Orbea Enol roadie, Fly Micromachine BMX, Fort Track fixed
A freecoaster is not a freewheel, it is a converted coaster (back-pedal) brake. A coaster brake has a driver and clutch assembly inside the hub shell (the cog mounts to the driver). These are threaded together, so that when the pedals - and thus the driver - are turned, the clutch moves towards the right hand side of the hub. As the inside of the hub and the clutch are conical and serated, eventually the clutch will engage the inside of the hub and propel the bike forwards. If the pedals are turned backwards, the clutch unthreads from the driver and moves to the left of the hub, where it forces two (sometimes three) brake shoes into the indies of the hub shell. This basically locks the wheel solid, acting like a brake. Remove the shoes and you have a freecoaster. The important thing for freecoasters is, as there is not ratcheting mechanism like a normal freewheel or cassette hub, the wheel can roll forwards or backwards without effecting the cranks (in theory; in realitly they often stick or catch). This is very useful for certain BMX tricks, including riding fakie (backwards).
It is also typically only found on flatland bikes as the mechanics of a decent 14mm sealed hub freecoaster has not been perfected yet.
Most freecoasters are not actually converted coaster brakes anymore, but are in fact designed specifically as freecoasters. The brand leading the game right now is Nankai with their techno-lite freecoaster (www.flatlandfuel.com) which is about $100.00.
Advantages of a freecoaster:
1. You can roll forward or backwards on the rear wheel without the cranks moving. While this isn't that big a deal for rollbacks (riding fakie), in flatland, guys do tricks with their body against the frame rolling while the bike rolls back on one wheel, so spinning cranks would hit their leg and could hurt the rider.
2. Gearing is available as low as 11 tooth. Which means that you can run a smaller main sprocket, down to as small as 23 or so tooth. The smaller gearing gives the rider more room to get around the bike.
1. Maintenance: Some will say that freecoasters are 'unreliable' which is not the case with something like the Nankai, but you must regularly pull the hub apart, clean everything, and regrease it. You must have a straight axle. When things start going wrong with a freecoaster, it is because it needs maintenance, not because it sucks. How little maintenance can you get away with? Well, I have a Suntour (old model) which I have not touched at all for about a year now. But, you may need to clean and regrease it about once every six months or so.
2. Unsealed: The freecoaster is unsealed and no good freecoaster has been made with sealed bearings yet. The Haro Turbine/Odyssey/Dans freecoaster all have the same design flaw in the spring that makes their freecoaster very unreliable.
3. Price: Plan on dropping 100 bucks on just the freecoaster. This is a lot more than your average sealed freewheel rear hub.