Chainline Length?

[big ben]

I'm buying a Howitzer Team BB for my Transition Dirtbag but don't know what chainline length I need, I really don't know what a chainline is. They're available in 50mm and 56mm chainlines...which do I need? I've got a 24/36T set-up, if that helps...

Thanks,
Ben

[Mr. Charles]

i'm guessing that measure ment they are presenting is the distance that the chainring will be from center.

In general, chainline refers to the angle the chain makes when you are in "a gear." Back in the good old days when you had three rings up front, riding in the big ring up front and big cog in back was a sure way to wear your chain out in no time. That was the worst chain line. It put your chain like this:

arial view of bike:
Front
.__
. |
. |/ (chain)

Back

You want a chain line of zero, optimally.
arial view of bike:
Front
.__
. |
. || (chain)

Back

but of course it's impossible have that in all gears.

I am guessing here, but in the context of what i think they mean by 50 and 56mm, you want to have the smallest chainline you can... but if you go too small you'll hit your chain stays with the crank/ring. smaller the number, shorter the spindle, closer to center is the crank.

but like i said, Iam not sure what they mean by 50 and 56. i was just writing to explain what chainline means traditionally. Never heard it in this context.