I would be very grateful if someone could advise me on a big problem with my new bike.
Recently bought a Scott Aspect 620 with Shimano M395 brakes.
I tried the bike in the shop and immediately noticed that the rear brake squealed heavily when used. Sounds almost like a car horn.
Being a noob, I asked about it and was told that this was "normal" and should go away when brakes are broken in. I believed them.
After about 200 km, the problem persisted and got worse, until at some point, there the lever had gone very spongy and the rear brake was virtually inoperable. There was also oil residue around the brake area.
I took it back to the shop, where quite a disinterested looking mechanic looked at it and just bled the brakes. He then told me that the brakes were contaminated and he heated the pads to clean them, but didn't know what the problem was.
While the brakes still sort of work, they squal as they did before. Again, there is buildup of oily residue around the brake, some 80 km later.
The front brake worked fine and silent since day one.
What should I do?