Chain Noise and Chain Line Optimizing...
 

I'm wondering how to optimize my chain line...After installing a 56T before nats, I noticed the chain was pretty noisy, so my theory is that my chain line isn't really straight (my perception is that the chainring is slightly outboard from the cog)---and the larger chainring accentuated the friction, because it worsened the angle between chainring contact point and cog contact point.

Is my theory correct, or am I insane. Or, if I'm insane, could I still be on the right track (no pun intended)? :D

I was thinking of experimenting with different thickness shims behind the cog to move it outboard and achieve a straighter chain line. This is what I've done with road bikes in the past.

I'd be measuring the chainline first before you went changing any alignments.

In my own experience, different chainrings, cogs and chains make for different noise levels. Some combos are almost silent, but changing one element can change the noise of the combo. Also look at chain/chainring/cog wear as that can be a logical source of noise.

New chainring + old cog and chain will be noisier than usual because drivetrains wear together. Yes we swap cigs and rings all the time, but if your kit is 5 years old, and you throw a new ring on, then the chain won't mesh properly with the rings teeth.

Sight your drivetrain by looking down your chain from ring to cog when your bike is on a workstand. The ring is a flat (or should be!) so it gives you a reference plane. Your ring and cog should line up. If not, a tooth's width either way is okay. Obviously, the further out from center, the worse/noisier it will be, but 2-3 mm either way should be ok.

I didn't know how to measure chainline, was just eyeballing it, but now reading Sheldon Brown's chainline measuring article. :)
(Any other methods or references you would recommend?)

All new everything, so no wear differences.

All new stuff.

I'm thinking I'd like to make it dead straight, if possible. To me, the noise indicates friction, so if I can get it straight, it should be quieter, but most importantly, a lower friction drivetrain.

Thanks guys, much appreciated.

less noise =/= lower friction. Too many variables.
*it could mean that... if the noise was from a bad chainline... but there are many other reasons a drivetrain could be noisy.

Agreed for sure, I just haven’t made any efforts to make a straight chainline, so it’s a good thing to attempt and learn something new. It might help, or the noise may remain for other reasons.

ahh gotcha.

In track if you're on 1/8 you're probably going to get a lot of noise compared to road/tt. My Izumi stuff is really loud. Some of the Sram is supposed to be quieter. It gets worse after I wax it.

Measuring chainline is a pita on aero frames :D