RD not wanting to shift into lowest gear...
 

disclaimer: bike repair newbie here


bike: 2004 specialized allez elite shimano 105, triple chainring, 9 speed cassette

currently my bike is not wanting to shift into the lowest gear (largest sprocket on the cassette). the chain will hop back and forth from the lowest gear to the second lowest gear when i shift all the way down.

i've adjusted the set screw on the RD to no avail. gears seem to be indexing fine otherwise. does this sound like a bent hangar?

Which screw did you turn, and which way?

You need to check the lower limit screw, which will have an "L" next to it. If you can push the derailleur slightly past the largest cog (but not too far) with your hand or by pulling on the cable then the limit screw is not your problem.

Next check the cable adjustment. With the shifter in the lowest gear, turn the derailleur's barrel adjuster counterclockwise until it makes the shift when you turn the cranks.

If that screws up the shifting at the high end of the cassette then you may need to have a shop check the hanger alignment (after checking the high limit screw). What chainring are you in when you have the problem?

Any derailer adjustments made without first checking proper alignment of the hanger can lead to frustration and mis-diagnosis of the shifting problem. It can also lead to purchasing replacement parts that are not needed and the original problem may not even be improved. Step one to correct shifting problems - check derailer hanger alignment.

i think i'm to the point of having a shop check the hangar alignment. i've adjusted the right set screw, adjusted the barrel adjuster, and when i manually move the derailleur it will get up on the largest sprocket, just doesnt want to get all the way up there using the shifters.

what does fixing a very slightly bent RD typically cost?

let's hope your bike is steel. easy and probably $10