Originally Posted by grok85
"This is real simple.If he has a shimano 9 speed double octalink crank the 68x109.5 IS correct."
They may be the correct parts but it does not mean he has a good chain line.
How is it that you check chain line? or do you just take what the manufacturer gives you and pray that it works?
All chain widths will not work on a indexed rear cluster. But it I guess that is ok because it was your suggestion.
Well the way to check chainline is outlined at the park tool site. with a double it's from the center of the two rings. Not relative to the small one. I did not say all chain widths.