I guess this is a regular question, but I have a slightly different angle on it. Bought a new bike and the rear disk brake rubs - very loud and annoying. I took it back to the shop and they trued the disc - now it doesn't rub at all unless I'm riding the bike. When I'm riding, it's very loud. It's a great bike apart from the intolerable noise.

I guess the frame is flexing. It's a steel frame (Marin Eldridge grade), so more flexible than aluminum, and large, which may increase the flex. The brake is a Hayes So1e - single piston so maybe less gap than double piston? Is the brake compatible with the frame?

Anyway, I'm not sure whether to persevere with the bike or take it back for a refund. If I mess with it too much, they may not take it back. The senior mechanic who trued the disc seemed to know what he was doing - if he couldn't make it work, can I expect to? This is my first disk brake after 30 years of rim brakes.

Thanks.