Rear brake issue

[Mieju1]

Hi,
There seems to be many discussions regarding rear brake problems...however I didn't find any dealing with the issue I currently have. I get this funny jerking from the rear brake and even the leaver is pumping up and down under heavier braking. When I first apply the break it's all good, but a few seconds later it starts jerking....I've changed new quality pads and the disc seems straight and evenly worn. Also the caliber seems to be "floating" ok. I haven't yet changed the fluids. Any similar experiences/tips how to fix it?

[Rockbyter]

Could it be the ABS?

[Mieju1]

Could it be the ABS?

Mine doesn't have abs, it's the 2010 model....next I'll bleed the system to see if it helps.

[Magic Wand]

Are you sure the brake disc isn´t "warped"?

Spin the wheel and just Slightly apply light force to the brake lever, and maybe you will notice the pads touching the disc.

But on the other hand, sometimes the pads seems to touch the brake disc when I pushing my bike around at the parking lot, or similar, but i don´t feel anything strange when driving. No hot disc, no pulsing in the brake lever either.

Clean the caliper and every part you can reach, thoroughly, with Brake cleaner or similar.

/M

[Thirdway]

Might be a knackered master cylinder piston seal allowing pressure the release as the fluid warms up.