lockring gap
 

So I have a noname flip-flop hub that was miraculously already on the bike I got for free from a friend's basement. I'm running it single-speed for now, but on the side with the two sets of threads I've got a track cog & a lockring on it. My problem is this: with the cog threaded all the way against the hub and the lockring threaded all the way to where the threads for the cog begin, there's still a 1-2mm gap between the two. I've torqued the lockring as much as I can (and the gap seems to be on the threads that the gear's on) and am wary of flipping the wheel & riding until there's no gap there any more, as I value not busting my ass. Any suggestions, short of Loctiting the thing on there or something?

you can use a bottom bracket spacer (you can get ones as small as 1-2mm) to push out the cog to where the lock ring meets. they are cheap.

Ah, ok.. I didn't realize that a BB spacer would fit on there. Works for me, though if you see me barreling down High St. screaming, you can assume I screwed something up.

What happens if you flip the cog around and thread it on, followed by the lockring?

A BB lockring should work too, in case availability between BB lockring/spacer is an issue. That's what people thread on after the cog in a "bumbike" setup, just put it on inside the cog instead of outside.

I rode that way for a while. I threaded on a BB lockring, then the cog, then the lockring. Worked nicely! Just make sure you get each stage on tight before putting on the next one, a lockring isn't a substitute for properly tightened cogs.

I'm still having difficulty understanding why we still use threaded junctions for rotating parts. I think bikes are the only place this odd practice still happens, every other industry gave it up years ago.. :(

peace,
sam

I did try putting the cog on the other way, but same thing -- it's just not as wide as the threads are on that hub. I might try a BB lockring too, we'll see what I can dig up as far as spacers go. Thanks for the suggestions, all.