Hi there guys! I've got 9 speed gears on my jump bike, and they're skipping. The cassette's worn down so it's all sharkfinned. Do you reckon that's the problem? I've tried quite a few times to set the gears today, no luck, except on the larger rings, which are less worn. It only started today when I put a new chain on. I know that using a 8spd chain on a 9spd cassette produces the same effect, but the two chains are definately 9spd, and the same width. Help me please! This bike is my method of getting to college!