Originally Posted by chore4n
I'm running a stock Truvativ Powerspline BB 68x108 with Truvativ Touro 48t Crankset.
I'd like to replace both.
Would my chainline be affected if I got a BB that is 68x107?
I'm so new to Bottom Brackets, I'm replacing this BB/Crankset because it's a year old.
Or do I need to? I've ridden it hard since last January...
Any suggestions or advice is great help, thanks!
First - why replace them? My roommate rode that crank/bb hard for three years without needing to replace it.
Secondly, this doesn't make any sense:
"Would my chainline be affected if I got a BB that is 68x107?"
Here's why. The spindle of a bottom bracket doesn't affect a chainline alone. It's the crank and spindle put together that determines how far away from the bike's centerline the chainring will be located. That is chainline. Asking if a bottom bracket will do something to your chainline is a meaningless question without saying anything about what crank you'll use.
Don't go out and buy a bottom bracket. Go out and buy a crank, and then buy a matching bottom bracket that will get you near enough to an appropriate chainline.
Some people get all anally retentive about chainlines, but getting within 2-4mm is plenty accurate.