Fixing a stuck bicycle disc brake piston [1019]

[@BikeGremlinUS]

If you have any questions, please use the BikeGremlin forum - I try to respond to every comment, but KZbin sucks at notifications, especially when it comes to any follow-up questions. www.bikegremlin.net/ A couple of articles that might help How to eliminate disc brake rubbing: bike.bikegremlin.com/7975/disc-brake-rub/ How to solve disc brake squeal: bike.bikegremlin.com/8037/disc-brake-squeal/

[@truthmatters1950]

Solid, comprehensive, practical, well paced, easy to follow presentation in language everyone can understand. I'd never done any maintenance of an hydraulic brake before my son presented me with his bike with both pistons stuck against the disc - and this clip got us sorted! Thanks Bike Gremlin for sharing your skills and knowledge.

[@christerpkarlsson72]

Without this awesome video I would not have dared to fix the stuck piston myself! Love to you sharing this.

[@eldershawn]

Thank you I just did this today for a 4 piston system and installed new brakes! Thanks a million! Everything worked perfectly. I just used a little paint brush to apply the mineral oil to the pistons.

[@Jetsonn]

Dude, THIS is what I’ve been looking for! Exactly what I’ve been looking for the whole day. 10-15 videos and none of them were what I needed. Thank you.

[@BikeGremlinUS]

Cool - glad it could help. :)

[@keithk888]

THANK YOU! I just could not get rid of my front brake rub even after upgrading the rotor and pads, followed your instructions here and then the steps on your website for alignment and steps 4 & 2 finally got it sorted out.

[@alexnice9847]

That's my issue: one brake piston doesn't move anymore and the other one barely. It happened after a few weeks of inactivity. It is very surprising as it seems to be the only video about that issue. I thought a bleeding would solve the issue but it didn't and then I found your video.Thank you.

[@BikeGremlinUS]

It works for both bicycle, and motorcycle disc brake pistons. Haven't tried it with any cars, but I don't see why it wouldn't help there too.

[@joeminton105]

Both of my pistons are stuck. I thought it was low fluid or worn pads. Turns out piston are stuck. New caliper BR RS785 Shimano is almost 70$ US. think i will try this out! Hope it works

[@veste75]

thank you immensly, you are the only one addressing this sticking piston issue out there; i' ll try to fix mine tomorrow, hope it goes well.

[@Dreamer11_]

Thanks!! I was fixing brake noise, and I didn't know those pistons need to be checked. Indeed after cleaning it became better.

[@BikeGremlinUS]

Cool. Glad to hear it helped. :) Relja

[@AKhan-bs3cd]

Thank you so much! This solved my issue. I have to say you’re the only one who has a video on stuck pistons!

[@eyesuckle]

Well done! A clear, methodical and well-shot video. I particularly appreciate your recommendation of cheaper alternatives (like the automotive brake cleaner) to some of the more expensive products from a bike shop.

[@paulhewitt1488]

Terrific explanation and great camera work to show the time and patience required to fix a way too common problem. Thank you 👍👍

[@johnspeth794]

One of the most helpful bike repair videos I've seen. Thanks.

[@withlovemora]

Thank you so much for this video! I found it very easy to understand and clear to see everything you were talking about. Much appreciated ✌🏽🚲

[@SARW15]

Great video. Thanks for putting in the time to share this really useful step-by-step guide for disc brake issues. Lots of great details from beginning to end.

[@chrisnumnuts8671]

warning dont have your outer cable sleeve to long on disk brakes it can course them to lock on. I spent 2 years with the problem I went as for in getting a new bike after coming off the bike and knocking me knee cap out of place .recently cut the outer casing 4 inch shorter greased the inner cable it works :)

[@strategicthinker8899]

Brake cleaner into the piston grooves, then wd40. Let it sit for 30 minutes. Check, reapply wd40 if needed. When working, spray with bake cleaner again and put some oil in the grooves. Should work. If not, you'd need to disassemble and burp the system afterwards.

[@Samthemancharles]

Great video. Thanks for explaining and showing, I especially appreciate where you show that it wasn't quite functioning properly. That was nice to see you just had to do some more cleaning and such. I need to do this to two of my bikes because here in California bike labor is 70 to $90 an hour. Seriously!! I also noticed I can buy that tool for $20 that has that on one end and disc straightener on other end. Your English is exceptional except at one point, sorry no cc available. Subscribed!

