When im braking and progressively brake harder eventualy my rear brakes kick in and they squeek.

Rear discs and pads were changed in june so theyve gOt good life left in them. I stripped them down today, i cleaned everything withcleaner ten copper greased everything and still squeeky.

This a common problem?

What causes this?

Cheers

Just for reference, copper grease isn't the absolute best lubricant for this purpose. There's a product called ceratec which is better.

If this set-up uses them, do the slide pins move freely?

Clean the edge of the disc off, if they get a lip they can squeek. It will also help if you sand a small edge of the pad away, only on each side though not top and bottom.

i had set years ago, and no matter what i did nothing stopped the squealing, just had to change them in the end