Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
20:1 it's an Italian 36x24 BB. You can measure with 98% assurance of knowing by measuring the width. 70mm would (most likely) be Italian, 68 (most likely) would be BSC (1.370x24).
Measuring width isn't 100% reliable because there are always exceptions, so you can gain assurance by measuring the ID of the thread. If you come up with something close to just under 1-3/8" (or 35mm) it's Italian. If it's about 1mm under 1-3/8" or nearer to 34mm, then it's British.
Another way, if you have good eyes is to look at the thread direction of the right side. (crank side) Italian will have a right thread, BSC will be left hand threaded.
some combination of the 3 three methods will give you 100% assurance of what you need.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance