The cables that run form your shifters to the gears have stretched with age. Its time to go the you local bike shop (LBS) and get them the adjust your shifters. If they are a good shop they will charge you $10 for their beer kitty, If they arn't they may hit you up for a $80 "tuneup". You might want to call a couple of LBS and ask the price.
Between Crystal River and Hernando, Florida, 6 miles west of the Withlacoochee Trail
I've had several since 1999 but have settled on my beloved 2001 Litespeed Tuscany and my latest, a 2013 Cannondale CAAD 10.
The cables will stretch while the bike is sitting in the garage. They are under tension in almost every gear.
Most cyclists either take their bikes back to the LBS to have the cables adjusted after 3 to 6 months or if they are knowledgeable about bike repairs will do their own adjustments.
Originally posted by pokey Buy the book 'zinn and the art of mtb maintenance' for $20 or go to www.parktool.com and check on their maintenance stuff.In no time you will be smarter than many here.Good luck.
Hey, I would take that personal, if it wasn't true.
Youall realize that we're creating another biking addict!
Also, don't forget you should avoid using the extremes in your gearing. Don't use the combination of the big chainring (front) and the largest rear cog (i.e. the one closest to the wheel--i.e. gear 13), and don't use the small ring and the smallest cog (i.e. gear 6). The idea is that you don't want to have the chain running at too much of an angle--it'll wear out the parts faster. Moreover, there is always some overlap in the gear ratios (so, gear 11 is likely close to the same as gear 13).
Some would say you should also avoid gears 7, 12 (mid front with smallest and largest in back).
Shift down to 6th gear....(small small) Loosen the bolt on the dreailleur that holds the cable, and pull the cable tight if its loose. If its pretty tight already ude the barrell adjustor on the back of the derailleur to make it shift right, turn counterclockwise for more tension. If the chain shifts over the top gear, tighten the bottom screw on the derailleur until the chain dosent go over the top and your set to go.