Sram code r stuck piston

[DaveNewing]

Hi. I'm trying to service my 2019 code r brakes as per the sram website video and one of the pistons won't come out. When I pump the brake lever with brake pads removed, only 3 of the 4 pistons move. One of the 3 good pistons then pops out and leaks fluid before the fourth piston moves. Is there an easy way to get the fourth piston out once you've lost pressure in the system?

 

[Gary]

Is there an easy way to get the fourth piston out once you've lost pressure in the system?

Yes. an airline.

 

[DaveNewing]

Yes. an airline.

Cheers Gary, I'll give a go tomorrow when I'm at work. Do you know if you can buy individual o rings for the codes, rather than a complete service kit? The smallest o ring on the banjo bolt is damaged.

 

[Gary]

I'd highly doubt it from SRAM/Zyro
if you have a supplier that stocks seals/O-rings locally it might be worth trying there.

 

[DaveNewing]

I'd highly doubt it from SRAM/Zyro
if you have a supplier that stocks seals/O-rings locally it might be worth trying there.

Thanks Gary. I do have a local o ring supplier, but the damaged o ring will be hard to measure accurately. I was hoping somebody might know where to buy the correct size from, or know what sizes are needed.

 

[DaveNewing]

Thanks Gary. I do have a local o ring supplier, but the damaged o ring will be hard to measure accurately. I was hoping somebody might know where to buy the correct size from, or know what sizes are needed.

The sram parts manual only state the seals as a complete kit, but as my codes are only a few months old, I didn't think that every seal and piston would need replacing.

 

[Zimmerframe]

Yes. an airline.

Can you get away with Ryan Air, or should you go B.A. ?

 

[Zimmerframe]

Same brakes, different question ..

Changed my rear pads a few weeks ago and the inboard pistons were hard to get back in.

Noticed yesterday that they were out and hadn't gone back in and one was out further than the other and had worn the pad off at an angle ..

Waddyado ?

 

[Gary]

Waddyado ?

fuck all. they're not my brakes

 

[Gary]

only a few months old

Warranty them. Or did you damage the seal fitting the banjo?

 

[DaveNewing]

The brakes were given to be by a friend who upgraded to hope e4. The o ring was damaged as I removed the banjo bolt from the caliper. I think the thread in the caliper caught the o ring and shaved a slither of the o ring off one side.

 

[Zimmerframe]

fuck all. they're not my brakes

OK .. so welcome live to "The Muppet Channel" ..

Had a few minutes so thought I'd clean my pistons as per youtube for when sramn pistons aren't returning.

Quick re-cap. Changed pads a few weeks ago and the inboard pistons (rear brake) were a pig to get back in .. then suddenly they just popped back in ..

Cleaning the bike the other day I noticed the outboard pistons were completely withdrawn, the front inboard was out part way and the rear inboard was out all the way (or a long way) and the pad was worn down to nothing at an angle.

Soooo ...

Removed pads, removed caliper.

brake fluid lubed round pistons. Pushed pistons in - only inboards were out. Tried again, only inboards came out. lubed. Again, they were virtually impossible to push back in then would suddenly go in.

Tried one more time and carefully made sure I didn't pop a piston out ..

The inboard rear piston popped out.

feck. So popped it back in. Pushed pistons back in .. again difficult then suddenly easy.

Pumped brakes ... 200 times .. (I counted as when I changed pads I noticed they needed about 50 pumps before the pistons came out).

Nothing.

Loosened top bleed screw - oil came out - tightened.

Any tips. If I loosen the bottom bleed screw, will that let air out ? Presumably there's air behind the piston if the piston fell out and I forgot to immerse the whole bike in brake fluid whilst working ..

One thing I did notice I the front inboard piston moves almost imperceptibly when you pump (you can feel it just if you hold it) and you can see it bubble a microscopic bit of fluid in and out. This isn't the piston which fell out.

 

[ImSundee]

TLDR

I'd say after you popped a piston out its time for a full bleed. Personally if you have any stuck piston, its worth a caliper rebuild and bleed, its a 3 0minute job to do so, unsticking doing the method you mention is a quick fix to be done when out riding or in a bind but never a proper fix, if its getting stuck it needs cleaning and rebuilding.