I recently bought a Mark V complete from IRO with the standard wheelset. I noticed that the non-drive side of the hub is threaded. Can I add another fixed cog to this side and use the wheel as a flip-flop? And if so, is there some reverse-threaded voodoo sh#t going on that I should be aware of? Thanks.

my iro flip flop is a fixed-free hub, meaning one side has a reverse thread for a track lockring and the other side does not. this other side is designed for a bmx type freewheel. i wont tell you that you can't put a track cog on there, but you can't screw a track lockring on, and therefore many would consider it a bad idea. do a search for "suicide hub" if you want to know more.

the advantages of running a brake are never more evident than when you're relying on glue/friction to stop your bike.

I have the same hub. Like the previous post says.. flip flop = ss freewheel on one side and fixed on the other. You can go fixed on both but will have to lock down the cog via rotafix and bb lockring/loctite.

Do a search on google for rotafix.

IRO also has Fixed-Fixed hubs. The OP has to look at the hub and say if it is fixed-fixed or fixed-free.

OP?

yeah, a while back I ordered the flip flop wheelset and got a fixed-fixed hub, so, if it has two different size threadings than you are good to go with a fixed cog but, if it only has one size threading then a freewheel it is.

I'm not sure, I just ordered a standard build from the website. Is there some way I can tell by looking at the hub?

yes. the threads on this hub are for a fixed gear. if you look close you can see how there's "two levels" of threads. also, look at the threads themselves (on your hub)...if they all go the same direction (spiraling around the same way) then they're not made for fixed but for a freewheel.

here's another picture where you can see the "levels" especially on the right side:

here's a good picture of regular freewheel threading:

here's a picture of the internal anatomy of a monkey!