Replaced tube in back tire and upon putting back tire back on somehow messed up the gearing. I need to know how to readjust the gearing so I can switch gears again when riding. Attempted to do it without the manual and adjusted the cable to tight to shift through all the gears. Shifting period is difficult. So I guess I need to know how to adjust the gearing so that I don't over tighten the cable but still have the proper tension.