What is “Chainline”?
On most mountainbikes you have three front chainrings and anywhere from six to nine sprockets on the rear cassette. With the drive chain linking the two, obviously there has to be some relationship between the positioning of these drive parts in relation to each other for acceptable wear and shifting performance. If we just sit and think of the setup we can visualize the three rings up front plus, let us say for simplicities sake, seven sprockets at the rear. Would you agree with me if I said the middle ring up front should line up with the middle sprocket at the back? You would? Good, then we are on the same wavelength. As a quick chainline check, shift to the middle ring and the middle sprocket. Lean the bike against a wall and squat down behind the bike. Look real carefully along the chain from the front chainring to the rear sprocket. The chain should run straight back without angling off to the left or the right. This is pretty subtle, so check carefully. If you have eight gears a
