Originally Posted by
hueyhoolihan
i think the, as stated previously, that the new chain may be the root cause.
or maybe just the straw that broke the camel's back.
look closely from behind at a chain and examine how and where it flexes, laterally. if on the big, big combo, the chain will lie on the big cog, then bend to the right immediate after leaving the last tooth. it will then remain straight until it reaches the first tooth of the chainring, then it will have to bend back left again so as to lie in line with the rest of the teeth on the chainring. as the distance between the rear cog and the chainring decreases, this becomes more and more difficult. eventually it will refuse to go over the teeth on the chainring. there are many factors involved, including chainstay length, size of rear cog, size of chainring and flexibility of the chain. probably chainring tooth profile too.
anyway, you may have a "perfect storm" of short chainstays, too big cog, minimally beveled and too big chainring, stiff chain and poor chainline. i might try putting on the old chain just to see if it improves things a bit and go from there.
^^^ thought of that too, but had tossed the old chain when replaced with new one.
TA CNCs their teeth and leaves them with very sharply square shoulders and a side bevel is only on the tips. These do not come with any diagonal bevel to assist the chain to drop in between the teeth. I'm pretty sure it's destined for the dumpster once the new rings arrive, so meanwhile experimenting with a flat file and a round file to see if any improvement can be made over the stock shape.
I would really like to find some < 52T 130bcd rings that have a similar inner shape and tooth as the FSA Super Road rings do. Not that I love FSA rings, but I think the slope those have would help. I'll probably do some testing with a Super Road 52/34 combo (similar 18t gap to my current 48/30) to see how that performs.