Sugino Mighty 151BCD JIS?

I have a set of Sugino Mighty 151BCD track cranks. The non drive arm has a JIS logo. Reading on the web indicates that the 151BCD cranks were ISO.

So do I have a mismatching set or is it actually JIS?

That’s a bit weird. My Mightys are 151 and ISO. I know the switch from ISO to JIS was sometime around the 151/144 switch, but man, it was the 70s, anything could have happened really.

Are they also stamped with letter codes? Mine are stamped “F-3” on the drive side, and “76.1” on the other. I also have a 144bcd drive side one stamped “49.8”. No idea what any of that means. You could easily have a mismatched set and not be able to tell.

I’ve wasted a lot of time on this topic in the past, reading the endless ISO vs JIS posts on this forum and others, and came to the conclusion that when in doubt, test it out. Only way to really tell for old parts like those.

I have “75.6” on the non drive side and “F-9” on the drive side. If I buy a BB and its the wrong one will it be obvious if it doesn’t fit? The JIS logo is in the recess to the left of the word “Mighty”.



as per Sheldon, et al, ad infinitum:

  • ISO crank + JIS taper = chainring 3-4mm outboard (noisy chainline)
  • JIS crank + ISO taper = chainring 3-4mm inboard (possibly scrape your cranks on the bb/frame, otherwise noisy chainline)

If it’s just the non-drive that is JIS, who knows. The bike might explode.

I got this reply from a guy on ebay.

I found I got the best
chainline running a 107mm symmetrical JIS (shimano actually) BB. From what
I gather JIS taper is closer to the taper of older campagnolo BB spindle.
This is why Phil Wood recommends JIS taper for older Campagnolo and
Japanese cranks (which were essentially copies and in many cases
improvements off Campy’s stuff). Campagnolo didn’t introduce ISO until the
early 90’s.

I guess the reason why only one of your cranks is stamped
JIS is that it is a replacement for a damaged left hand crank. Non-drive
side cranks do have a habit of loosening if you don’t keep an eye on them.
Hope this helps.