Tech Talks: Fixing Sticky Pistons, Presented by Park Tool – Video

Sep 28, 2017
by Pinkbike Staff  
Tech Talks Presented by Park Tool


Tech Talks Presented by Park Tool is a monthly video series hosted by Park Tool's own wrench whisperer, Calvin Jones. The series covers the A to Zs of some of the most prevalent repair jobs, with the fifteenth episode showing you how to cure sticky brake pistons.

The disc brake has been one of the most important products of the last few decades, but they're far from perfect. Like most things, they require some love every once in awhile, and if you don't give them some attention, they can work poorly or even start slowing you down when you don't want them to. When brake pistons don't retract back into the caliper, it's often because of a corrupted surface on the piston that rides back and forth on the seal. And if it gets really nasty, one or both of the pistons may decide to stop moving altogether. Park Tool's Calvin Jones is here to show you how to use a strip of cotton and some solvent to fix those troublesome pistons.


Fixing Sticky Caliper Pistons

Views: 24,382    Faves: 66    Comments: 6



Need more Calvin in your life?

Episode #1 - Tubeless tire installation and conversion
Episode #2 - Saving that bent disc rotor
Episode #3 - Derailleur hanger alignment
Episode #4 - Shimano and Crankbrothers pedal service
Episode #5 - Trailside wheel repair
Episode #6 - Trailside chain repair
Episode #7 - Derailleur limits and cable tension
Episode #8 - Derailleur setup
Episode #9 - Fork wiper seal replacement
Episode #10 - Clipless pedal setup
Episode #11 - New cleat setup
Episode #12 - Top 5 next level shifting issues
Episode #13 - Fixing cassette play
Episode #14 - Gearing hacks

Stay tuned for more mechanical how-to videos with Calvin returning on the last Thursday of every month to show you the easiest way to get the job done. Want to know more? Park Tool's how-to section has you and your bike covered.

www.parktool.com / @ParkToolCompany


107 Comments

  • + 51
 Sram owners need to watch this video!! Hahah
  • + 2
 True! I have Elixirs that's got sticky pistons as well. Never had this problem on any of my Shimanos.
  • + 6
 Hahaha this comes at a perfect time, the Guides that came on my bike has sticky pistons both front and rear xD
  • + 0
 Yesss, perfect timing. Just wanted to assemble my old Guides Ultimate on my DJ mash up - neither rear nor front brake make a move. Wanted to ride the weekend, now I will need to sit in the workshop :/
  • - 11
flag henryz4 (Sep 28, 2017 at 4:25) (Below Threshold)
 in my experience, 99% of sticky pistons cases have been caused by wrong resistance spring.
I explain: on my avid trail I installed aftermarkets pads with the included spring. After 2 months I had a sticky piston problem.
I completely disassembled the caliper and overhauled it. After 2 months, happened again on the same caliper.
Comparing the spring to the OEM I noticed that the OEM was stronger and stiffer compared to the aftermarket.
So I just replaced the pad spring with the OEM (without cleaning or lubing the pistons) and never had a single sticky piston again.
IMHO spring has a very important role in the health of your caliper piston(s). Check it before loosing your s**t trying to solve the problem.
  • + 26
 @henryz4: The little metal spring is purely designed to prevent the pads rattling, not to aid piston retraction. Piston retraction is down to free moving pistons and pressure differential from front to back faces (atmospheric versus oil) as well as seal deformation. When pressure is removed it's the seal that acts as a return spring.
Pistons are designed to creep out of the seal to take up pad wear and give consistent lever throw.
Imagine the impact of a strong spring causing full return on worn pads - loads of free stroke on every lever pull.
  • + 1
 before I was on Shimano I was running Elixer 3's and were great for a while. Started having issues left and right and yeah bleeding Elixers was a pain. I graduated to Elixer 5's thinking they were gunna be better but ended up having the same issues on top of having sticky pistons. I thought my brake pads were worn but after taking it to get looked at they had to mess with the pistons. Glad I'm running Shimano XTR's
  • + 20
 I finally figured out how to fix the sticky Guides.. Step 1, buy some XTs.
  • + 8
 @SkipSkovhugger: there are a lot of guides/levels that have issues in the lever, which make it seem like the pistons are sticky. Lever won't fully spring back and pistons stay extended.

