So I've got a rear wheel that I want to use on my fixed, and it doesn't have a stepped threading on the hub, it only has enough threading to screw on the cog. I don't know if that means it is supposed to be a freewheel hub or not, but I was wondering this: If I were to utilize the rotafix method to secure the cog, would I be able to safely ride the bike, if I installed brakes? Or would this not be a good idea? I've been trying to find a proper rear wheel, but the wait is killing me, and I really want to go riding soon, though I don't want to get impatient and make a dumb decision that will potentially kill me.
rotafix will get it on there tight enough for you to ride, but backwards pressure will always be dangerous. This will significantly affect the way you ride. Most likely failure situation will be that you start applying backwards pressure, you will feel it slip, and then you must immediately hit the brakes. Worst case scenario is that it will slip backwards until the cog unthreads completely and then will lock up the rear wheel, which will probably end up in a crash. The rear wheel locking up would either throw you over the handlebars (if you're not ready for it) or make you skid out and land on your side. Obviously landing on your side is preferable.
More significantly, converting a wheel meant for a geared freewheel will entail respacing and redishing it, which is a lot of work and could require replacement of spokes. Really, it's not worth the time, money and effort when you could pick up a fixed specific rear wheel for a touch over a hundred bucks. Just go ahead and spend the money.
If you had enough threads to add a lockring (BB lockring, not track, obviously), then with brakes this would be a safe setup. Rotafixed cogs, especially with some loctite, are extremely hard to unscrew, but it is somewhat possible, hence the brakes.
Alright, thanks guys. I found someone who's going to sell me a wheelset for a good price, I guess I'll just be patient and wait out until the weekend when I can pick it up. Thanks for the input, I really appreciate it.