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
The easiest and surest way is to remove the left cup, and measure and/or thread guage it. That will tell you for sure whether the thread is 35x1 (French/Swiss) or 1.37x24 (BSC/ISO). If it's BSC life is easy, if it's 35x1, you have to toss a coin or do some trial and error removing the right cup to know the direction of threads.
Some brands use markings like rings turned into the face of the right cup to identify the direction of thread on French/Swiss cups. You might check a source like Sutherlands or possibly Sheldon Brown for some guidance there.
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