Originally Posted by taras0000

You can't flip the BB as the cups are threaded differently (lefthand/righthand). Flipping the spindle won't work unless it's asymmetrical, which it usually isn't (it's rare if it is, this is usually only done when the BB/rear wheel are offset, like on fatbikes). If it's not exactly 42mm, but your cog is 42mm, then it's near enough that it doesn't make a difference. You can measure this by measuring the flanges on your track hubs, divide by 2 to get flange spacing from the centerline, then add the difference from the cog to the DS flange. Spoke flanges on track wheels are symmetrical. Then if you're the anal type, you can measure the centerline to trackend on each side and see if your wheels are centered, lol.