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
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    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
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    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
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    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
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    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
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    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
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    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. Big Sandy

    Big Sandy WOOF! WOOF!
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    I have just done similar on my 97 Sprint, rear caliper stuck, total loss of back brake (not that I use it much).

    I looked for a second hand spare... There were a few in the US, but none in the UK, there was a guy offering rebuild and recondition at about £80 on ebay...

    I bought a set of stainless pistons and seals, kit included stainless bleed nipple and brake grease.

    After removing the caliper, there was no way the pistons were coming out easy... I used piston pliers to pull them... They weren't too corroded, but I replaced them anyway. The reason they were corroded and stuck was because the previous owner hadn't fitted the outer seals, and the pot was full of brake dust and crap.

    It was actually an easy job to do. I have done plenty of car wheel cylinders, but this was the first caliper I had done. It was a very pleasant surprise!

    Sticking on has put the rear disc slightly out of true, so looking for a replacement for that. My mot tester says it's not bad enough to be bothering with, but, brakes man, brakes!
     
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  8. Big Sandy

    Big Sandy WOOF! WOOF!
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  9. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
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    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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  10. Callumity

    Callumity Elite Member

    Feb 25, 2017
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    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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  11. Big Sandy

    Big Sandy WOOF! WOOF!
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    I think one very important part is to make sure that all parts that should move can move.... Mine has a part that moves in and out (think its a slide its called) on two pins. Ideally I should have replaced the rubber thingies (haha, I said 'rubber thingies' I mean boots, I guess ) but couldn't get any, so just a damned good clean, and plenty of red rubber grease in the boots. Coppaslip on the back of the new pads, and a bit on the antisqueal plate.

    It was a bit fiddly getting the pistons in, but I have carrots for fingers, and I managed it!
     
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  12. DanielB

    DanielB Well-Known Member

    Jan 13, 2019
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    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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  13. DanielB

    DanielB Well-Known Member

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

     
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  14. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
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    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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  15. Big Sandy

    Big Sandy WOOF! WOOF!
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  16. Callumity

    Callumity Elite Member

    Feb 25, 2017
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    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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  17. DanielB

    DanielB Well-Known Member

    Jan 13, 2019
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    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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  18. DanielB

    DanielB Well-Known Member

    Jan 13, 2019
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    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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  19. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
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    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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  20. Johnnymoto

    Johnnymoto Well-Known Member

    Nov 11, 2020
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    Will do thanks !!!
     
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