Fredo0709

Hi everyone... I've been having a bit of trouble getting the rear derailleur tuned. I have an Ultegra CS-6600 12-27 rear cassette, a compact 34/50T crank, and Dura Ace 7801 shifters.

I don't know if it's my chain length or what but after I set my high and low limits on the rear derailleur, the chain jumps from the 4th to 5th sprocket or from the 5th to 4th depending on which way I'm shifting.

I originally had a 12-25 rear cassette so this didn't happen, I'm at a loss to why it's jumping in the middle of the gear range. Could it be the cassette sprocket spacers? I followed the CS-6600 directions for putting spacers in between each sprocket.

Any insight is really appreciated! Thanks!

Fredo0709

Just in case people are wondering... the cassette is:
12,13,14,15,16,17,19,21,24,27

thanks.

manys

Your indexing is off, which means that while your stops are in the right place the cable length is wrong. This is what the barrel adjusters at the derailleur and downtube are for. This problem is fixed by shifting to the big ring and the smallest cog, shifting up one gear at a time until you hear noise from the chain and gear, and adjusting the noise away. Typically you'll adjust at the derailleur here, then play with the downtube adjusters if you notice any wonkiness on the road. Do this repeatedly until there is no noise as you shift up through the cogs and you can go both ways without problems (use the small chainring when starting from the largest rear cog). It probably sounds more difficult than it is, but it's indeed a pretty difficult adjustment without a bike stand. If you don't have one it may be worth it for you to spend the $50 or so that a shop would charge to do this for you.

Fredo0709

I have a trainer that I do most of my work on. Not ideal but it's better than lifting the bike up. Thanks for the tip and I'll try to take a look at it tonight. I appreciate the response.