When replacing a chain you will need a chain tool. You can count the number of links in your old chain an install and exact duplicate. If, however, you for some reason are not sure of how many links you should have, follow this procedure. Put the new chain on the largest sprockets front and rear and bring the ends together. (Make sure that it takes the proper path thru the front and rear derailleur and pulleys). This should just about pull your rear derailleur cage until it is parallel with the chainstay (or the ground). Give it some assistance by pulling the chain taught if needed, then lift the chain at the top of the chainring (the front sprocket). You should then have between one half and one full link of extra chain at this point. Mark this length, as this is the length that you install. Another rule of thumb for chain length is this: when you are on the large chainring in front and the small cog in the rear, the rear derailleur should be straight up and down, or 90 degrees to the ground. An imaginary straight line thru both pulley wheels will be perpendicular to the ground.It will be easier to then go to smaller sprockets to join the chain at this length as it will not pull as much or be as tight on the smaller sprockets. Remember not to push the connecting link pin all of the way out while using the chain tool! Also keep in mind that if your chain needs replacement due to age, then you may also need to replace your sprockets too. Some chains, such as Shimano 9 speed, also require that you use a new pin every time you take the chain apart. If your chain is too long, it may come off easier in low gears, or rattle and hit the chainstay. If it is too short, it may damage your freewheel or chainring, or break, while going into high gear... Keep in mind that a chain will stretch with use, and when you install a new chain, it may not fit the teeth on the sprockets very well. If it doesn't seem to interdigitate smoothly on the chainrings or freewheel, you may need to replace those as well.. |