[@BikeGremlinUS]

Cool - glad it could help. :) Unior makes the tool with a slit in the middle - so the same part is used for straightening discs and spreading calipers: uniortools.com/eng/product/1757-2DP-2-for-1-disc-brake-tool#881686 I bought two separate tools for that, for (arguably?) better ergonomics, though I would expect the 2-in-1 version to work fine. P.S. Bike shops in my city charge about $10 to $15 per hour, which means, when all the taxes and rents are paid, mechanics usually work for up to $600 per month (starting pay is about $350). Based on my calculation, at about $25 per hour, one could live quite well from bike mechanics in Serbia (not sure about the US costs of workplace and apartment rents, electricity, food etc.). However, no one here could afford such prices, so no shop can charge that much. So they break-even with repairs, and make profit from sales, mostly. I like to joke: The best way to get to 1 million dollars in the cycling business is to start it with 2 million dollars. :) Still, for me, the best thing about doing stuff on my own is not any money savings, but the zen, and the confidence it brings. I love being able to fix my and friends' bikes even in the middle of a mountain. Lets you go further with no worries. :) On my last ride, I was the only one with a chain tool - all the other people thought "why would a new chain break?!" But one did. :) So for me, fixing other people's bikes came as a by-product of wanting to fix everything by myself on my own bikes. But my IT job pays all the bills - not leaving that. :) bike.bikegremlin.com/7340/mechanic/

[@thankmelater1254]

Finally I was able to fix my brakes. Thank you!

[@peterstecks7660]

Excellent work. Thank you. I will be trying to free off my pistons tomorrow. This has been really helpful. Thanks.

[@xxmilixx4316]

Man i haven't tried it yet cus my pistons are stuck but i so hope this works and as it looks in the video, it looks pretty real ill let you know if it worrks by me

[@BassSwirls]

Just fixed a persistent sticking piston , funny enough I use LHM mineral oil. £5 litre! Anyway one piston was lazy I had to use a brush and oil. Took 15 mins of back and forth pumping lever and resetting it. Now my pads are perfectly centred and moving equally. Clean off with isopropyl alcohol after.

[@lethal0weapon7777]

Where do you get it from for that price?

[@BassSwirls]

@@lethal0weapon7777 I can't find the receipt...but a Google should bring you to a good deal.

[@nollybippy]

Thanks for the video amigo! Same problem I'm having. I'll try fix it tonight.

[@BikeGremlinUS]

Good luck. :)

[@zlatanfazlagic]

Thank you very much. Great video and super detailed instructions.

[@FlorinSirbu.]

Great video mate, finally my piston's freed and I am very happy. Cheers.

[@jafamils1]

i have problem with 1 pisotns it wont go back all the way, like it need 1-2mm to go all in what i shuld do

[@jupiter604]

Thank you for explaining!

[@roscored1000]

Very well explained

[@junboo8730]

This video is awesome. You can see all the trouble he went through. Best video out there.

[@mrcorona2093]

What I don't understand is this. After doing these operations, when I press the brake again, the part inside the caliper is still protruding out and not going in. What is the solution to this?

[@BikeGremlinUS]

Hi, I've made the BikeGremlin forum for any technical questions: www.bikegremlin.net/ It makes it a lot easier to post pictures (when needed), and keep track of questions and replies (KZbin notifications for channel "owners" are not very easy to keep up with). Relja

[@zezem]

For a stubborn stuck piston: I have thought about slippng a M16 washer in the disc groove between tool and free piston, to allow more lever pressure?

[@BikeGremlinUS]

I've got a tool to hold one side of the piston(s) in place, preventing them from going out. This is what I mean (Amazon affiliate link): amzn.to/2YztsFv I've used it on stubborn motorcycle calipers, using it not in between the pistons, but on a caliper outer edge and in between, pressing one piston in place (the side that moves more freely), with some cloth to prevent scratching. Then, pumping the lever to push the stuck piston(s) out. Not sure it would even fit bicycle calipers - never used it, never needed it. Hand pressure with the bike brake piston tool was always enough to hold pistons strongly enough for the more stubborn side to be pushed out. But, in a pinch, I'd improvise something like that, only smaller (must check if the motorbike tool fits first, I think it's too thick). Not sure about how exactly you mean to use an M16 washer. If you mean sticking it somehow to keep the tool pressed against the freely moving piston, in order to push the stubborn piston out, I think it's worth giving it a try - if hand pressure alone is not enough.

[@guille9434]

Nice video, thanks!

