Help! My chain pops off
Hey all, I have an '04 Jamis exile with stock components. Whenever I'm peddling with a lot of torch in low gear (up hills), my chain pops off. Most of the time it comes off the front derailer completely. Other times it skips to a higher gear in the rear cassette. My bike's been tuned up, no one can find anything wrong with it. What's wrong? Thanks.