Shimano 105 rear derailleur adjustment

clickrumble

I've just completed a new bike build, all works well apart from an annoying problem with the RD. it's 10 speed triple with 12-30 cassette. I can get the indexing spot on apart from shifting onto the second largest cog, whatever I do it always skips this one going up or down, anyone any clues?

antfly

Try loosening the limit screw.

clickrumble

Thanks, I'm not quite sure what you mean by this though. I have set the high and low limit screws up so that the DR reaches the small and big cogs and have set the indexing so that the gears change all the way up and down smoothly, it just that when going up and down it always skips over the second largest cog, so I don't think it's anything to do with the limit screws. Is it possible I have left the chain too long? When fitting it I measured over the big-big gears but left about 4 links over instead of 2.

sungod

set the chain length the way shimano says in the instructions, otherwise with a triple it's going to be really slack on the granny ring

having shifting issues in one area of the cassette can indicate the mech hanger is loose or bent (or simply that the wheel is not fully seated in the dropouts)

onbike 1939

^^^^^^+1

This usually indicates a RD hanger which is off the plumb position. Check this by sighting from the rear that the Guide pulley is directly under the sprocket bearing the chain.