Shimano R8070 Hydraulic Brake Shedding Stress


Hello, I’m on the finish of my information so hoping for some assist.

Personal a 2021 Tarmac SL7 with Shimano R8070 hydro brakes. They had been nice for a 12 months or so. On a random experience my entrance brake went utterly delicate. No obvious oil leaks or something. I bled it and was nice for a hand stuffed with rides then went delicate once more. Now i’ve re-bled it a hand stuffed with occasions and solely get about 20 miles of using earlier than it goes useless (lever begin shedding strain and finally goes all the best way to the bar)

  • i don’t cling or flip my bike the wrong way up.
  • i’ve adopted Shimanos ~20+ step bleeding course of w/ correct gear (funnel, shimano oil…)
  • no apparent leaks
  • i’ve changed the bleed screw to be sure that seal is sweet. cleaned all the things to make sure no particles. dangerous spot for sweat construct up
  • changed the pads to make sure worn pads weren’t inflicting something
  • hose connection on the caliper and grasp cylinder are tight, no apparent leaks

When bleeding the primary operation is to push fluid from the caliper up into the funnel. Shut the bleed nipple on the caliper and function the lever 10 occasions. Once I function the lever I see air bubbles arising on every stroke of the lever. I’ve made positive the funnel is safe and is making a very good seal. bleed nipple is tight. From right here i’ve executed a gravity bleed and the fluid coming from the caliper has no air in it… When shut the bleed nipple and return to lever operation i nonetheless get small air bubbles coming on the finish of each stroke.

I’m misplaced.

So as to add to the strangeness, my rear brake did the identical factor a few week in the past and misplaced strain. It’s a gradual regression of strain however inside just a few miles it was gone. I adopted the Shimano bleed process and all the things was by the e book. First experience was profitable and it stored strain in contrast to the entrance on the identical experience.