Flip-flop hub

Occasionally you may find double-sided fixed hubs with stepped threading on both sides, but these are rare and only a few companies offer them.

The lockring is reversely threaded to prevent the cog from coming loose when applying reverse/braking power to the pedals.

Reversing the rear wheel allows switching between Fixed/Free drivetrain, between two different size gears, or both.

Generally, the freewheel is selected to be the same size, or slightly larger (more teeth) than the fixed cog.

Large differences in the number of teeth may require addition or removal of chain links to achieve a proper fit.

ACS makes a special "FAT" heavy duty BMX freewheel in 14T and 16T with 3/16" teeth compatible only with 3/16" chains.

In recent years a few companies have started making 13T freewheels compatible with this thread as well, allowing more gearing options.

In recent years, an innovation in BMX freestyle riding spawned "Left Side Drive".

This component option switches the drivetrain to the left side of the bike in order to move the sprocket and chain out of harms way for riders who prefer to do grinding tricks using the pegs or pedal on the right side of the bike.

Left side drive introduced a different type of flip flop hub for BMX.

These were designed for the use of a drum or disc hand brake on the left side, and a multi speed freewheel on the right.