can they lose their mojo and contribute to spongeyness?

    If not I guess there must still be some air in there somewhere but god knows how I am going to get it out. The second time I bled them there were no visible air bubbles at all so I assumed I had nailed it first time.

    So would you all expect 4 year old brakes to be performing as new after a proper bleed then? Or is that unreasonable of me?

    dan1980
    Member

    I found that I needed to use a syringe to suck all the air out the system on my SLX brakes, as following the shimano instructions left me with a spongey brake.

    packer
    Member

    I found that I needed to use a syringe to suck all the air out the system on my SLX brakes

    How did you do that exactly?

    I used the offical shimano bleed kit which seems very good. It allows you to pump new fluid through the system from the caliper end so all the oil fluid and any air bubbles come out of the lever end.
    It seemed to work extremely well.

    packer
    Member

    Thanks but that video is for different brakes which have a bleed nipple on the lever.

    retro83
    Member

    How did you do that exactly?

    I used the offical shimano bleed kit which seems very good. It allows you to pump new fluid through the system from the caliper end so all the oil fluid and any air bubbles come out of the lever end.
    It seemed to work extremely well.

    Dunno how Dan does it, but I found the same thing. I did it as follows IIRC

    Do a bottom up bleed, then pull the lever to close the circuit off, then push and pull on the syringe plunger.

    In my case I had to pull pretty hard before a few bubbles popped out and finally the brakes felt firm.

    packer
    Member

    Do you mean that the bubbles popped out in the reservoir on the lever when you released the lever?

    Macavity
    Member

    There is a Shimano vid (or 2) on youtube.

    Mister P
    Member

    A trick I use is to take the lever cap off, make sure there is plenty of fluid in the reservoir and zip tie the levers back to the bar. This forces any remaining air in the fluid out.

    retro83
    Member

    packer – Member

    Do you mean that the bubbles popped out in the reservoir on the lever when you released the lever?

    No, in the syringe (still attached to the calliper)

    Wiredchops
    Member

    Hiya,
    I think one of the over-riding factors in variability in braking power is pad condition and type. Have you changed the pads type or make? Has it bedded in yet? Are they glazed or contaminated?
    The mechanical advantage of the brake remains the same, and if there isn't air in the system as you say, then system losses through hosing and component wear etc. will be minor compared to the possible variation in pad/disc friction levels.

    I find my brake power can vary quite a lot depending on conditions etc. and what I'm putting the brake through.

    packer
    Member

    I have some XT brakes on my bike and they are about 3 or 4 years old.
    As you would expect they have slowly got worse over time with the levers needing to be pulled further and further back to achieve the same stopping power.
    So they got to the point where they were both touching the bars and I decided I could no longer put it off – I would have to sort them out, which I understood to mean changing the oil and removing any air from the system.

    I've now done that and they are much better, but definitely no-where near as good as they were when I got them. They now engage much more firmly and at a much earlier point in the lever stroke, but after that I can still pull the lever back quite a lot more, which I guess you would describe as a "sponey" feel. I'm sure they were not like that when they were new.

    Yes I have done the oil change and bleed properly. In fact I have done it properly twice just to be sure. I have the official shimano bleed kit and I followed the instructions, plus read a few alternative instructions online to make sure I wasn't missing anything.
    Also the pads are new and so are the discs as I got some new wheels recently so thought I might as well put new discs on them.

    So, I have come to the only remaining conclusion which is that there must be something else in the system that is worn out or needs servicing.
    All I can think of is:
    1) Brake hoses. Do these degrade with use or over time? Could they be contributing to the spongey feel?
    2) Seals within the callipers. There must be some sort of seals around the pistons in there – could they be a problem. Are they user serviceable?

    So what do you all think?
    Any ideas or knowledge you can share on this would be appreciated.

    ro
    Member

    but… but… disc brakes are a BIG step forwards.

    surely you can cope with some minor technical issues like air in the system, hydrophilic brake fluids, pads that last less than 200k's, unnecessary system complexity (if it can fail it will, and at the most inopportune time), warped disks, grit getting stuck everywhere, frame judder, mounts that need to be faced to perfection, additional weight, blah, blah.

    but, hey, it's progress, right? and it makes your bike look like a MTX'er!

    *wanders off muttering about the Emperor's New Clothes and the general gullibility of folk*

    B.A.Nana
    Member

    My XTs are like that, used to be fantastic, until I started messing with them, now aren't as powerful, but still work ok. For example, I can't easily do endos anymore, the brakes don't bite enough. I have replaced a hose on one brake and it made no difference. My guess is that there is always a bit of air left in the system, no matter how hard I try to do it correctly. I've buggered about with them so much, both methods, top down, caliper up, that I eventually accepted a compromise. Everytime I've messed with brakes (previously Hayes Nines) I always swear next time they go straight to the LBS.

    packer
    Member

    retro83 – ah I see. Thanks – I will try this.