This is a warranty issue, if this is what is happening to you. Fyi.
  • + 8
 @owlie: xt's have issues too. Shifting bite point being the one that drives most people crazy.
  • + 1
 @FLATLlNE: It's a sticky piston in my case.
I have MY17 Guide RS's, so the levers have the new res. piston assembly that doesn't expand in warm weather.

Furthermore, I even know which pistons in the caliper don't move. I noticed it the last time I bled them :-)

Thanks anyway though, I'm sure some people still don't know that the lever thing is a warranty issue, as SRAM have been really quiet about it, as it's due to heat, so not everyone's affected.
  • + 2
 Yup - and always cheaper to just get a new set usually when it gets to this point anyways - You're probably dealing with a 5+ year old brake when it gets that gunk built up. You could do all this work and still have an internal issue somewhere along the line.
  • + 1
 @owlie: why not SLX?
  • + 12
 "Fluid and Tears" is may favorite track by the Sticky Pistons
  • + 0
 @owlie: you do realize that this happens to all brakes not just avids you dick riding sheep!!!
  • + 2
 I'm an SRAM owner and I approve this message.
  • + 5
 Atleast guides you can replace pistons. Zees you can't...gotta buy a whole new caliper.
  • + 2
 @SkipSkovhugger: if your guides aren't this year models the pistons sticking alright but it's the master cylinder pistons and you need a rebuild kit. when it gets hot out the nylon piston expands in the bore and the levers don't come back..Sram don't tell you that. but if this is your issue go to a bike shop and they should be able to get you a kit free from sram. they should recall them, that's a safty issue. I already fixed mine..
  • + 1
 @tomonda: if your guides aren't this year models the pistons sticking alright but it's the master cylinder pistons and you need a rebuild kit. when it gets hot out the nylon piston expands in the bore and the levers don't come back..Sram don't tell you that. but if this is your issue go to a bike shop and they should be able to get you a kit free from sram. they should recall them, that's a safty issue. I already fixed mine
  • + 1
 @mountguitars: Maybe you should stop running 1000 year old brakes and get with the programme then bro.
  • + 2
 @mbiker35: Look at my previous reply to flatline.
They are the new model, I'm aware of the lever piston assembly issue that plagued the older models, I don't live in any kind of hot climate so we're not really affected by it.
And lastly, I have seen which pistons do not extend when pressing the lever.
3 pistons move, 1 stays put. And it's like that at both ends.
  • + 2
 @mbiker35: it's the worst. We have warrantied one of my girlfriends brakes. But they won't do the other until it becomes a problem. So basically we have to risk her safety! Pretty cool.
  • + 1
 @mountguitars:
Yeah they just leak and you can’t repair any part of them.
  • + 2
 @LiquidSpin: This is one of the funniest comparisons to me. I am in no way denying the fact that the Elixer brakes especially the lower end models are pretty shit for the most part. But everyone alway replaces them with Shimano XTR or XT the 2 highest end Shimano brakes on the market and compares a low end brake to one that is very high end,
  • + 1
 @newusername:

Actually, I didn't technically replace them with Shimano XT's or XTR's.

I kept using the Exiler 5's until I retired the bike. The new bike came with Shimano XT components. Then from there I decided to upgrade to XTR just to deck the bike out in full XTR bling.

From what I've read and from hearing about SLX they are just as good just a little heavier and made with cheaper parts. My buddy rides SLX and has never complained about them.

My personal experience was not good when it came to Elixer's. I tried the 3 that came stock on my bike and then the 5's and same issues. Frown
  • + 31
 This is sponsored content done right. Calvin, you're the man!
  • + 29
 This is the best piston cleaning video I've seen so far. The spacer trick is superb! Personally, the inboard piston has stuck more for me. Cheers Calvin!
  • + 18
 The SRAM guide problem is in the lever, not the caliper. Trust me I know.
  • + 0
 this is true. different piston
  • + 2
 True that bro - 2016 models and below have internal issues that are listed on their warranty site.
  • + 2
 Can agree there. Rode the Sram Guide R's for little over a year and both levers gave up within 1 month of each other...
  • + 3
 @Jack-McLovin: Swollen master cylinder seals.

