You gentlemen are all right. I actually have about six different brands/combinations of square taper BBs that I will experiment with. I hope to memorialize that process in a blog post so stay tuned.
Since the drive side cup/BB is the same on the Shimano UN55 for either 68 or 73mm models....they are stealing the cup-only from a shorter 73mm bottom bracket because Shimano doesn't make an off-the-shelf 73mm spindle length long enough for most cranks/this bike. Essentially the adjustable cup from the 73mm variants is "deeper" so that the cup reaches the bearing and fully supports it. On some other brands the adjustable cup doesn't have a lip preventing it from traveling inside the bottom bracket (Shimano does). You can cheat the system this way on other brands and use a 68mm BB in a 73mm shell, but it makes your cranks a little off-center. I also scored a NOS three piece Tange BB that *might* be the right length. All of these different scenarios have to factor in your tire size....the bigger you go, your chainline gets pushed outward which can start eliminating certain crank options. Hopefully I can make all of this easier to understand in pictures....I'm not really doing it justice in writing. Happy Father's Day to all you bike dads out there 😍 Alex Wirth in Rochester, NY -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/a5422e69-81ea-4e8d-92d3-716b3d2013bao%40googlegroups.com.
