Casting is the most economical process for making lightweight custom wheels, and TSW has found it better to use the economy of casting to make wheels in very precise fitments and to exacting standards rather than using more expensive forging, as there is very little difference in weight and performance between cast and forged wheels in regular wheel sizes. Although forging can produce stronger and lighter wheels, there is no reason to pay the extra cost of forging unless you are buying 20" wheels or bigger. For these bigger sizes, the rims of cast wheels get too heavy. A heavy perimeter on a big wheel makes for a "flywheel" or "gyro" effect that makes the wheel want to continue travelling straight on, thus making the vehicle less responsive to steering input and on braking.
TSW has found that rotary forged lips are motivated for its high performance Nurburgring and Interlagos wheels. This process makes the perimeter of the wheels lighter and thus contributes to the responsiveness of the vehicle. These wheels are cast in the same manner as the other TSW wheels, and then put in a machine where the wheel is spun at high speed, while the lip of the wheel is heated and rollers press it against a template machined to the precise shape of the finished lip. The combination of heat and pressure not only changes the shape of the lip, it also changes the metal structure. The forged metal is more resistant to cracking, to impacts and bending forces than cast metal. Thus the "spun" lips can be made thinner and lighter than cast lips without any loss of strength.
The competition experience of TSW has led the company to focus on other aspects of wheel manufacture that produce more performance per dollar spent than the forging process does.
First of all, the molds used by TSW are machined to very exacting measurements, which reduces the amount of machining necessary to finish the wheels. The wheel is close to finished when it leaves the mold. All that is needed before the machining of the bolt pattern, hub bore and finishing, is trimming of a very limited amount of excess metal. For a wheel to perform properly it has to be perfectly hub centric, perfectly round, perfectly straight and perfectly balanced. This is where TSW puts its focus in manufacturing, because no matter how expensive and strong the metal is, if the wheel doesn't measure up to the highest standards in these respects, it will never perform in a satisfactory manner.
All the TSW wheels are precision machined to be hub centric, with an adaptor hub ring supplied for some applications. The TSW wheels produced under brand names dedicated to specific car manufacturers all have perfect hub centric fitment without adaptor rings.
TSW also takes great care to produce wheels that have a perfect offset for each application, as only a small deviation from the offset that the steering geometry is designed for can cause serious steering problems. Where other manufacturers compromise to have the same wheel be an "almost perfect fit" for a wide range of cars, TSW goes the extra mile to achieve the absolutely perfect fit that gives long term satisfaction and long term economy, with superb drivability and tire economy. "Almost perfect fit" wheels can never match the performance of TSW's precision engineered products.
This is why TSW cast wheels perform better than most forged custom wheels, where only the very high end manufacturers are able to afford the perfection in fitments that TSW sees as an absolute necessity. The constantly growing demand for TSW wheels from performance and competition drivers is confirmation of the soundness of TSW manufacturing philosophy.