I have square taper crankset from Sugino (compact double 48-34). I am using their aluminium cartridge BB (I think it's 68mm). Anyway, I was wondering what is the difference, if any, regarding the threading between Shimano Hollowtech 2 BB and the Sugino cartridge BB? The reason I'm asking is that I'm considering to change the crankset to the Hollowtech because of the wider diameter of the bearings. I think it's 24 for Hollowtech and 17 for square taper cartridge. And can anyone tell me what is the difference between the "press-fit" BB and the normal BB for Shimano Sora? Can I use either or will only the normal BB fit my frame? Thanks.
The normal threaded, road, Hollowtech II B.B. is designed to fit in a regular 68mm British threaded B.B. shell just like a square taper cartridge B.B. so there is no difference in the threading (1.37x24TPI)
So if you have a 68mm wide threaded shell, the B.B. should go straight in and you can install a Hollowtech II crankset. It’s something I’ve done on one of my bikes.
The difference with PressFit is that the frame does not have any threads in the B.B. shell. Bearings are then pressed into the frame instead and the tight fit holds them in place - so not compatible with a threaded frame. There are lots of slightly different sizes of PressFit bearings, which you could read about, but luckily you probably don’t need to