Can anyone tell me how to fit a bicycle chain, 21 gear shimano?
Yep, easy one to answer, but would be easier if I could post a pic. Assuming the chain is open (meaning one link disconnected so that the chain has two ends) wrap the chain around the large chainwheel in the front and around the largest sprocket in the back (if you were riding the bike, this is known as cross-chaining and is frowned upon due to the wear/friction/resistance on the chain and components, however, the chain length needs to accomodate this possibility). Make the chain come together to loop these two gears (large in front, large in back) and note where the end of the open chain matches up with a ‘mating link’ along the chain. ADD two links from that point and use a chain-breaking tool to cut the chain there. Once you’ve got the chain to length, you can install it by routing it through the derailleurs and connecting the ends. Voila, perfect length for all gears. This link shows how the ends should come together:
