[salimoneus]

A topic not often covered when discussing converting or building a 1x drivetrain (1x7, 1x9, etc) is the chainline. At first thought one might think that all you really need to do is line up the front chainring so that it sits about in the middle rear cog, to balance things out. Well that is certainly a practical way to go and would be the standard configuration.

I would however suggest that you take a closer look at your riding style, and see if we can't take advantage of the fact that we have a single fixed chainring up front, that we can shift inward or outward pretty much at will. As opposed to a typical 3x9 where we are really not afforded this luxury.

For example, I'm a bit of a masochist, so I find myself doing a lot of climbing. Most of my "drivetrain abuse" occurs in the lower end of the cassette. Those are the gears where I am applying the most power and doing more shifting under force. So it would benefit me to shift my chainline inward a bit, so that when I'm putting my drivetrain through the worst rigors, I am...

- Allowing the drivetrain to shift more efficiently when I need it most
- Creating less wear and tear and extending the life of my components

So when it's time to pick out a bottom bracket and crankset, consider taking a closer look at what size is really going to offer the greatest benefits and performance for the types of trails and riding style that you prefer. For example using a bottom bracket with a slightly shorter spindle length, or perhaps using a different crank configuration that positions the chainring differently, or even some sort of chainring spacers although less desirable. Also, just because the manufacturer recommends say a certain length bottom bracket for their frame, does not mean it's the optimal size for your particular setup.

 

[Strafer]

You're way overthinking this.
I set mine for the middle and never have any issues.

 

[salimoneus]

You're right in that the standard configuration will work just fine without issues. I just think that if someone really wants to fine tune to another level, it will make a difference. I have noticed slightly quieter and smoother operation in the part of the cassette I abuse most.

 

[dinoadventures]

I'm a bit uncertain about your calculation of those bb spindle lengths. It seems to me you are trying to say something that doesn't make sense about the bb shell width and then carrying the 1. Bottom bracket spindles typically fall between 108 and 122mm. BB shells are typically 68mm or 73mm and that is NOT something you can change as it is a property of the frame.

 

[salimoneus]

I'm a bit uncertain about your calculation of those bb spindle lengths. It seems to me you are trying to say something that doesn't make sense about the bb shell width and then carrying the 1. Bottom bracket spindles typically fall between 108 and 122mm. BB shells are typically 68mm or 73mm and that is NOT something you can change as it is a property of the frame.

Woops, you are absolutely right, I used the wrong numbers to indicate spindle length, which was clearly my intention. Thanks for the correction!