Still, good video, useful to know.
  • + 1
 At least you can buy spare parts for Sram. If your Shimano starts leaking from lever, it's most probably done for.
  • + 10
 even tho I'm a decent home mechanic I was totally unaware of this. I have some stuff to do this evening now! THX
  • + 10
 I always also apply the silicone lube hope recommends for their brakes. Works like a charm
  • + 1
 yes clean the then light coat of plumbers silicon makes pistons retract easier .
  • + 8
 Girlfriend:
"What are you doing?"

Me:
"Flossing my brakes."

Now Ex-Girlfriend:
"Jim, I think it's time we move on, my friends say it's weird that you floss your bike."
  • + 4
 Most women have the ultimate bike, and maintenance solution, which is never ride it. It's built right in for them.
  • + 10
 Calvin you rule!
  • + 5
 If 95% of riders maintained there calipers as often as they wipe there a??, They wouldn't have an issue. Stop blaming manufacturer's for your own lack of maintenance. In the video the mechanic forgot to lube the Piston before pushing it back into the caliper. Brake fluid changes yearly he!p a ton.
  • + 12
 Wow not all of us are so poor that we can't afford servants to wipe our asses bro
  • + 9
 So you expect me to maintain my calipers more than once a day? Unlikely. Especially if I have irritable bowel syndrome. I'd be maintaining my calipers like a maniac
  • + 0
 @1armbandit, how is changing the brake fluid helping sticky pistons? Brake fluid has nothing to do with sticky pistons. Brake fluid changing procedure itself has nothing to do with sticky pistons as well.
  • + 2
 @mentalhead: If you've reset pistons that were dirty, you may have pushed that dirt past the piston seals. It's now in the fluid, and if you clean the pistons as in this video, you may still have gunk on the other side of the seals wreaking havoc. It won't be a major improvment, but flushing the brake fluid may help with sticky pistons in this case.
  • + 1
 Tip: use a grinder to turn your yellow shimano bleed blockers into a one sided block that allows you to safely hyper extend one piston at a time without over extending it. You can even modify one for quad pot brakes so you only extend one at a time. Those bleed blockers are a dime a dozen at shops. Make sure to hyper extend each piston 6-8 times after cleaning/ lubricating.
  • + 7
 Good luck with a 4-Piston Brake... getting around all pistons won't be too easy. otherwise super cool video!
  • + 7
 Just did this the other day with a mechanic at Kami games on my older codes with a four piston caliper. Used a 10mm box end wrench to hold 2 pistons back at a time and protrude the others. Cleaned them with a q-tip and alcohol, rubbed a little brake fluid on them and they work great now.
  • + 5
 @mxben13:

