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How to Adjust a Rear Bicycle Derailleur

 

jHave you ever had troubles with your bike switching gears unexpectedly or not shifting correctly? Many people have this problem, but are afraid of attempting to fix it for fear of adding to the problem. But you don't need to go into the shop to get your bicycle shifting properly. Just adjust the rear derailleur! A good eye and some lubricant should be all you need.a

Steps 1:Shift the bike to the lowest possible gear (largest gear sprocket on the rear cassette closest to the spokes).b

Steps 2: Look at the rear cogs (sprockets) and make sure they are not touching the derailleur cog/top pulley (guide pulley) when in the lowest gear. This is very obvious as it causes a very loud noise when the bike is being pedaled in this gear.

  • If the cogs are in contact with the cassette, then turn in the derailleur alignment screw ("b" screw or chain gap adjustment screw) clockwise to increase tension until the cogs are separated from the cassette by at least a couple millimeters c

If the cogs are too far from the cassette, loosen the alignment screw until they touch, then tighten it until they just clear a few millimeters.cIf the cogs are too far from the cassette, loosen the alignment screw until they touch, then tighten it until they just clear a few millimeters.d

e

Steps 3: Feel for tension in the lower cable.f

Steps 4: Shift to the highest gear and observe from behind how the chain rides on the smallest cog. If it looks like it might come off towards the axle, tighten the "H" screw clockwise until it looks centered. Likewise, if the chain looks like it's rubbing on the next gear, loosen the "H" screw. To make sure you are adjusting the correct screw, carefully watch the derailleur as you turn the screw, as the derailleur should move with just a fraction of a turn of the correct limiting screw. Then readjust the cable tension until shifting is smooth again.g

Steps 5: Shift to the lowest gear to make sure that the chain does not fall off the cassette. As in the previous step, watch how the chain rides on the cog (this time you're focusing on the largest cog). If the chain seems like it is leaning towards the spokes, tighten the "L" screw clockwise. If it looks like it wants to shift down, loosen the "L" screw. Test your adjustments by shifting through all the gears again.h

Steps 6: Attempt to shift through all of the gears in both directions so you can diagnose whether it is shifting properly. If the bike is having trouble down shifting (shifting to larger rings; chain hugs the smaller cogs) then tighten the cable tension by screwing the tension screw out (counterclockwise) a little bit at a time until it is shifting properly. If the bike is having trouble up shifting (shifting to smaller rings; chain sticks too close to the larger cogs) then loosen the cable tension by turning the tension screw clockwise in a small amount.i

Steps 7: Lubricate the screws and pivot points. Keep the chain lubricated with special chain lube to ensure that stiff chain links do not affect the shifting, and to make sure that the drive train will last.

 

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