I have a Trek Mountain Bike 820 that I am going to retire this winter and get a new Trek Madone Road Bike. My 820 is close to 15 years old and this summer has started to clunk only while pedaling. Not on every revolution all the time but does seem to be in the same spot all the time. Another problem is you can't hear the clunk but you can feel it in your feet. Even more evident now that I have clip less pedals. But I am not sure I want to totally retire this old bike. It has been great and I may want to use it on the trails in the winter plus my wife loves this one over her 820 because of the fit.

Is some of the cranks on this bike the same as many other bikes. I have a couple old bikes that ride nice just that they are beat up, wheels bent and derailers probable worth less also. I was thinking if generic I could steal the crank and back gears maybe buy a new chain to keep this bike running and maybe this winter I would have time to do the work myself. Hate to part with it as the frame has barely a scratch on it.