I am trying to identify where the trouble is on my bike. At low speeds, my bike handles well, no issues. As I pick up speed though, it feels like the bike wants to veer slightly from side to side (that is the best way I can explain it). I have been running at lower speeds in traffic because, at this point, I don't know what is wrong. I have noticed the rear brakes will stop the wheel in rotation without the brakes being applied, so they do need some attention, anyway. But, I don't know if the brakes are causing this problem...I am thinking it is either the rear brake, or the rear wheel rim. Any advice on things I can check to pinpoint the problem? I am hoping it is not something more serious, but if it is the rear wheel rim replacing that could get expensive. Advice on what else might cause this type of thing.