If the chain will not stay in the correct gear, visit your nearest Blix dealer or local bike shop for a derailleur adjustment (hub gear adjustment for Vika Travel). If your gears slip when you pedal hard, your chain and possibly gears may be worn out. It is best to check for chain wear regularly with a chain-checker and replace it whenever indicated. Most riders should replace their chains every few years. Frequency of use, weather, terrain, pedaling style and maintenance will affect how often parts must be replaced.