Ok guys and gals, talk to me about chain lines. Ive been looking at all this 1x 2x 3x recently with a view to getting a new frame up and running as cheapy as possible. I really like the idea of 2×10 but ive read that if I then go 1×10 or 1×11 then this will give a poor chainline. Is this right?

So whats a good chainline? What should I be looking at? In the past ive just banged the BB on and tightened up the cranks and been off. Am I worrying about nothing?

Good info here.

http://www.sheldonbrown.com/chainline.html

It is simple really, there is too much nonsense talked about chainlines .Its about getting the chain in the place of least compromise for the most commonly visited gear ratios you use, closest to a straight line. Once the chain starts to traverse the gears at an angle it starts to loose a tiny bit of efficiency, wear becomes higher and there is a greater chance that it will come off. This is not a big issue these days, drivetrain components are so good.

A triple does give you a less faff route to going 1x as the middle ring position is where the 1x wants to be. Going 1x with a double is possible if you get creative swapping BB spacers, spacing the ring off the crank etc to get the ring back in the middle. You can quite legitimately use a triple crank and just take off the outer ring to give you 2x. At the end of the day just take some time to understand where the compromises are (which is nearly every gear combo!) and think laterally, not literally.

use a triple crank and just take off the outer ring to give you 2x.

That’s what I did on my 301 for 2×10, and replaced the big ring with a bashring. Works perfectly.
If/when I decide to change it to 1xn, I’ll simply fit a N/W ring on the middle position and lose the granny and bash.