Billet Aluminum
Billet wheels are very similar to forged as far as strength and weight but are not as common due to the enormous amount of waste created to make a single wheel. If you're after exotic designs, logos or internal patterns for your wheels, billet is your only option. The wheel starts as a solid hunk of aluminum and can be crafted into whatever your imagination can come up with, but it also comes at a price.

Billet wheels gained popularity...

Billet wheels gained popularity in the chopper world.
Forged Aluminum
The most common type of aftermarket wheel is made of forged aluminum because of its high strength-to-weight ratio and relatively low cost. The forged wheel's life starts as a rim blank that is then machined to the desired size and shape by a CNC mill. Most forged aluminum wheels fall in the middleweight class, although there are a few out there that sneak into the heavyweight category due to bolt-on bling and more intricate designs.

Many performance focused sportbikes...

Many performance focused sportbikes use cost effective forged aluminum.
Carbon Fiber
Resting comfortably alone as the lightest wheels available are carbon-fiber wheels. Carbon fiber is very strong and extremely lightweight, but is also the hardest to produce-which makes them the most expensive of the bunch. Despite the significant weight savings over any other aftermarket wheel, they are comparative in strength but dramatically more in cost.

Kent Stotz's 500-plus horsepower...

Kent Stotz's 500-plus horsepower racerruns carbon fiber hoops.
Conclusion:
An aftermarket wheel's styling enhancements alone will change your bike's attitude, and a performance- focused wheel will bring a smile to your face as well. Upgrades aren't cheap. But for knockout looks and a better-handling motorcycle consider it money well spent.