Sticky pistons. Whats your method?

My Sram Guides are in need of a bit of love and attention. Some of the pistons have become a bit sticky.

I usually pump the pistons out a bit and give them a bit of washdown with brake fluid and push them back in.

What methods do others use? Any really good techniques for getting them good and clean?

When I had repeating issues with sticky pistons, I fitted BB7s. No problems any more 🙂

On my road bike maybe. On my MTB no chance.

Dunno why, I’ve used BB7s on roadys and MTBs for years. They’re brilliant.

Same as OP. I might work them in and out a few times to help lift the dirt out.

If I’m feeling indulgent I’ll use some hunters silicone lube on them, but it’s a slower process because it’s more viscous.

See Park Tool videos in PB, they recommend flossing the piston to remove the build up causing the sticking. String and isopropyl alcohol from memory.

Pump them out. Clean with ipa on q-tip. Lube with finish line stanction lube. Reset pistons. Job done

Dunno why, I’ve used BB7s on roadys and MTBs for years. They’re brilliant.

For a mechanical system they are ‘brilliant’, because most mechanical discs are terrible.  Compare them to any decent hydraulic system and they aren’t so great.  Which is why they don’t get spec’ed on MTBs.

+1 for the park tool method – push out floss with string push back job done

I am always wary of tutorials that advocate “lubing” the pistons. Friction between the seal and the piston is what makes a caliper work correctly, if you lube that interface the pistons won’t retract anymore. The only two moments when the pistons should slide against the seals are when compensating for pad wear and when being reset (pushed back) during bleeding/pad change.

Pretty hard to find good information on “piston rollback” ( https://textar-professional.com/textar-training-center/brake-piston/ )

This pre-stressed sealing ring, which encompasses the brake caliper piston also serves to retract the piston when pressure decreases (“rollback”) and to re-adjust automatically the excessive clearance due to pad wear. Because of the rollback effect of the sealing ring, the piston will be retracted when pressure decreases.

In order to prevent the clearance from increasing during unbraked driving due to disc distortion, excessive disc runout or heavy vibration, a slight piston shift in the direction of the caliper housing is possible. The piston is always retracted to its initial position because of the “knockback” effect (see Fig.2).

I clean mine gently with fine sand paper and some WD40, just to remove the dirt (when the pistons are in situ)

Also I popped out a piston by accident the other day when cleaning them and gave that a proper clean

See

Hunters silicone lube, apply with bristle paint brush, Q tips are naughty single use plastic.  I usually push the pistons in and out a few times before putting the pads back in to make sure the lube has solved the problem.

For some reason I’m finding this way more of an issue with Guide brakes than previous SRAM/Avid brakes (inc X0 Trail which had the same calliper as the earlier Guide models).

I’ve tried the floss/string method and pumping each out while holding other pistons in. Wasn’t great but seemed to improve, but go on a ride and they’re sticking again mid ride. Barely any bite distance and being RSC I’ve tried adjusting bite point. In fact that works briefly and then it sticks again, so adjust the bite all the other way and that will free them also, then stick again.

I’m thinking only solution is to get a piston & seal kit, but that means having to pull apart and a full refill/bleed. My attempts at bleeding brakes doesn’t always go well.

Oh, and I think I’m right that if I pump enough for a piston to pop out, then fluid leaks out and it’s bleed time (and probably new seals)?

Not sure if your issues is grime or just needs some TLC but there’s a well documented issue with Guides having issues when in the heat / direct sunlight, it’s in the lever apparently not allowing the oil to return and sticking the pistons…….  I sent some brand new Guide RS’s back this week and the shop said, “Not another set!, don’t worry we’re returning them all, have your money back”… Lots of activity on this issue on here and other forums.

I think it may be time for new seals and pistons to be honest. The rear brake does have discolouration in the fluid so maybe this combined with the sticky pistons may mean it’s a good time for a lot of TLC.

I did see the brake flossing video and it looked pretty good! I’ll try that and see how it goes and possibly order new bits too.

So with regards to removing pistons, do you pump them all out quite far, then split the caliper, then remove them?

