Originally Posted by
mrrabbit
You are free to argue with Mr. Sutherland, Jobst Brandt, and just about anyone who has been around longer than I have who has been involved in documenting standards and common industry practices over the last 5 decades...those are their numbers...not mine.
Sure you can fudge the narrow 6 on 120-122mm...but "A' is the spec that keeps you out of trouble...that's why I made it clear - the freewheel part is what has to be right - "A".
=8-)
Hillrider is right, 6u or narrow 6 freewheels use 7s spacing and were made to offer 6 gears in the width of 5 for older 120 hubs. 6s or standard 6 has the spacing of 5s and is roughly the width of a 7s freewheel for 126mm hubs. (I've sold enough of these to know, and still have a bunch of 6u freewheels if anyone wants one).
Of course individual hubs may vary which is why I usually tell folks how to measure for themselves rather than publish 2nd hand specs which are prone to misprints and typos.