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I have SRAM Guide R hydraulic brakes.

The problem is, the rear brake piston won't come out from the lever body. so I decided to bleed it but it's still less responsive even though I already lubricated the piston assembly with DOT fluid.

Here's what I did:

  1. Removed the wheel and brake pads from the calliper, then inserted the bleed block.
  2. Prepared my syringes with DOT 5.1 fluid. 1 is 1/4 full and the other one is 3/4.
  3. Removed the bleeding cup of the calliper and inserted the 3/4 full syringe and close the clip.
  4. Set the lever full extended and used a rubber band to hold and squeeze the lever to the handle bar.
  5. Removed the bleed screw on the lever and inserted the 1/4 full syringe.
  6. Started the bleeding procedure by opening the clip of the syringe attached on the calliper and push the syringe.
  7. I can see the old fluid coming in the syringe on the lever. I pushed until 1/4 and closed the clip of the syringe attached on the calliper.
  8. Removed the syringe attached on the calliper and inserted back the bleed cup/screw.
  9. Removed the rubber band from the lever and pulled the handle of the syringes attached on the lever to removed the air from the system and closed the clip.
  10. Removed the syringes from the lever body and reinserted the bleed screw.
  11. Cleaned the lever body and calliper with glass cleaner.
  12. Reinserted the pads and wheel.
  13. Fully squeezed the lever and touched to the handle and squeezed again but the lever didn't touch to the handle bar again.

Now, the problem is the piston is not responsive but its better than before I bled system.

Do you think its better to upgrade with saint or zee?

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  • Brakes is the one system on the bike that simply must work when you need it. There's nothing wrong with getting the LBS to work on your brakes (other than cost)
    – Criggie ♦
    Commented May 30, 2016 at 4:59

1 Answer 1

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Sounds like a sticky piston to me. These can be a real pain to sort.

To get the unstuck you remove the wheel, and push the pistons in and out a handful of times.

  1. Stick the bike in a sturdy stand.
  2. Remove the wheel.
  3. Squeeze the levers a few times to get the pistons sticking out a bit. Don't go too far as dropping a piston out is bad news.
  4. Push them back in. Repeat as necessary.

Another way I tried was removing the pads, and sticking an 8mm allen key in the calliper, clamping it between the pistons and holding the level down with a strap.

Then you can gently move the pistons back and forth together.

You shouldn't need to lube the pistons, just make sure they're clean. The in and out will lube the bits that need to be lubed.

SRAM say 3-5, my Maguras took a lot more than that.

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  • And one more thing Alex, when I pushed the piston inside lever body it never comes out again. That's the biggest pain in my ass this time. So, I tried to drain the fluid, reattached the cable from the lever and push the piston backward through the whole using hard wire. The spring itself cannot even push back the piston.
    – John Caballero
    Commented May 30, 2016 at 4:45
  • You shouldn't need to disassemble the brakes to do this. If pulling the lever doesn't push out the pistons try holding the other side in with something so all the pressure is acting on only the sticky side.
    – alex
    Commented May 30, 2016 at 4:48
  • Also, make sure you push them in straight, if you get them wedged in on an angle, they can be a pain to straighten, and don't got in any further than flush with the caliper body.
    – alex
    Commented May 30, 2016 at 4:50
  • I tried all those things but the system has no pressure so I must disassemble the brakes
    – John Caballero
    Commented May 30, 2016 at 4:52
  • If there's no pressure, try bleeding again. Keep trying until there is pressure. Bleeding can be tricky and take a few goes to get it right, especially the first time.
    – alex
    Commented May 30, 2016 at 4:53

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