so i have a single speed bike and i was wondering how i would go about changing it to a fixed gear. do i have to buy another back wheel with a fixed cog, or can a fixed cog be added to my current wheel which is only single speed. help would be highly appreciated.

what kind of threading does your hub have?

the one on the left, the one on the right or both?

Let see...

How was this wheel made into a singlespeed, with use of spacers and a cassette cog?

Or simply threading a freewheel on to the existing hub?

One or the other, you'll most likely need to replace your backwheel unless the hub you have is the same as the picture Henry posted.

well i have a schwinn 3 speed which was converted into a single speed. dont know if thats any help.

take a picture of your rear hub and post it.

You will have to get a new wheel, or a new hub(and most likely new spokes) and rebuild the new hub on the rim. It maybe cheaper to do the second option(definatly would if you build it yourself) but a lot more work, and you wont have the 3speed hub.

just get a new wheel