I had not seen that issue greavo, I will do a bit of research!

have a thingy made up of a couple of flat bits of metal and some wing nuts – remove caliper/pads bolt it tight on the good side to keep that piston in position then carefully pump out the stuck ‘un  then qtips and olive oil for me

never had 2 stuck pistons and don’t go to 4 so no idea if all stuck

Hunters silicone lube, apply with bristle paint brush, Q tips are naughty single use plastic

ok until a badger comes round asking what you’ve done to his mates

Similar issues back in the day with Avid Juicys, I ended up cycling pistons in and out, cleaning everything up, even rebuilt one with new seals, and at one point split the caliper so I could use a G clamp to force the pistons back in. FWIW, I used the bikes through winter, ususally with some gritted roads during the rides, so probably a bit more corrosion than would be typical occurred on mine.

Then I spent £40 or so on a full set of some cheapo Shimano brakes that were far less prone to this issue and needed bleeding less often too (although the bleeding thing probably depends more on factors other than just the brakes, I’ll just say that I am mediocre at bleeding the Shimanos 5 years down the line, and I got very very good at bleeding the avids).

Obviously Guides are a bit pricier, as would their Shimano equivalent be, and I’d hope the pistons on Avids don’t stick as much as they used to, and I know Shimano have had some reliability problems (luckily none have affected me), but I’d still rate them as much lower faff.

I use the same method as I use on my motorbike calipers to clean the pistons to make sure they all move at the same time.

Remove brake pads, push piston out a small amount (may need to hold in the other piston(s) if one is being stubborn). Toothbrush with some soapy water (washing up liquid), give the pistons and surrounding area a good scrub, remove all the brake dust. Spray caliper with brake cleaner, this gets rid of all the soapy water and will evaporate. Push pistons back in and give them another scrub with the toothbrush to get the bits you missed. Spray with brake cleaner again. Pads back in (give them a spray with brake cleaner too) and you’re good.

On motorbikes (which generate a load more brake dust) this is a regular maintenance thing to do to ensure the brakes perform as they should, I see no reason why you wouldn’t do this every few months on a MTB brake disc set up. I did exactly this on my dad’s commuter bike with tektro disc brakes at the weekend, in the front caliper one of the pistons was stuck and was barely moving, after cleaning both pistons were pushing out simultaneously.

Also keep on top of the cleaning and they won’t get stuck, it’s the brake dust/crap on the piston that ends up corroding it, once you’ve got corroded pistons you’re in caliper rebuild territory.

Not sure if your issues is grime or just needs some TLC but there’s a well documented issue with Guides having issues when in the heat / direct sunlight, it’s in the lever apparently not allowing the oil to return and sticking the pistons…….  I sent some brand new Guide RS’s back this week and the shop said, “Not another set!, don’t worry we’re returning them all, have your money back”… Lots of activity on this issue on here and other forums.

Was thinking along these lines as well. Although I’m not sure if its hot enough yet for this happen?

I have just been through this process with my Guide RS’s. If you didn’t now about the lever plunger issue you would prob assume its the caliper sticking, but in actual fact its the plunger sticking inside the lever body. You can either take the plunger out and sand the ends down (just don’t try and take the seals off – I tried and ripped one of them so had to buy a rebuild kit) or by a new kit. You can use the Gen 2 plunger for the older guides, which I have done. The plunger has been redesigned and the plastic looks/feels different. My front brake feels 100% better now and my rear brake that was the “good” feeling brake, now feels like crap compared to the front. I have just received a new plunger from Taiwan (rather than buying a whole new kit) to do the back. Its a pretty simple process – explained very well in Sram Guide Manual.

silicone lube,

*childish snigger*  searched on Amazon, not sure whether to go for Durex Play or Pjur Backdoor..

When I asked a similar question on here about sticky SRAM road pistons, somebody recommended Red Rubber Grease which I had never heard of before. It worked and now if pistons start to stick , I remove pads, push pistons out a little , clean pistons and apply the red rubber grease. Then push pistons in and out a few times and reassemble- job done .