I think that's a real stretch because it's construction, ratios and target market are so different.

The ACS was a very close ratio hub aimed at the experienced club road racer and time trialer. Construction, based on the racing FC 4 speed, was complex and not overly robust.

The S3X is a wide ratio hub aimed at the current fixie crowd which grew up watching X-games. And old geezers like me who aren't willing to shell out $500 for the real thing. Construction, based on the newest utilitarian wide ratio 5 speed, should be simple and pretty tough. (At least under "normal" use.) The ratios would be pretty useless to today's roadies, who are used to corn cob 10 speed cassettes.

I can't wait to tear into one. But I'm sure it will be more similar to an FW/S5 converted to 3 speed fixed than to an ACS.