I've been looking at cartridges to replace my 3-piece bottom bracket, and I'm puzzled by two things:
1. My bike is Italian but with all English threads (a Bianchi Strada). The BB takes cups designed for a 68mm English/ISO system. The fixed cup has left-hand threads, unlike a 70mm Italian BB. But the shell actually measures 70mm. That 2mm difference is no problem with an adjustable BB, but what about a cartridge? I've never seen one in the flesh, so I don't know how the two parts fit together. Will the 70mm width of the shell prevent me from using a 68mm cartridge?
2. With a 3-pc bottom bracket, you pick the overall length of the spindle and also the left/right length. I use a 3N spindle, 32+52+36=120. Going just by overall length, it looks like I would have to take either a 118 or a 122 cartridge. But they don't say how much spindle sticks out on each side. Are they symmetrical? So I should look for a 124mm cartridge? (to get the same chainline as a 36+52+36?)