[@chadkline4268]

I hate disc brakes on bicycles. They freeze and stick in cold weather when moisture freezes and expands in the assembly. Also, the rear brake cable is often curved up so that water goes right down the cable and into the cable conduit, where it freezes. Seeing this video reminds me of why disc brakes suck in bicycles. What happened to center pull brakes? They work just fine! Without this kind of nonsense. I use Vaseline for everything. Works great.

[@BikeGremlinUS]

Yup. After having been fixing dozens, I did give disc brakes a go on my own bike(s), as an ultimate test. Went back to rim brakes and never looked back. I ride all year long, with weekend rides on mountainous terrain (though weekly commuting is done on flats I admit). Having said that, if my commute were in a mountainous region, I might consider some disc brakes, at least for the front (i.e. give them another chance).

[@chadkline4268]

@@BikeGremlinUS thanks! I thought I was alone in my thinking about disc brakes. I live near the Arctic circle, and they are too much trouble. But it is very difficult to find bikes with rim brakes. Thank you for your reply. I appreciate it.

[@wazzup105]

Thank you. That really helped.

[@OYeahan]

I am not sure about lubricating bike pistons, maybe they first work better, but then all the grime sticks much better to the part of the piston that extends during breaking and then goes back into the caliper, taking the grime with it. Isn't that a problem? I have seen the grime on the pistons myself.

[@BikeGremlinUS]

A great question. To answer it fully: Pistons are lubricated before being pushed all the way in. Then, it is all cleaned (degreased) - I hope that part is clear from the video. Afterwards, as the pistons get pushed out (further and further, as the pads wear), there's a very thin layer of braking fluid that wasn't cleaned by the seals, coating the piston sides. But this happens regardless of whether you lubricated them before pushing them all the way in, or not, since the part of the piston behind the seal is coated in brake fluid either way. To further discuss the grime sticking topic - it's worth considering: In very wet conditions, especially on salty winter roads, for cars and motorcycles it helps using a coating of grease (I know, sounds crazy, doesn't it? :) ) - red rubber grease (that one doesn't harm the seals for DOT brake fluid calipers). Rust being a greater problem than any dirt build up. Now, with car and motorcycle disc brakes, scratching is inevitable, but for bicycles, any sort of scratching or drag is unacceptable (even though that's an inherent flaw of disc brake systems, but that's a separate topic for a discussion). Still, even for bicycles, there's a dilemma: is more grit worse than rust? I suppose it depends on the riding conditions. For dry riding conditions, I guess that dry piston sides are a better option. For the wet - I'd argue it is vice-versa (though, I've only used the red rubber grease on motorcycles, never on bicycles, since I don't own any disc brake bicycles myself, and I suppose other people would find the suggestion to be crazy so I never offered that :) ). Further feedback: This particular bike (shown in the video) was ridden since that day, in all sorts of conditions, and didn't have any problems. A month ago I did a tune-up service on it, and the brakes were fine. I'll probably replace the brake fluid in autumn/winter, see if there's any excess dirt inside or similar (not expecting any, but we'll see), unless brake pads need replacing before that (can't recall if they were nearly done, or still OK, but the owner is a friend and lets me know if there are any problems, he's decently competent so I didn't bother writing it down). Either way, that's not a statistically valid amount of data - I don't service thousands of hydraulic brake bicycles per year, but so far I've had good results with the methods shown in this video. Both with bicycles, and with motorcycles. If (when? :) ) I run into any problems, I'll try to figure out the causes and update my procedures.

[@OYeahan]

Thanks for such a long and quick reply! I haven't considered that the pistons shouldn't (at least theoretically) actually slide back in against the seal during riding. So as far I understand, the cleaning is just not to introduce the grime into (and past) the seal when the pistons are moved back (and therefore they should both be cleaned first before any of them is pushed in), and the pistons are lubricated not to actually lubricate the pistons themselves, but to lubricate the seal surface so that the pistons slide easily against it when they need to (that is when they self-adjust after service and then later dur to the pad and disc wear). The part of the piston that never touches the seal when riding actually doesn't benefit from any oil, so maybe it would make sense to install the pads after such service, adjust the caliper and center the pistons, and then take the pads out for a second and clean the protruding part of the pistons with a brake cleaner/IPA (without moving them of course)? That way the part of the piston that contacts part of the caliper bore after the seal wouldn't collect mineral dust so easily, but IDK if that matters and if there is such contact at all.

[@BikeGremlinUS]

I think any extra cleaning after the brakes have been installed and the pistons pushed out to reach the disc (i.e. self-adjust) is a lot of hassle, with no clear benefits. I should make a video on how the hydraulic disc brakes work exactly and what goes on as the pistons self-adjust and move. Until I do that, a short answer is: pistons won't move back in past the seal when the brake is released, it's just the seal's rubber that pulls them back, without practically any movement of the pistons inwards, relative to the seal.

[@OYeahan]

@@BikeGremlinUS ParkTool has an excellent one with a caliper cross-cut and animation, hard to compete with that :D. It is interesting that there is enough friction between the piston and the seal so that the seal can pull the piston back with enough force. Also would be nice to understand how exactly this works in tandem with the lever so that the pad clearance can self-adjust - is there only one port in the lever cylinder? Is there some unidirectional valve there? Why in Shimano brakes I need to sometimes push the syringe piston quite hard before the oil pressure breaks some resistance (in the lever probably) and the oil starts to follow up to the funnel? Such a simple system, so mysterious :D

[@BikeGremlinUS]

I'm bad at drawing, and appalling when it comes to 3D animations, but those are some very good questions that deserve a separate video each. :)

[@goran1986m]

Kako da znam koje je ulje u pitanju, imam tektro auriga hidraulicne kocnice... Ocistio sam pistons-e ali nisam nista podmazivao ?

[@BikeGremlinUS]

Koliko znam, Tektro koristi mineralno ulje kao kočionu tečnost (tj. može Total LHM Plus). Naravno, najsigurnije je guglati po tačnom modelu.

[@goran1986m]

@@BikeGremlinUS hvala... jeste mineralno, sad sam pogledao. Znaci mogu sa mineralnim uljem da podmazem malo ociscene "pistones" da bi se bolje kretale pri kocenje ?

[@BikeGremlinUS]

Da.

[@goran1986m]

@@BikeGremlinUS Hvala !

[@alanezaron3236]

great video, thanks

[@NickForest999]

Really useful video and did the trick...thanks😎

[@behzadehdaie7866]

perfect like always👍🙏

Puno hvala!

[@alanbowen5140]

Thanks for a great video

[@higgybabes]

Thanks, great video. V useful.

[@und3rgr0undfr34k]

thank you!

[@0_1_2]

Thanks brate!

[@mtbboy1993]

But what to do if you have to get stuck pistons out to change the piston seals? Mine are are stuck. The seals leak, I get air in the system, can't get it pistons out, apart of one that sometimes pops out. Seems like I need an air compressor.

[@BikeGremlinUS]

Most calipers are held together with two bolts - screwed in from one side to the other. Unscrewing those bolts lets you split the caliper into two halves. When doing that, be careful not to drop any o-ring seals (and be mindful where they go back, even if replacing them). Once the caliper is "split in half" - you can more easily grab a piston with your fingers, and work it out (don't use any pliers to not scratch the sides, as then the seal will leak once you reassemble it). If it's stuck and rusty it might take a bit of patience, but it should work. The problem with using an air compressor is that you can't get both the pistons out. Once one piston pops out, the other side will have no more pressure build up. In theory (I haven't tried doing that), you might be able to use the channel that lets the fluid run between both sides as a "tool" - closing it to pop one piston out, and sticking an air gun to the other side's channel to pop the other piston out (not sure if I've explained this well, but once the caliper is split apart, it becomes quite obvious). Hope this helps. Relja

[@mtbboy1993]

@@BikeGremlinUS the problem is they won't lift out, I can't press any harder ont he syringe to move the pistons out.

[@mtbboy1993]

@@BikeGremlinUS defenitly not rusty one piston popped out but can't ge yth others out, put the piston in to refilled with fluid tried to let the other pistons come out, but it's stuck. They move but not enough.

[@mtbboy1993]

@@BikeGremlinUS the brakes are Formula Cura 4. It's 2 years and one month old. I've cleaned and lubed pistons to prevent issues. But now pistons randomly get stuck and unstuck.

[@BikeGremlinUS]

In that case, if they won't go out enough for you to get a good purchase (grab) with your hands, an air compressor may be the way to go. Though, to get both pistons out, you'll probably need to disassemble the caliper into the two halves and push each piston out separately Ideally, try to hold the piston away from the hose side in place, so you first push the piston closer to the hose side out first. Then, disassemble the caliper, insert the hose into the fluid channel of the piston that is still in, and push it out with air pressure. Alternatively, you could unscrew the hose, close the hole with a screw of appropriate thread pitch, then disassemble the caliper and push each side out using the air compressor inside the fluid channel.

