when iam riding the bike it makes a real loud grinding sonud and starts wobboling likes its fixint to fall ouver or have a flat tire when i take the brakes off it doesnt do it the brakes are pretty worn almost completly gone but i dont think that would cause that but iam no expert either i dont think the roter is bent cuz i was riding it and about 30 mins in to the ride it started can some one shead some light on what going on here