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Time for a new caliper?

reaperactualreaperactual Posts: 895
edited October 2020 in MTB workshop & tech
After a few issues with my SLX M7000 rear caliper, most recently one or the other pistons sticking. Done the usual clean up and dripping some mineral fluid onto extended piston edges which worked for a short period of time then starts sticking again. Maybe this is to be expected as brake is two years old now?

I'm reluctantly thinking about fitting a new SLX M7100 caliper. Seen a couple of good deals on a replacement but is there anything else to try first?

Is it worth splitting the caliper open to see if there could be an obvious problem with the seals or whether a good clean inside could help? Not tried this before so not sure if it's worthwhile.

Should I buy a new caliper first as a back up as not sure if the problem is fixable in the end? Don't like the look of the cheap replaceable alloy pistons I've seen on eBay but maybe someone has fitted them and fixed a similar issue?

Not found any useful user reviews on the M7100's and wondered if anyone has them and how they have performed?

Any suggestions, thoughts or feedback on the best course of action and review of M7100 would be appreciated.

Posts

  • mully79mully79 Posts: 308
    edited October 2020
    i had problems with my rear deore calliper constantly squealing so i suspected slight fluid leak past the seals.
    I split the calliper and removed the pistons and seals. There was a large amount of gunk dried into the seals and pistons. The pistons didnt look great near the pads but after a thorough clean and rebuild ive had no problems with squealing or sticking.
  • reaperactualreaperactual Posts: 895
    edited October 2020
    mully79 said:

    i had problems with my rear deore calliper constantly squealing so i suspected slight fluid leak past the seals.
    I split the calliper and removed the pistons and seals. There was a large amount of gunk dried into the seals and pistons. The pistons didnt look great near the pads but after a thorough clean and rebuild ive had no problems with squealing or sticking.

    Thanks for the reply mully79. Good to hear it's worth while trying to revive my caliper and looking forward to giving it a go. Have had some squealing but I've checked and no leaks either.

    Watched some related You Tube vids on changing calipers and replacing pistons, looks like the banjo bolt (M4) and a torx bolt holding them together, reckon they are the same size as Deore calipers but don't know what size torx key I need? 🤔

    The pistons are ceramic and not sure how to get them out safely without causing damage as not seen how it's done on You Tube clips? 🤔
  • mully79mully79 Posts: 308
    Getting the pistons out is a bit of a pig. Of course i split the calliper first and lost the chance to push them out naturally with the brake lever/fluid then stuggled for ages !
    You want to get them out as far as you can safely without losing fluid. Then hold the one on the bleed nipple side still so it cant move and use the brake lever to pop out the otherside. (warning its messy as fluid will then escape and theres no going back).
    once other side is out split the caliper. clamp something over the little oil hole to block the port to the other side (or maybe stick some tape over the hole and retighten the halves together so the oil no longer reaches the side with no piston. if youre lucky use whats left of your fluid to push the other piston out. Alternatively i rigged an air pipe onto the bleed nipple and pushed it out with my pump.(of course, be careful, wrap a towel around it in case it fires out and wear safety glasses.) it took at least 70 psi to get mine out.

    someone who actually knows what theyre doing probably has a proper way !
  • reaperactualreaperactual Posts: 895
    edited October 2020
    mully79 said:

    Getting the pistons out is a bit of a pig. Of course i split the calliper first and lost the chance to push them out naturally with the brake lever/fluid then stuggled for ages !
    You want to get them out as far as you can safely without losing fluid. Then hold the one on the bleed nipple side still so it cant move and use the brake lever to pop out the otherside. (warning its messy as fluid will then escape and theres no going back).
    once other side is out split the caliper. clamp something over the little oil hole to block the port to the other side (or maybe stick some tape over the hole and retighten the halves together so the oil no longer reaches the side with no piston. if youre lucky use whats left of your fluid to push the other piston out. Alternatively i rigged an air pipe onto the bleed nipple and pushed it out with my pump.(of course, be careful, wrap a towel around it in case it fires out and wear safety glasses.) it took at least 70 psi to get mine out.

    someone who actually knows what theyre doing probably has a proper way !

