Question about changing flip flop hub gearing.
 

Greetings

When I first bought my fixed gear, it was a 42/16 and had a flip flop hub, but I've changed it to a 44/13 but now I want to change it to 44/16 without removing the 13t cog from the hub so that I'd have easy access to both gearings. Can I just flip the wheel and remove the 16t (coasting side) and replace it with the 16t fixed?

Or do I need to buy new parts like a special hub.

It depends on whether or not you have a fixed/fixed flip-flop hub. A freewheel can be installed on fixed threading but a fixed cog and lockring can't be used on freewheel threading. If your hub is fixed/free, you're stuck with a cog on one side and a freewheel on the other.

If you've got a "coasting side" as you said, then no. Get a chainwhip and lockring tool, buck up and switch 'em out depending on how you wanna ride that day.

Okay, I'm gonna backstep with this question: What makes a fixed gear fixed? Is it the hub, the cog and lockring, or a combination of both

As I said though, just because there's a freewheel installed doesn't necessarily mean the hub is fixed/fixed.

Ooof. True, missed that. Got chased down a ****in* dead end street by an unleashed german sheperd on my ride today, eventually ditched my bike and ran through a field falling into an anthill only to have him try and play fetch with me. Needless to say my brain is a little...uh...constipated.