Hi I recently fixed an old ten speed bike that I picked up for free from my neighbors and am now looking into replacing some of the old part (pedals, cranks, saddle etc.) but I found out that I need to buy a new bottom bracket as well in order to replace the cranks, which were cottered. I found that they all come in different sizes and I'm unsure how to find the right size for my frame and the crankset I'm looking at.The crankset is an origin8 track crankset and it says that it requires 103-107mm bottom bracket.I looked at some different BB and the had two different measurements. The first was 68mm and the other ranged from 103mm-113mm (something like that.) Anyway. I'm assuming as long I get a BB with the second measurement between 103-107 it'll fit, BUT i don't know what the first measurement means.Any info would be super helpful!Thanks!
There are actually 3 things to look for in a bottom bracket. First is spindle length, your crank requires a spindle from 103 to 107 mm in length. Next thing is bottom bracket shell width and last is the bottom bracket threading. The most common is English threads with a 68 mm bottom bracket shell, but if your bike was made in Italy it could have an Italian threaded bottom bracket with a 70mm bottom bracket shell. Even less common are French threaded bottom brackets found on old French bikes. Italian and English bottom brackets are easy to find, French threaded bottom brackets are very difficult to obtain.
68mm is the width of the bottom bracket shell. The other number is the length of the spindle. If it's not long enough, you won't be able to put the crank arms on all the way. If it's too long, the only repercussion is the pedals will be further apart (called the 'Q' factor.)