[@timb9998]

FAB video

[@pabloguerrero7560]

If the piston doesn’t want to push back in does it mean i need to get it bleeded?

[@jakeb1778]

Probably slightly over filled master cylinder. Totally fine except when you go to to retract piston. Make sure piston is clean before trying to push in and if they refuse to go with reasonable force then you need to open the port on the brake lever and then push piston back. You will loose some fluid. You do not want to introduce air to the system. For my brakes (Shimano) I use the bleed cup and fill it with a little oil that way air cannotnnot enter the system. Also the proper way to do it is with a bleed block and that way you know you have the right amount of fluid

[@OYeahan]

@@jakeb1778 it is quite easy to blow the compensation membrane in modern Shimano levers when pushing pistons in with overfilled master cylinder, as it is apparently designed to be cut on the plastic part, probably for safety reasons (master cylinder over-pressure when system completely overheats and the pressure kicks back to the master cylinder?). If you're not sure if the MC isn't over filled, always open the reservoir first, and place either some cloth or a funnel to capture potential overfill not to make a mess (however that might introduce some air to the system, but you might proceed with some simple 'lever bleed' with the funnel afterwards).

[@SalahDSalim]

I feel like this gave me hope but i don't have that flat tool and that mineral oil but i have i care degreaser and alcohol Any alternative tools?

[@BikeGremlinUS]

I suppose that for moving the pistons out of the way, a similar tool can be improvised from steel, iron, or even hard wood. For cleaning I suppose warm water and dishwasher liquid can do the job - just rinse thoroughly.

[@SalahDSalim]

@@BikeGremlinUS thank you sir

[@vaidasn6781]

Nice video, thnx!

[@madmaxhyper]

I pull my brake too hard it locks up

[@andrejtrickovski2507]

Is it okay to bleed my brakes with total lhm oil?

[@BikeGremlinUS]

Bicycle brakes use either DOT brake fluid, or mineral oil. For those that use mineral oil, I've had very good results with Total LHM Plus.

[@andrejtrickovski2507]

Okay thank you i will try it, great video btw

[@mcgrozozo]

I da li moze lhm plus za punjnje kocnice tj za blidovanje?

[@BikeGremlinUS]

Yup. :) To koristim.

[@mcgrozozo]

Da li moze wd40 umesto tecnosti za ciscenje kocnica?

[@delooloobreee]

Nije preporučljivo, WD ima mali procenat lubrikanta koji može da pravi problem.

[@jandebuyssere]

I have one caliper that doesn't want to come out en one who doesn't want to retract.. Double trouble!! 🙄

[@chacklet4542]

Hey man, did u fix it? I have the same problem

[@jandebuyssere]

@@chacklet4542 no, bought a new set.. 😉

[@R3FL3X84]

i had to split my caliper in half. and take both the pistons out they was seized lol they are 5 years old avid elixir.

[@rgbungee1420]

Mind if I know what model shimano brakes you're working with?

[@BikeGremlinUS]

Sure - the frame at about 6:42 says the model is BR-M447 kzbin.info/www/bejne/gWfQeGmLn6ebZrM Principle was the same for any other model (and manufacturer) I've worked with.

[@31.8mm]

how if the piston stuck won't back in? i found this issues back when I work as mech, the customer seems to over use the brake until the pads died, i was thinking maybe the piston overheated and melted lil bit. but not sure what's exactly happened

[@31.8mm]

@@BikeGremlinUS thanks sir :)

[@talxfon]

I got the same problem. I changed the mineral oil, it was better but it's not near perfect. My mechanic says it has to be replaced...

[@datogadelia]

replace oil

[@31.8mm]

@@datogadelia as far as i can remember , it didn't work

[@jedunboxing4127]

do you just push the pistons ?

[@jedunboxing4127]

@@BikeGremlinUS now I get it after experimenting,i did removed the screw cap of the breaks on the handlebar and was able to push it gently it reset the position of the pistons,now at first I removed the brake pads,and I pressed the breaks,then the oil leaked,I just figured out why they put something in between the pistons when bleeding..lols

[@davzrobaichjukes]

🖐 5

[@ЛёхаБукреев]

Русский, судя по акценту? =)

[@BikeGremlinUS]

Близу. :) Српски. www.youtube.com/@BikeGremlinRS