I use DOT fluid after pushing them out a tiny bit, Q-tip and wipe around the piston then push them back in. Be real careful not to push them to much or the piston can fall out. Before swiping them with the DOT I clean the entire caliper with alcohol.

If that does not help, possible it could be a warranty issue if they are still within the specified time.

 

It's really not unusual for one piston to move more than others even on just a two piston caliper if you don't have any load on the system. Think about the amount of pressure you apply even under light braking vs. what you apply to "push out the pistons" when there's no pads in the caliper. Push all the pistons back in, put the pads in, put a spacer in between the pads, pump the brakes out to apply pressure to the spacer. Without pushing the pistons back in, take everything back out and look at the pistons. They should be mostly even at that point.

 

this.

that one happy piston simply (hopefully) just has a little less friction than the others, and the fluid finds the path of least resistance.

At least that's hopefully what is happening, since I'm gonna be taking delivery of a new bike with the same brakes. (still havent decided if I wanna move my xt m8000's over...)

 

Yeap, Ive had this happen with Shimano brakes after hanging in the garage for a couple months untouched. Q-tip a fluid specced for the brakes fixes it for the rest of the season.

Sent from my SM-G950U using Tapatalk

 

So I held all 3 of 4 pistons back and made each one individually come out 5x, first time i cleaned with alcohol and put a bit of DOT fluid. they did come out much smoother after cleaning it.. after doing all of that i re bleed my brakes again as well just for precaution. ( i know some say dont use dot, but the sram service youtube actually did so i felt ok doing it)

i also replaced my rotors and pads, after they bed in they def got a bit stronger and now there is no noise. i think they are good but will be even better after a good downhill on the trail. i couldn't get the front one totally silent initially i heard the slightest rub but when free spinning it wasnt enough to slow it down, after the initial bed in it did dissipate a good amount to where i can't really hear it, i imagine some of the material wore off and evened out.

BUT.. i have 1 side of 2 pistons in front and back pistons out and the other two arent out much at all on the other side. both sides do move a bit when i hit brakes and look but they arent evenly out. is that normal???

should i still take it to the shop, they mentioned based on my description before putting on new pads+rotors that it may be a warranty issue but i tried to get them fixed and working as i dont want to lose my bike for a week or two while i wait for them to look and call and coordinate with sram.

Now... if they are warrantable... am i ruining new pads and rotors by riding on them?

 

The main problem with all Guide brakes is that before a certain manufacturing date the "master cylinder" pistons in the levers would stick (not return) in warm/hot weather and the slave pistons ("wheel cylinders" ) would not retract to the point of the brakes locking up solid in some cases.

This is a known warranty issue, there should have been a recall IMHO. See this thread.

Your retraction issue could be at the wheels or might be at the levers. If your lever pistons don't retract fully neither will the pistons at the calipers.

 

Just had this same problem, causing more lever travel as the pistons were not compensating for brake wear.
As the pads wear, the piston is supposed to slide past the seal to take up the travel. If the seal sticks to the piston, it can have an elastic effect causing the piston to return to the original position, causing excess lever travel. It's possible to block two pistons, hold a third with a pliers, and push the fourth one out to break it loose/ clean and lube with DOT4.
I accidentally popped out one piston and re-inserted it, then bled the system, then freed the stuck piston. I'll see what the longevity of this fix is, but it's making XT much more appealing.

 

I've had similar issues, GuzziBen. It's annoying but I found once I got my pistons unstuck, things worked well after that.

 

i had reset and pushed in numerous times but i have 1 typically stays in, any ideas? a shop said could be a warranty issue. any experience?

No big deal. In any hydraulic system of this type, the seals will exhibit slightly different friction, elongation, resiliency. The result is that every piston will move at a slightly different rate. The one that is coming out the most, is the one with the least friction. If you manually hold it in, one of the other three will move out further than the others.

The nonsense spewed from the mouths of bike shop "mechanics" never ceases to amaze me. It's a good thing you're doing the work yourself, so you can do it right.

 

For what its worth - the suggestions posted here have made a big difference. I took out wheel and pads, pulled on lever and noticed that one piston was making its way out before the others would, resulting in extreme brake lever throw (all the way to the handlebar). I have the level travel adjuster pretty close since this is for my son's smaller hands. Upon isolating the pistons using a few spanning wrenches and pulling on lever, i was able to clean and apply the DOT fluid to each piston. Hoping that this method lasts for awhile and doesn't become a overly frequent step to keeping this brakes operating. Thanks for the suggestions everyone!

 

I bought some SRAM guides rsc sets on eBay 2 1/2 years ago (warranty is 2 years). Over the last 6-9 months I’ve noticed the levers not returning especially in warm weather. I spoke to SRAM yesterday who said to take them to the lbs and they will fix/replace them at no cost as it is a known issue. I called the lbs and they have booked me in next week. Stoked to have the problem sorted.

 

I bought some SRAM guides rsc sets on eBay 2 1/2 years ago (warranty is 2 years). Over the last 6-9 months I've noticed the levers not returning especially in warm weather. I spoke to SRAM yesterday who said to take them to the lbs and they will fix/replace them at no cost as it is a known issue. I called the lbs and they have booked me in next week. Stoked to have the problem sorted.

That is the earlier version of the levers, this has been updated since 2017.

 

Take 4 pistons out, clean and replace the seal ring.
Piston moves in different rate...This is normal.Unless they get stuck.