Question About Rear Caliper...

Discussion in 'Technical Help' started by Johnnymoto, Nov 12, 2020.

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  1. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Hi to all. My T100 has a rear sticking caliper, happened after it got hot ( smoked ) on a long downhill two up, and It got me by surprise, lost rear brake fully. Since then, it sticks a bit, I hear it rumbling when I start riding every morning, I ride it every day to work. I noticed, on both my Ts, the rear caliper pistons get a bit “corroded-dirty” on the exposed piston area. Last week I had ti scrape the pistons on the Thruxton caliper before I mounted new pads. I ordered a used caliper from EB, and is in great shape, but the pistons look a bit corroded also, so the question is..... Can I safely remove the pistons for a clean and polish work before I install it ? I know, if I push the pistons in, for the new pads, they will stick as they are dirty. Is kind of difficult to polish the pistons while mounted, can I take them out and put them back wothout a special procedure or tools ? Has anyone done it ? Before I mess it up...
     
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  2. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    You can certainly remove the pistons and clean them up. Use a fine metal polish NOT wire wool or a wire brush on both pistons and bore. Light use of a nylon pan scrub is just about ok. You would be well advised to replace the seals while you are at it and the banjo washers (or anneal the old ones). The brake hose may also be showing its age,

    Those underslung calipers attract dirt and benefit from a periodic deep clean and polish of the brake pins. Re-assemble with brake grease and bleed vertically before you reassemble on the carrier.
     
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  3. Bad Billy

    Bad Billy Baddest Member

    Jun 1, 2017
    6,800
    1,000
    Southern Softyville
    If you remove the pistons you will need a seal kit, they are sometime svery tricky to get back on after cleaning without the right press or tool.

    What I do for the race bike is use a 'G' clamp to hold the piston one side in place, then gently pump the brake lever forcing the piston in the other side out a bit, be careful not to go too far, then gently clean the piston with wire wool & brake cleaner, I normally use a tiny bit of silicone grease on the piston before releasing the clamp, then push the clean piston back in & repeat the process on the other side. When you have done both then clean excess grease off with brake cleaner then refit the pads.


    g.jpg
     
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  4. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Thank you very very much !!! I watched a video on YT and it seems fairly simple, but is the brakes, my bikes brakes and I many times take my woman up / down the Mountains and I ride hard, brakes are more important than the engine itself !!! I will pull the pistons out and see how they look inside. Thats why I got a spare caliper in case one goes / is crap. I ride this bikes every day, they are my daily dose of PTSD control !!!!
     
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  5. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Thanks a whole lot !!!! I have maintained my everything all my life, but have never dare to take caliper pistons out, I always had bought new calipers instead. But a new caliper is around $700+ for me, and I have two Ts both with the same issue on all calipers. Thanks a lot to all you are helping my wallet to stay healthy !!!!
     
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  6. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Here is a photo of the used Caliper I got from EB, it shows the same identical “dirt/rust” in the pistons. When installing new pads, the pistons will have to be pushed in to allow the space for the new Thick pads, so, this dirt/rust will get trapped between the pistons and the caliper cylinders and get stuck or have lots of drag, causing the pistons not to return back in, causing dragging pads, hot caliper, loss of braking when really needed. So, I will pull the pistons out, clean them carefully and properly, and then, TRY TO REINSERT THEM BACK INTO THE CALIPER, I will post how hard or easy it is, and how well the caliper works after this new challenge for me. ( I know is wise to install new rings and seals, but I will do that after I try this with old rings ). image1 2.jpeg
     
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  7. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Very kind from you on explaining what you did and the recommendations. I have not worked on mine yet, I will probably do it next week. Thanks again !!!
     
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  8. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    The caliper is mechanically very simple. Lump of metal, two big holes, pistons and 4 seals (2 main plus 2 outer dust). A small hole at the back admits brake fluid.....

    The key parts to polish are the bores and the pistons. Brass polish works very well. It is very finely abrasive and will polish away corrosion. Replace the seals and lubricate with brake fluid to re-install pistons.

    We’ll get to bleeding later!
     
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  9. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire
    I did have a wonderful video of the following but seem to have deleted it.

    Can you see what is going on in this photo - for stuck piston removal?

    If you can "get in to" the piston, then this hasn't failed to work (well...only once and that was on a piston that was totally corroded in).

    Put a standard socket in the piston, and also the square end of a socket driver. It needs to be a close fit. As you then rotate the driver the 'cam effect' should all lock the socket into place, and as it does so you should then be able to rotate the actual piston. If you can rotate the piston gently pull up (or pull on the piston) as you continue to rotate...pulling the piston out.

    You may need to play with socket/driver sizes to get a good fit.

    As others will testify, I ain't not no expert...but I managed full caliper strip down. clean and rebuilds on my 955 Triple...sincerely, if I can, anyone can!

    Caliper.PNG
     
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  10. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
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    Abingdon, Oxfordshire
    here is it in action! From 3m50s

     
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  11. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Thanks a lot !!!!!! I was going to do it but the difficulty of removing the pistons made me put it on hold. I was thinking on how to get the pistons out without having to connect the caliper to the hyd line and pump it out. I will try that, looks easy !!!!
     
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  12. Callumity

    Callumity Elite Member

    Feb 25, 2017
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    Nr Biggar
    My immediate go to are water pump pliers followed by a grease gun for control you can’t achieve with an air line. If nothing is disconnected use the hydraulics and block each piston in turn til they’re both nearly pushed out.
     
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  13. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire
    You're welcome....it is a pleasure to share. When I first did it I couldn't stop smiling...there was such untold joy in something so simple!
     
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  14. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire
    Just as an addition...and I did feel like my calipers refurb turned in to "Triggers Broom"; but whilst I was this far in and upgrading bleed nipples, banjo bolts, pad pins etc all to SS....it seemed a shame to spend a lot of time trying to tidy up slightly pitted and now 18yr old pistons. They really didn't cost much to buy new.... And I didn't get ss pistons either. I felt 'the normal ones' lasted 18yrs....so some new normal ones will do the job perfectly.

    Again, as you're this far in, be sure to have a better clean than you think of the veins that feed the piston reservoirs. The tiny veins that actually run inside the caliper ...Mine where full of a waxy jelly type muck that didn't 'wash' out but needed to be mechanically cleared. I found 'interdental brushes' perfect for this....
     
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  15. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    When my T100 caliper went bad ( sticks a bit ) I said “ I will just buy a new caliper and done “ but I find out it will cost me about $700 bucks. So I guess is time to learn something new. Thanks a lot.
     
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  16. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Will do thanks !!!
     
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  17. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire
    Yeah, agreed. I was quite shocked as I'd actually replaced the fluid literally a few days before - before deciding to get my hands proper dirty and getting everything stripped.

    Having changed the fluid a year before.

    I did wonder then how many times the fluid had been changed, and not shifted that muck.

    I do remember the brakes being better/not spongy at all after the deep clean.

    Your chemistry is clearly better than mine. But "waxy jelly stuff" was the most technical I could get :p
     
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  18. joe mc donald

    Dec 26, 2014
    13,874
    1,000
    slough / burnham
    I have found in the past it is not the calliper but the two sliders on there they dry out and start seizing so do check them. With the calliper and mounting plate the calliper should should slide freely or the wheel out.
    Joe.
     
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  19. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
    45
    68
    Puerto Rico
    Thanks will check that too !
     
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