My old Schwinn says on the side of the cranks “1/2”. I assume this means that the pedal size to be used would be half an inch. However, only a standard 9/16" wrench will fit on them, yet it wiggles around a bit. Neither a 1/2" or 9/16" will fit on my Odessey Twisted pros. What size are they? It probably has something to do with me not using “pedal” wrenches, but it hasn’t ever seemed to be problematic. Should I just use a crescent wrench or what?
Help please?
Try a 15mm wrench. I think all unicycles use 9/16" pedals but you need a 15mm wrench to tigten them. I’m not really sure why this is someone else might though.
Chex
The 1/2" and 9/16" refers to the thread size and not the size of pedal wrench needed. The 1/2" and 9/16" pedals use the same size pedal wrench.
My Schwinn giraffe uses 1/2" pedals. Some of the older Schwinn standard unicycles also used the 1/2" size. Almost all other unicycles use the 9/16" size since it’s stronger.
Pedal wrenches are either 15mm or 9/16". The 15mm size is much more common. see <http://www.parktool.com/tools/PW_3.shtml>
my undersatding was that: 1/2 inch pedal should use a 9/16 wrech, and the 9/16 peadal, should use a 15mm. But since the 15mm wrench is slightly larger than the 9/16wrench, the 9/16 wrench c’ant be used to take off 9/16 pedals, but the 15mm wrench CAN be used to take off both, but it will have a little extra “play” in there. Finally, the odysses come in both sizes. The way i quickly find out, is the 1/2 inch usually has more threads than the 9/16, or at least it looks like that.
good luck, unless you have really, really short cranks, the 1/2" probably IS refering the the pedal size. 
-Ryan
what do you mean by perferred pedal size? I bet you dont even have a pair of 1/2 inch pedals on any of your unicycles, excuding possibly a girraffe that you may or may not own. for bikes the general rule is 1 piece cranks use 1/2 inch pedals, and 3 peice cranks use 9/16 pedals. of course there are exceptions.
I have Odyssey Twisted Pros and I use a 5/8" wrench on them, which is 15.875 mm
I have purple 1/2" pedals off a little girl’s bike. 
Just use an adjustable wrench