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Shimano Hydraulic Disc Brake Help - Odd issue?

joeyhalloranjoeyhalloran Posts: 542
Ok, so installed my new 105 R7020 shifters and brakes today but am getting a result I cant quite understand. on the rear there is a long lever throw, almost hitting the bar before the brakes apply, yet simultaneously the brakes are rubbing with no pressure to the brake lever. The front is set up perfectly, with light travel and a hard stop about 1.5cm away from the bar.

I did a full bleed and back bled the caliper, and have then tried the '5 min bleed' a few times using just the funnel and pumping the brakes, with to no effect. So, question 1, each time I do the 5 min bleed I get quite a few air bubbles, does this mean there is an air leak in the system somewhere, or just that when you open up the system you inherently get some air inside at it's this air that is then coming out?

Question 2, how can I fix this issue? The pads are a bit worn already as it's a second-hand set, if that matters.

Posts

  • photonic69photonic69 Posts: 1,002
    If you are getting bubbles then you still have air in the system. Unless you are seeing fluid leak under pressure I wouldn't think the air was getting back in. The system is under positive pressure usually so you'd need a negative pressure (vacuum) to suck air back in so I believe this is unlikely.

    I'd re-bleed again but this time push the caliper pistons right back into the caliper. Angle the bike in the bike stand so the hose is as vertical as possible from caliper to lever. Whilst bleeding tap the caliper and along the hose gently with the handle of a screwdriver to help dislodge any trapped air.
  • buhtosse40buhtosse40 Posts: 3
    Hi....if u still have the issue, try this worked for me, i had really spongy Ultegra disc brake https://www.bikeradar.com/features/give-any-hydraulic-brake-the-bleed-of-its-life/

    :):)
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