    Wiredchops – thanks. I am really just looking at the way the levers feel when the bike is in the workstand right now. I will get to the pads once I get it out for a ride.

    StuF
    Member

    I had a similar problem with my lx brakes. It took several goes, including sucking some of the oil out at the caliper, its possible to get some dirt stuck in there from the bleed nipple if you just squirt it in.

    try here

    packer
    Member

    ro – I hear what you are saying, but bear in mind that this is the first time in the 4 years I have owned them that I've ever done anything to them, other than slip in new pads every now and again. That is pretty impressive I think as they have performed great, and even though I am complaining about them now they are still performing better than any rim brake I ever owned.

    B.A.Nana – I feel your pain. However I refuse to believe that the LBS are going to perform any magic on the brakes that I could not do myself at home. I just need to find out exactly what that is…

    B.A.Nana
    Member

    If you look at the link from StuF, that was me who got dirt stuck in the caliper. The dust cap was missing off the bleed nipple, when I did a bottom up bleed, I pushed dirt into the caliper, it caused me no end of problems until, as a last resort, I stripped the brake down and found the dirt in the caliper. Oh happy days. 😀

    dave_rudabar
    Member

    I have a similar problem with my XTs – you'll find that if you pump the brake lever a few times it'll probably get better, indicating there is still a bit of air in there – grrr!

    wheelz
    Member

    I've just had this problem with the rear XT brakes on two of my bikes. The problem with mine was that air was still left in the caliper, despite using a syringe as described above to try and "suck" the air out.

    The only way I could bleed them properly was to take the caliper off the mount and let it hang down so the bleed nipple was at the top. Bleeding them in this position allowed the air that was lodged in the opposite end of the caliper to the bleed nipple to escape upwards through the nipple.

    Both brakes are now fine.

    adstick
    Member

    Worn rotors?

    JonR
    Member

    Sorry if this is in any way a thread hijack but is it possible that a set of brakes have pistons worn out so their performance is impared. I have a set of the newer type XTR – M975 brakes that simply don't perform as they should and yet I've bled them several times. They have had a good bit of very hard usage and I'm just wondering if they are at the end of their life? Anyone had a set that have simply worn out?

    cynic-al
    Member

    I don't see how hydraulic brakes can "wear out" if seals etc still all working.

    my guide to bleeding Shimano brakes

    Check the link here, 5th post down for my method of bleeding Shimano brakes. I recommend the bottom up method.

    packer
    Member

    adstick – nope, rotors are nearly new.

    JonR – That's sort of what I was asking in my original post. However after reading all the replies here and thinking about it a bit I think not. I think that I and anyone else in the same boat have to admit that however well we think we have bled our brakes there is still some air in there somewhere…

    tf
    Member

    2) Seals within the callipers. There must be some sort of seals around the pistons in there – could they be a problem. Are they user serviceable?

    Contrary to what was said above, caliper seals do fail, and the failure need not be catastrophic (e.g., oil spewing out in big quantities). Common cause of that is pushing the pistons back when replacing pads without thoroughly cleaning the bits of the pistons that stick out. And no, seals on Shimano calipers are not user serviceable.

    Having said that, what you describe sound lot more like the brakes are not properly bled.

    Premier Icon ahwiles
    Subscriber

    if you've bled your brakes properly, and they still don't bite, i would guess that you've got oil or similar on your pads/discs.

    it's easily done, especially if you use spray lube anywhere near your bike.

    even if you think you've been carefull, the misted oil hangs around in the air for minutes.

    Premier Icon captaindanger
    Subscriber

    JP! Can't be bothered to read all the stuff here but there are only a few things that can be wrong
    1. air in the hose, unlikely if you've bled it, I did Shay's on Sunday by injecting from the bottom, not Shimano method but it's how you do magura's, worked a treat
    2. pads/rotors contaminated, this might make you think it's a spongey feel cos it's not stopping you as quickly as you'd expect, I have managed to marginally improve mine by scrubbing everything with IPA, think you need to replace the pads though. Doesn't take much oil either, touch them a bit ith your greasy hands and it'll ruin them forever as far as I can tell.

    That's pretty much it!

    JC

    Premier Icon captaindanger
    Subscriber

    Might try putting my rotors in the dishwasher too- that gets everything clean!

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