Bingo! We have a winner!
  • + 2
 hahaha, I have Hope 6 Pots on one of my bikes. but honestly I've never had this problem and I've run them since 2008.
  • + 2
 Servicing a rental fleet, it seems to be the inboard pistons sticking more often. What's the cause of inboard sticking more vs. outboard? Lower temperatures of outboard piston having more airflow? More dirt contamination on inboard piston?
  • + 1
 Yeah, the inboard sticks more for me too!
  • + 1
 So I tried this on one of my sticky pistons, came out super clean, but now I can't push the piston back. The piston won't go back enough to get the pads in. I think some dirt got behind the seal possibly, it feels crunchy when I try pushing the piston back. Any suggestion?
  • + 2
 You should check to see if the piston is in one piece. Lots of pistons are ceramic and can break when you press them back, often described as a crunchy feeling when pressing them back in.
  • + 1
 I have done this but then added a non-petroleum based grease to the pistons before inserting the pad. Use a Q-Tip an smear a small layer then cycled the pistons in and out a few times. Thought about it after; the dirt might stick to the grease but it's been no problem so far.
  • + 1
 Once my pads are in, and before squeezing any levers I use different sized shims like the ones used for checking gaps, when adjusting valve lash on a motor. I put them in between the disc and pad, both sides, squeeze lever, pistons center themselves. Seems to work pretty good once everything is clean, until it starts to get contaminated again with dirt, brake dust, mud and they start to stick again. Nature of the beast. The other option is don't clean shit and have your crap drag all day long slowing your ass down! LMAO
  • + 1
 Inboard. SRAM Guide owners: the caliper rebuild piston job is a PITA; however, dirty pistons are also the issue for returning the pads correctly (all piston hydraulic caliper brands will suffer this). Calvin is the MAN! This string tip is solid. I've always used Q-tips and alcohol with limited success. Lots of 'tarter' build up on mine and the dragging brake issues gone! And I also see my inboard pistons sticking more. Thanks PB for these vids!
  • + 1
 In reality my brake systems work pretty well for years. If they become a problem I'll just pick up the latest and greatest because I make good money and I can. Look for my used brakes on EBAY...hahahahaha
  • + 5
 I love these videos!!
  • + 1
 I feel like my mind is melting, or I'm just becoming more realistic. As a teen, "Oh f*ck yeah bud, I'll be the bicycle man, I'll manufacture the manufactures". Now, "they do a pretty great job, and I know nothing".
  • + 1
 With Avids, I've found the 'plaque' can't be removed and the only repair is piston replacement. The piston wall gets rough and won't slide smoothly no matter what.
  • + 2
 Overlooking that fact that he demonstrates on Avids...
  • + 3
 Inboard piston, rear. Thanks for the great video Calvin !
  • + 1
 Really good way of doing this, Cheers guys!

Also can the Mods not just put a poll under the video for the Left vs Right piston?
  • + 1
 Damn. That's way better than my method of just squirting some mineral oil on the pistons (and contaminating the pads in the process).
  • + 1
 Cheers Calvin, brilliant as always. Inboard piston from memory (memorys not great mind)
  • + 0
 I like to do this and then follow the cleaning up with que tip and some dot grease, helps to lubricate the piston and seal after.
  • + 2
 Just happened to watch a Sram video on overhauling Guide calipers and it specifically warned against using DOT grease to lube piston seals as it may prevent the pistons retracting into the caliber bores and impede braking performance.

www.youtube.com/watch?v=Ihb2cBiXp2U
  • + 1
 @cornichons: Very interesting, thanks for the response. Ive been doing it for years now on my guides haha :/ ...oops
  • + 1
 For Canadian change that's 3 toonies (a tad more than 5mm) or 3 loonies (a bit less than 6mm).
  • + 1
 Great vid and good cleaning tip... I have always use cotton buds but string is a good idea!
  • + 1
 Front, outboard piston. XT. Great video, I'm now armed to be a sticky piston hygienist! Thanks!
  • + 3
 What a cool fork haha!
  • + 1
 Calvin is da Man! Great vide much better than using q-tips! BUT do not use acetone, it can eat your seals!!!
  • + 1
 Come on just take the pistons out clean them and replace all the fluid.
  • + 1
 It's always the inboard that sticks on my Avid BB5s.
  • + 2
 Hahaha. I see what you did there.
  • + 1
 Car brake cleaner works great, and is harmful to the enviroment Eek
  • + 1
 Is "Bike Hacks" from youtube on pink bike?
  • + 1
 The last two times it was my inside piston that got stuck on AVID brakes.
  • + 1
 my inboard right piston get stuck more.
  • + 1
 I think my inboard piston gets stuck more often.
  • + 1
 I ride with shimano brakes...problem solved!
  • + 1
 Bud, same problems. And some other ones too.
  • + 1
 I really enjoyed this.... one of your best.
  • + 1
 Inboard. Great video Calvin
  • + 1
 Cotton earbuds work well for cleaning pistons too.
  • + 1
 Hey a tip!!!
  • + 0
 Definitely inboard piston in my experience.
  • + 1
 great tip!
  • + 1
 Inboard
  • + 1
 inboard
  • - 2
 I really enjoy Calvin videos but the truth is that if you want to clean pistons really well you should remove them from the caliper.
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