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Shimano SLX brake bleed

Francd1Francd1 Posts: 10
edited June 2013 in MTB workshop & tech
Hi, After many years cycling I figured it was really time that I learnt how to service my own bike. I started with a brake bleed and, after a few attempts I got the process working pretty well, i flushed all the fluid through, got rid of all the air bubbles and was getting a lear flow of oil out. With the bleed block in place the brakes levers are nice and firm and only require minimal depression to engage.

I replaced the pads at the same time as doing the bleed.

I've put the wheels in and the rear wheel is ok but with the bleed block out the brake feels a little spongier and needs to be depressed more to engage. The front wheel is just censored , spongy as hell and not braking at all.

I think I can explain the front wheel a little, the pads may have got contaminated so I will try replacing, however, can anyone suggest how I can firm the brakes up. I am pretty confident that there is no air in the system.

Posts

  • supersonicsupersonic Posts: 82,708 Lives Here
    Pump the brake levers repeatedly to reset the pads. If that fails, rebleed.
  • The RookieThe Rookie Posts: 27,802
    Contamination won't make the lever feel spongey!
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • Francd1Francd1 Posts: 10
    Cheers, I'm aware contamination won't make the brakes feel spongy but it would affect the braking ability, basically the front pads just don't seem to be getting any bite on the rotor.

    I have pumped the lever several times but it hasn't done any good. I'll try re bleeding but, as i say, when the bleed block is in the brakes feel perfect, when I put the pads in and the wheel they don't feel as firm and need to be pulled further back. When I first noticed the problem I rebled the system and nothing but clear fluid came out, no air at all, I've tapped the line and the calipers and I don't think there is any air in the system
  • cooldadcooldad Posts: 32,599
    What SS said - reset the pads.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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    Parktools
  • The RookieThe Rookie Posts: 27,802
    You did use the syringe first to make sure the lever was full?

    The block is wider than pads and disc so it will take a while for the pads to settle out.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • Francd1Francd1 Posts: 10
    The brakes have reservoirs so I took the top off, pulled the brake slowly, turned the bleed valve slightly, let the fluid and air out, closed the valve, released the brake, repeated numerous times keeping the reservoir topped up throughout.

    The brake firmed up nicely but once the wheels are back on it just doesn't feel as firm as I would like. As I say, the front brake pads just don't seem to be stopping the rotor at all but that could be due to contamination.

    It may sound strange but my brakes have needed doing for a while and I have forgotten how firm the levers should be, maybe I'm expecting too much.

    When you say reset the pads, what do you mean? I have reset the pistons.
  • cooldadcooldad Posts: 32,599
    This
    supersonic wrote:
    Pump the brake levers repeatedly to reset the pads. If that fails, rebleed.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • Francd1Francd1 Posts: 10
    Ah, sorry. I'll give it another go. I presume I pump the brake with the wheel back in place.

    Thanks for the help guys, normally I'd just take the bike to the shop but I feel I really should be able to do this stuff myself and now I've invested in the tools and work stand I'm bloody determined to :)
  • bonezybonezy Posts: 129
    Make sure the caliper is aligned dead square with the disc and that the pads are equal distance from the disc. If not, one pad will hit the disc just before the other. This results in the disc being bent slightly by the one pad, and that can give a mushy feel to the lever.
  • mmacavitymmacavity Posts: 781
    http://bike.shimano.com/publish/content ... _tips.html

    http://www.youtube.com/watch?v=L0oUejw5Edc

    francd1
    was there anything wrong with your brakes before you fixed them?
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    You did use the syringe first to make sure the lever was full?

    The block is wider than pads and disc so it will take a while for the pads to settle out.
    I think these are the SLX brakes derived from the XTR (something-or-other) and the XT M785s, right?
    In which case, there's no syringe used.
    There's a "hopper" kind of thing which keeps the lever (master cylinder) full during the bleed process.
  • Francd1Francd1 Posts: 10
    You're right yeehahMcgee, the levers just have a reservoir that you remove the lid of and pour the oil into.

    Mmacavity, the brakes where spongy, more so than they are now. The front brake had air in it when first bled but fluid was clear, the rear brake had bits in the oil and air.

    I dropped it into a local shop today for their advice, he said the levers weren't too bad but I could probably get them a bit firmer. I hadn't quite aligned the front caliper correctly but that actually didn't seem to make too much of a difference.

    He suggested a couple of options, rebleed again or store the bike vertically overnight with some rubber bands around the levers pulling them but not too tightly. He said it could force any remaining air into the levers but it wasn't the most ideal way of sorting the problem.

    Thanks for the links Mmacavity, I'll see if there's anything in them that might help.

    The problem is exacerbated slightly as I've changed the pads so they need to be broken in so at the moment I have next to no stopping power, hopefully they'll bed in fairly quickly.
  • supersonicsupersonic Posts: 82,708 Lives Here
    Yep, they need to bed in. Just riding it carefully, while continually pumping the levers should do it.
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    Francd1 wrote:
    You're right yeehahMcgee, the levers just have a reservoir that you remove the lid of and pour the oil into.
    Are they these brakes?
    http://www.chainreactioncycles.com/Mode ... elID=83173

    If so, I don't think you're meant to remove the reservoir cap, only the "plug" just below (or just above in the CRC picture) the lever pivot. There's then a hopper-like thing that screws into it to bleed it.
    I believe the fluid should be pretty much right up to the top of that hole, so if you're removing the silver bit with "SLX" written on it, then replacing, you're almost certainly going to have air in the system.
  • Francd1Francd1 Posts: 10
    No they aren't the same, I bought the shimano kit from CRC thinking I needed it but when I went to use the kit I realised my brakes were these http://www.google.co.uk/search?q=slx+br ... UZgbhwM%3A
  • The RookieThe Rookie Posts: 27,802
    Which one of the 2 different styles in that link?

    The older one you use a syringe only, later style the funnel and ideally a syringe prior to the syphoning as I recall.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    Francd1 wrote:
    No they aren't the same, I bought the shimano kit from CRC thinking I needed it but when I went to use the kit I realised my brakes were these http://www.google.co.uk/search?q=slx+br ... UZgbhwM%3A
    That's just a link to a google search, and since google tries to customise itself to each of us, your results may differ slightly. The first result on my list is the modern SLX, like the chainreaction link I had.
    But, like the Beginner said, there's more than one style. In fact, I'm pretty sure I'm seeing at least one image of every SLX brake ever made!!

    Oh, and this is there on your link too!!
    4979799373_21e6049ce5_z.jpg
    Which I'm 100% certain is not what you have!! :lol:
  • Francd1Francd1 Posts: 10
    Sorry guys, my fault. These are the levers http://www.sjscycles.co.uk/shimano-slx- ... prod17750/

    Having watched a couple of tutorials including this one http://www.pinkbike.com/video/170853/ and having spoken to my local bike store I'm happy with the process. The video tutorial is exactly the process i followed, just doesn't seem to be working quite as well as I'd hoped.
  • mmacavitymmacavity Posts: 781
    Proof that, the Pinkbike method does not work.

    So now time to try the Shimano recommended brake bleed method.
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    Brake bleeding can be one of those tasks where just mechanically following the steps may not result in a good bleed, it requires a little bit of art as well as science!
    (Or mechanical sympathy, as some would call it)
  • *AJ**AJ* Posts: 1,080
    Your reach adjustment was wound all the way out wasn't it?

    I find if it isn't wound out then the levers can feel spongy as they do not adjust properly. If you wind the reach adjustment all the way out, do the bleed, pump the lever a few times it will firm up and then you can wind the adjustment back in again.
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