I have this ubiquitous cheap Wal-Mart bike (http://www.walmart.com/ip/26-Roadmaster-Granite-Peak-Men-s-Bike-Black-Green/45089317z), which has a square taper bottom bracket.
I'm trying to buy a new crankset (http://www.amazon.com/Shimano-Tourney-FC-M131-Crankset-42-34-24/dp/B000F5HXHI), and it requires a 123mm bottom bracket. I can remove my left side crank arm but nothing else, so I'm having trouble guessing the spindle length. Anyone know? It's not listed in the manual either.
The closest approximation I got was by measuring from the tip of the left spindle to the centerline of the bike. That's 82mm. But if you double that, that's 164mm, which seems to be quite a bit more than any bottom bracket that I've seen.