    Had a suspicion you were going to suggest the messy option. I was falsely hoping there was a better way. I suppose there isn't realistically any alternative way to do it, if there is I don't know it either.

    I'll leave it attached, try and unstick the outboard piston (non bleed nipple side) as a first step but it seems pretty stuck this time.

    Luckily I have the correct T30 Torx bit with my torque wrench set and glad I just stocked up on Shimano fluid!

    Probably going to buy a new M7100 caliper as it's a good price and will keep me on the road. Hopefully fix the this one and use for a spare, reckon the front caliper could end up sticking too with all the muddy rides coming.

    Thanks mully79. 😎👍

  • reaperactualreaperactual Posts: 895
    edited October 2020
    About to order this M7100 caliper, never bought one on its own and unattached. Can anyone confirm this is how a caliper would be supplied and more importantly if the part arrowed (banjo bolt?) would be included?






  • mully79mully79 Posts: 308
    I havent bought a caliper seperately so sorry I couldnt say.
    The part is called a banjo bolt if you want to search for it seperately or check in description.
  • mully79mully79 Posts: 308
    Oh and i think I got confused. The fluid line and bleed nipple are on opposite sides so if you do it my way you'd have to use compressed air/pump to push out the piston on the bleed side.
    if a piston is jammed and tilted its usually better to straighten it by pushing it all the way back in before trying to get it out.
  • steve_sordysteve_sordy Posts: 2,239
    If you can get the pistons to move, you are in with a chance!
    I have Shimano BR M520 (4 pot). One of the pistons cracked and jammed in, even the LBS couldn't get it out. That was a new rear calliper under warranty. The front calliper has had both pistons on one side jamming. The LBS struggled to shift them but did manage to free them off in the end. I have had intermittent problems with both brakes. I have to keep doing mini bleeds or adjusting the position of the calliper body. When they work, they work really well. But I am used to having Shimano brakes (SLX or XT)working well and faultlessly for years and years. Have Shimano gone too cheap?
  • reaperactualreaperactual Posts: 895
    edited October 2020
    mully79 said:

    I havent bought a caliper seperately so sorry I couldnt say.
    The part is called a banjo bolt if you want to search for it seperately or check in description.

    Cheers mully79. The banjo bolt on my M7000 is on outboard side, twice the length of the M7100 as it's also used to clamps the two caliper halves together so it won't work if the new one doesn't have one. Will search for ones to buy just in case it doesn't come supplied. 👍

    Thanks again for the heads up on the pushing pistons out method I'll double check it's seated properly and sort out using compressed air on bleed side if needed. 😎

  • reaperactualreaperactual Posts: 895
    edited October 2020

    If you can get the pistons to move, you are in with a chance!
    I have Shimano BR M520 (4 pot). One of the pistons cracked and jammed in, even the LBS couldn't get it out. That was a new rear calliper under warranty. The front calliper has had both pistons on one side jamming. The LBS struggled to shift them but did manage to free them off in the end. I have had intermittent problems with both brakes. I have to keep doing mini bleeds or adjusting the position of the calliper body. When they work, they work really well. But I am used to having Shimano brakes (SLX or XT)working well and faultlessly for years and years. Have Shimano gone too cheap?

    Hi Steve. Always been a die hard Shimano brake fan however this SLX rear brake has done my head in recently. It's stuck but not slanted or cracked as far as I can tell so hoping to get it moving a little at least before attempting to get pistons out.

    Not too bothered as buying a new one and first sign of difficulty stripping this caliper it's going in the bin and good riddance! Maybe quality control has gone down or corners are being cut with the issues you have had too? 🤔

    Hoping the new M7100 caliper will work as well as all other Shimano brakes have for me in the past, fingers crossed?

    Maybe I'll shop around, pay a bit more and look around for an XT instead? Thanks for the input, always appreciated Mate! 😎👍
  • reaperactualreaperactual Posts: 895
    edited October 2020
    Since receiving confirmations that a new M7100 caliper doesn't come supplied with a the necessary banjo bolt and it's going to cost an extra £7ish to buy the tiny little screw (unless I order one from China?) decided against it on principal.

