There are many different ways to form a wheel, and each way will affect the characteristics of the wheel. It is all up to the purpose you will be using the wheel's for. Remember, Lighter wheels=less inertia. This in turn reduces the amount of energy to accelerate, stop, and turn. You must also think about width too. You need to make sure you are not in danger of hitting your struts or coilovers, if any. The use of spacers may be needed.

Take Casting for example. Gravity Casting is mainly used for looks, when whieght is not an issue at hand. Aluminum is poured into a mold and is left to gravity to hold it in. These rims will weigh more in relation to their strength.
Then you have Low/High pressure Casting that will apply a varied amoutn of pressure to the mold in hopes of achieving a denser, stronger wheel.
The last casting method is is the spun rim design. It is a process of heating the inital mold, and then spinning and shapeing the "rim" with rollers and other machinery. I think BBS uses this process for their rims...
Aftermarket companies, much like the one's you mentioned will produce forged wheels. These are used by most aftermarket companies because of the strength to weight ratio achieved from the process. Semi-Solid Forging is where aluminum (or a special alloy in higher priced wheels) is technically melted and shoved into a mold at high rates. Common Forging is where a solid peice of billet aluminum is forced into the forging dies under extreme pressure, creating the ultimate in dense/ strong wheels.

Then to make things even more confusing for ya, there are Multi-Peice wheels that incorporate different methods for various parts on the wheel.

J-Linewheels uses a forging and spinning process to create 2 and 3-peice wheels...

Hope that helps.


/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\- Probably my best post ever.