Make sure your derailleur sits at the correct height. The derailleur should fall around 1 to 3 millimetres (0.039 to 0.118 in) above the large chain ring.[1] X Research source When the derailleur cage sits too far above the chainring, this can cause the bike to shift poorly. If it is too far below, the derailleur will rub against the chain rings.[2] X Research source Fixing the height is a subtle adjustment, based on a difference of millimeters. You will need to be precise. Having your bike on a repair stand can make this work easier. You can use a penny to try and estimate if you have adjusted to the right height, as a penny is 1.5 millimetres (0.059 in) thick.[3] X Research source Adjust the height with the positioning clamp. This clamp is what connects the derailleur to the frame of your bike. Loosen the derailleur clamp bolt by turning it clockwise and adjust the height as necessary. Then, tighten the bolt back up.[4] X Research source This should be done while your bike is on its lowest gear so that there is not too much tension on the inner wire.[5] X Research source Check to make sure the derailleur cage is at the right height. Shift to your middle front chainring and see if

the cage is sitting properly. If not, shift back into low gear and re-adjust the height with the positioning clamp.[6] X Research source Check to see if the angle of the derailleur is parallel to the chainrings. The derailleur cage and the chainrings should be parallel. If they are not, you will have to make adjustments. It is easier to see what adjustments you have to make while you are looking down at the derailleur from above. Envision an alignment between the center of the cage and the centerline of the bike frame. Readjust the bolt to the correct positioning. Loosen the bolt that is attaching the frame of the bike to the derailleur. Shift to the lowest gear of the bike and turn the derailleur to the right position.[7] X Research source Once you have the angle set in the proper place, you can tighten the positioning clamp.[8] X Research source Loosen the front derailleur barrel adjuster. Turn the barrel adjuster completely clockwise in order to release tension in the cable. This can be readjusted later on. Set the inner limit screw to prevent the derailleur cage from moving past the inner chainring. Shift the rear derailleur into the largest cog in the back and front derailleur

into the smallest cog. Using a screwdriver, twist the inner limit screw until the inner part of the cage is as close to the chain as possible without touching it.[9] X Research source You can try spinning the crank to make sure the chain is not catching.[10] X Research source The inner screw of the derailleur is usually the one closer to the frame that controls the lower limit. This screw is sometimes marked as "L."[11] X Research source Adjust cable tension. Loosen the cable that is attached to the derailleur at the anchor bolt. Tighten this cable as much as possible and then make the anchor bolt tight again. It can be helpful to use needle nose pliers while doing this, but you don't have to. Set the outer limit screw to stop the derailleur cage from moving past the outer chainring.[12] X Research source Shift the front derailleur up into the largest chainring and the rear derailleur into the smallest cog. Turn the outer limit screw with a screwdriver until the outer derailleur cage is as close to the chain as possible without touching it. Setting this limit will make sure that the chain does not over-shift and fall out again.[13] X Research source The outer or second screw is the

one that controls how far the derailleur shifts outwardly. This screw is sometimes marked as "H."[14] X Research source Test to see if the derailleur is shifting correctly. Shift through the whole range of gears on your bike. The derailleur should be able to shift into small and large chainrings without rubbing on the chain.[15] X Research source Use the barrel adjuster to tweak the position of the derailleur. Try twisting the barrel adjuster a few quarters of a turn counterclockwise to fine-tune the position.[16] X Research source This will increase the tension so that it shifts into the larger chainring. If you can push the derailleur out, it can mean your cable tension is not right. Turn the barrel adjuster to fix this. Start trimming while you are riding. Trimming means making small adjustments while you are riding your bike. Doing this will help to protect the chain from rubbing against the derailleur.[17] X Research source This will prevent the derailleur from coming out of alignment again. Shimano bicycles come with a half-click on the lever so that you can make these adjustments easily. Ride your bicycle as you normally would. Things should be running smoothly now! If the

derailleur becomes misaligned again, you may have to do a more thorough job in fixing it next time. If you feel like you can?t fix it yourself, you can ask a bike mechanic for help.