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  1. If hydraulic brakes, then probably air in system. A bleed should fix it unless you have a leak. If cable, then maybe it snapped or came undone.

  2. Bike was fine on Wednesday. Today I completely lost braking to the rear. The shifter is going full travel with no resistance load. Shimano Shifter Ultegra ST-R8170-12-L, Hope RX4+ caliper. Pads intact. No sign of oil at the brake, shifter, or out the BB port. Obviously I can re-bleed, but I’ve no idea about the route cause. Brakes have been fine for 3.5 months, 2500km, since newly installed.

  3. Got air in the system. Had this happen to me when the bike was turned over for an on the road repair.

    Cheap and easy, fully depress lever and zip tie it to the handlebars, hang bike from the front wheel over night.

    If that doesn’t work, bleed the brakes.

  4. Heavy_Force_3571 on

    Take the wheel off and gently squeeze the lever and see if the brake pads move and exposs them to a point where you can reinstall the wheel. This may do it, often if the bike is stored vertically or moved fluid can get cut off in the system and this may reprime it. Otherwise take it your LBS.

  5. Check for leaks: under the hood and at the caliper. If no leaks, check that pads aren’t worn out. If no leaks or worn pads, rebleed the system.

  6. I recently added Hope RX4+ to my Shimano levers. I’m assuming that you got the correct calipers for mineral oil. Here’s what I found. There’s a known issue with the seal on the Shimano lever reservoir. I have replacements on backorder. If you bleed the brakes and they still won’t hold, I’d check that. My LBS has 3 bikes waiting for the part.

  7. If the bike is routed internally, I would pull the hose and make sure there isn’t a cut somewhere

  8. Shake_n_bake-9891 on

    You may have broken your brakes when you were bleeding the system…… Which SRAM do you have Apex, Rival, Force or the new Red?

  9. Hydraulics are fairly simple.
    1) sprung a leak, fairly easy to tell as hydraulic fluid dripping
    2) air in system, bleed the brake
    3) if lost pressure in middle of ride, either leak or your master cylinder in the brake failed. Needs a rebuild or more than likely unit replaced.

    I would diagnose in order 1, 2, 3

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