So just recently finished putting together my cannondale CAAD9. It has dura ace shifters with ultegra deraileurs. The problem that I am having is that if I have selected the smallest cog in the back with the small chainring in the front, the chain would want to climb to the largest chainring on front. The chain rubs against the chainring and tries to climb. My suspicion is that the crankset that I am using is not a 10 sp (the cassette in teh back is a 10sp) but the same happened to a recently finished Jamis with an 8sp cassette and ultegra 6600 crank. In both cases the chains are correct, 10sp and 8 sp. I am missing something, is there a spacer somewhere that I need or need to remove?

Any help is appreciated.

regards,
JIm

Your chainline might be off, but you're also cross-chaining. Although more pronounced in triple fronts, the basic phenomena is there for a double front as well. There's usually no functional need to cross chain, those ratios tends to be available at other gear combos(with straighter chains) as well.

Jim, Avoiding any cross chaining debate... It can be a combination of things. I just cross chained a couple of my bikes on the stand to try and duplicate your results.

The first was the 105 3X8. On the 30 and 13 the chain is quite close to the 42 middle chain ring, but no interferance. The second is a DA 2X9. On the 39 and 12 the chain is just barely not rubbing the 53. Both required some serious FD trim.

My chainline seems as good as can be with the BB length I installed. I think it could be a problem more so between a 53-39 than a 53-42. More knowledgeable folks will reply.

Brad

PS As chainstay length may also be a factor, both bikes tested are C'Dales, a 2.8 and a CAAD3.

Avoid cross-chaining. If everything else is working well then you are good to go.

Guys, thanks very much for your replies. I can live without cross chaining the bike. It just bothered me that my Tarmac (factory) does not do it even when cross-chaining having 53-39 and 10sp in the back.

No worries, no cross-chaining for me.

Regards all and keep pedaling :-)

It's normal for chainlines to vary slightly from bike to bike, even with identical components.