    Thanks Shimano for the usual underhand rip off tactics!🖕

    Will now definitely be stripping my SLX down and hopefully sorting out the problem. If no results from that I'll look into a like for like swap or XT M8000 instead. Thanks for the help and advise. 😎👍





  • iso2000iso2000 Posts: 25
    On the subject of removing the pistons from the housing. This guy uses water on a caliper that has been removed from the bike to force the pistons out:

    https://www.youtube.com/watch?v=oRIMyk30eWw
  • reaperactualreaperactual Posts: 895
    edited October 2020
    Excellent iso2000! 👍 Recognised the Guys voice straight away and seen lots of Sick Bikers YouTube stuff. Definitely not spotted this video though.

    I've been searching around on internet for alternative methods and read a similar thing on an old forum post but using Shimano fluid rather than water.

    Appreciate the help and link, I'm sure it will be the cleanest and easiest way to get the pistons out. Nice one, thank you Pal! 😎👏
  • reaperactualreaperactual Posts: 895
    edited October 2020
    UPDATE:
    I used the water method to eject the pistons from the caliper just like in the You Tube tutorial, worked a treat and was easy enough.
    Stripped the caliper which wasn't that unclean but still worth a having a look.

    The normally exposed edge of the pistons are still dull coloured but are as clean as they possibly can be. Piston seals removed and cleaned along with the inside bore of the caliper itself. All sparkling now, Re assembled and did a full caliper up bleed with all new fresh fluid.

    Well worth the effort and a simple enough procedure in the end. Happy to report that both pistons are moving freely, getting a decent lever feel and all seems good. Keeping an eye on it over the next few weeks and hoping the problem is solved.

    Thank you again as I may not have even attempted this job if it wasn't for the help and advice you all gave. 👏👏👏😎👍

  • veronese68veronese68 Posts: 24,069 Lives Here
    Thank you for the update, had nothing useful to add but have been following with interest. Now filed in the back of my mind ready to be forgotten should I ever need the information :)
  • steve_sordysteve_sordy Posts: 2,239

    ..........Now filed in the back of my mind ready to be forgotten should I ever need the information :)

    That is where all my best stuff is! :)
  • UPDATE WITH PICS:

    Decided to strip the front caliper on my SLX too. Got a new mobile so took some pics for fun this time round.

    M7000 caliper


    Bleed syringe full of water


    Restricted the bleed side piston's extension and non bleed side piston popped out, good job my safety glasses were on.


    Split caliper.


    Blocked off transfer port with my finger and popped inboard piston out.



    Used a toothpick to get piston seals out and a good clean.

    Transfer port seal, piston seals and pistons back in place.


    4mm Allen bit for banjo bolt and T30 Torx bit for other bolt, job done.


    Enjoyable, simple and rewarding job and seems to stop pistons sticking.😎👍


















  • mully79mully79 Posts: 308
    Excellent job B)
    Even though they never look that bad there's obviously enough gunk to cause a piston to stick.

    I find fork strip downs and rebuilds are simillarly enjoyable and rewarding. I'm still on the original 2014 seals despite what the service manual says about changing them.
  • swjohnseyswjohnsey Posts: 263
    You can also get pistons out with a piston squirt type oil can. The seals and o-rings seem to last forever.
  • reaperactualreaperactual Posts: 895
    edited October 2020
    Cheers mully79 and thanks for the extra tip swjohnsey. Yeah, seals like new and supple.👍👍

    Not done a fork service before either but looking forward to having a go.

    The one thing I forgot to mention is not doing jobs like this on a brand new tablecloth. Wife had a right hissy fit when she came home! 😬🙈🤣
  • steve_sordysteve_sordy Posts: 2,239

    ......The one thing I forgot to mention is not doing jobs like this on a brand new tablecloth. Wife had a right hissy fit when she came home! 😬🙈🤣

    Oh you naughty boy! >:)
  • Lol Mate! 🤣😂🤣 Won't do that again in a hurry, nothing quite like a little physical violence from the other half to 'assist' in learning my lesson.👊🤕😩
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