Bicycle Mechanics - Derailler Highs and Lows

I am still trying to get a grasp of how deraillers work. I have always been tempted to screw with the H and L settings and have since learned that this is probablly wrong.

My current thinking is that the H and L settings basically only control the inner and outer travel of a derailler and have nothing to do with shifting. IOW, if the derailler doesn't throw the chain off the innermost sprocket or off the outermost sprocket, than the adjustment needs to be made to cable tension.

Please correct me if I am wrong.

I am still trying to get a grasp of how deraillers work. I have always been tempted to screw with the H and L settings and have since learned that this is probablly wrong.

My current thinking is that the H and L settings basically only control the inner and outer travel of a derailler and have nothing to do with shifting. IOW, if the derailler doesn't throw the chain off the innermost sprocket or off the outermost sprocket, than the adjustment needs to be made to cable tension.

Please correct me if I am wrong.More or less correctomento.But there can be some fine tuning even there.www.parktool has the complete drill on derailer adjustment in the repair section.

I am still trying to get a grasp of how deraillers work. I have always been tempted to screw with the H and L settings and have since learned that this is probablly wrong.

My current thinking is that the H and L settings basically only control the inner and outer travel of a derailler and have nothing to do with shifting. IOW, if the derailler doesn't throw the chain off the innermost sprocket or off the outermost sprocket, than the adjustment needs to be made to cable tension.

Please correct me if I am wrong.

you've got a pretty good basic grasp on the subject, the high limit adjsuts the stop for the derailleur when it shifts to the outter most cog/sproket (away from the frame) the low limit adjusts for the inner most cog/sproket (towards the frame) for the front derailleur when in the big (front) small (rear) gear combo the outer part of the derailleur cage should have about 1mm of clearance from the chain (there should be no rub) when in the small (front) big (rear) the inner part of the cage should have the same clearance without rub. The front should shift faily flawlessly and quickly get into the next gear without hesitation, cable tension fine tunes how it shifts. The rear limits should be set so the derailleur lines up to the cog (i.e. high limit lines the derailleur with the small cog, low with the big) again shifting from the smallest cog to the next smallest should occur smoothly without hesitation, cable tension again will fine tune this change. remember also that a highly tensioned cable can mislead you when adjusting the limit screws, I normally set the limit screws with the barrel adjusters all the way in (turned all the way clockwise.) and go from there....

hope that helps :)

I've got the front derailler pretty well dialed in but i still notice a problem. When the chain is on the second chain ring and the two outer most rear cogs, it still rubs a bit. The strange thing is that it does ok on the outtermost chainring and the outer most cog.

I've got the front derailler pretty well dialed in but i still notice a problem. When the chain is on the second chain ring and the two outer most rear cogs, it still rubs a bit. The strange thing is that it does ok on the outtermost chainring and the outer most cog.

if you reduce the tension in the front derailleur cable, it may solve your rubbing issue, try turning the barrel adjuster clockwise a half turn, if the rubbing continues try another half turn....