COG question..not about sizing.
 

So...

Am I wrong in coming to the conclusion there are different COGs for SS and for FG?As in, FG COGs dont work on SS, they only work on FG exclusively and vice versa.

More importantly,
I'm looking to pick up a SS COG 17t, and want to ensure I pick up something that'll work for it, properly.

Any suggestions while I'm at it?

As much as seems some of your guys don't dig on conversions, this will be going on my Peugeot conversion I'm currently in the process of building up as a cheaper beater/commuter (less than 6mi).
Picked it up from a fella who did the ghetto SS and just pulled the shifters off and cut the links down to run it from the cassette to the crank.

Thanks guys!

You're looking for a "freewheel" a cog is just a piece of metal. A freewheel has some sort of freaky and ungodly mechanism that allows you to stop pedaling. I don't know why you would want to do that.

Ahh so my terminology was off as well...gracias.

and COG = center of gravity, cog = round spikey metal plates on your rear wheel.

haha, well maybe I should add a COG question so people aren't so thrown off(COG pun!?) when they click on the thread.

I'm in accounting so I always think COGS = cost of goods sold :P

unless you are buying a new rear wheel, all you should need is a spacer kit. Pull off the gears you don't want on the cassette, add the spacers so the gear you do want is left in the right spot for your chainline and walla

There's a lot that needs to be clarified here.

First, there are cogs for multi-speed bikes as well as track cogs. If you want to convert to single-speed, the first thing you need to do is determine what type of hub you have. Sheldon Brown has a photo to help.

If you have a cassette hub (also known as a freehub), multi-speed cogs have splines on the interior that slide onto the freehub. Removing the unnecessary cogs from your cassette hub and installing spacers for a correct chainline will get you a single-speed setup. If you have a freewheel hub, the entire freewheel assembly threads onto the hub interface. You can remove the entire multi-speed freewheel and thread on a BMX freewheel. If you go this route, you will also need to rearrange the spacers on your wheel's axle and re-dish the wheel to center the rim in the dropouts.

If you're looking to go fixed, you would use a track cog and lockring on an appropriate hub. Typically, track hubs are of a "flip-flop" style, which has freewheel threads on the opposite side. Purchasing a track wheelset is usually the easiest way to convert an older road bike, because you'll spend less time fiddling with spacers and you won't need to re-dish the wheel.

Well, called up the LBS nearest me and they have some 17t freewheels in stock so i'm going to go give them some MORE business.

striknein,
I have a wheelset in mind already which will have the flip flop hub, free/fixed hub set up.
I'm not looking to go fixed yet, just SS. And from what i had been gathering (reason for this thread) the cog/freewheel you use is side specific. i.e. 17t cog would go on the FG side of the hub and a 17t freewheel would go on the SS side of the hub.
Correct? or am I wrong here and you can use the cog on either side of the wheel? FG or SS?

I understand gearing now after reading, and various other little things. Just not quite grasping this...yet.

For your purposes, a cog/lockring would go on the fixed side, and a freewheel would go on the free side. While you can thread a cog onto either side of a track hub, you can't thread a lockring onto the free side, which means as soon as you backpedal the cog will unscrew itself and your bike will explode.

The fixed side of a track hub has two sets of threads. There is a set of right-hand threads that the cog screws into, and then a set of left-hand (reverse) threads that is used to screw a lockring against the cog. As you resist against the pedals when riding fixed, a track cog has a tendency to unscrew itself. The lockring is there to prevent that from happening.

Ok, definitely makes sense now.

As much as I've seen cogs all over various sites, i hadn't seen many (if any) freewheels plaguing the page so it was beginning to make me think cogs were interchangeable on the hub.
Knowledge bomb, dropped.

I think the reason you don't see many freewheels is because there simply aren't many manufacturers making them. Even higher-end BMX wheels use cassette hubs now. Freewheels are more difficult to manufacture, so you won't see as many boutique parts as you will cogs and lockrings. Also, single-speed won't give you mad hipster street-cred, brah.

Shimano, ACS, and White Industries are really the only companies making quality freewheels anymore. I'd avoid anything else.

Yup the LBS has Shimanos and ACSs in store, both sitting at about the same price point so I'll most likely be going with the Shimano.

Hipster cred? Eh, i'll live without it.....for now.
I'll worry about getting my sick sitting down skidzzzz skillz later for the hipster ladiessss.

Much appreciated to all who helped (or replied with what they consider help, haha)!

Looks like you learned a few things today.

I've been on VW forums for 5+ years now, I pretty much know to expect these types of things, haha.