chain skips on rear cassette
I have a Specialized Epic mountain bike that is about 4 years old. I ride in a weekly race series and we race rain or shine. After 3 weeks in a row in the rain and heavy mud I found it very difficult to shift gears so I took it into the shop and had them replace the cables and housing for my gears. I could then shift again but the chain would continuously skip out of the sprocket at the rear for no reason and jump to another ring. It was even worse when I pushed hard like up a hill. I took it back and they got it so it was smooth on the stand. Within 1 min of me riding, same problem. The shop now has replaced the cables, the rear derailler, the chain, the rear cassette and the shifters and it is still doing it (although not as bad). The bike shop guys test rode it and they said it was fine. Two different guys rode it (both are serious racers) but they weigh about 130 and 150 pounds and I am 190 and as soon as I ride hard it still happens. I trust them as I know them personally and have done a lot of business with them over the years so I do not believe that they are trying to screw me. I am really frustrated. Does anyone have any ideas why this would continue to happen even when everything is now new. Thanks.