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In the 1980s, SSR researched and developed magnesium and titanium wheels in an effort to improve upon cast aluminum wheels that had reached their performance potential. SSR studied the feasibility of bringing magnesium and titanium wheels to the market and found several drawbacks, among them high cost and limited production capacity.

SSR knew, though, that higher quality, lower cost, well-designed wheels were what the customer wanted and in 1991 learned of the advanced technology of semi-solid forging (SSF). This technology was being used to produce parts for the aircraft industry where low weight and reliability are crucial. So, SSR obtained a license to use SSF technology from Alumax Laboratories and after one year of research and development built their now-patented wheel manufacturing plant in Nara, Japan.

The Advantages of SSF

Forging is the process of forcing a solid billet of aluminum alloy between forging dies under an extreme amount of pressure. This creates a finished product that is very dense, very strong. Less aluminum alloy is used to meet the strength requirements for the intended application resulting in very lightweight wheels. The costs of tooling, development, equipment, etc., limit the designs available and usually demand a high price in the aftermarket. Many racers have been willing to pay the premium price required to acquire strong wheels that are lightweight.

The casting process, pouring molten metal into a mold, offers a very reasonable production cost and is a good method for casting designs that are more visually oriented or when reducing weight is not a primary concern. The high heat used introduces impurities into the metals and results in a more brittle, branch-like microstructure that is more susceptible to breakage along its weak points. Cast wheels can be equal in strength to forged wheels but, in order to meet the demands for use on a vehicle, more alloy is used resulting in a heavier wheel. Cast wheels offer consumers the greatest variety of designs at the lowest price and are adequate for most street use applications.   

Casting's Conventional Branch-Like Alloy Structure	SSF's Semi-Solid Globule Granular Alloy Structure

Today, SSR is the only wheel manufacturer in the world to produce SSF aluminum wheels. SSR continues to research ways to further develop SSF, creating beautiful, lightweight and strong wheels that benefit the customer via function and beauty as well as enhanced performance—all at a lower cost than forging or casting.

You can read more about wheel construction, other methods typically used and their positive/negative attributes in our Tech Center.

Trackside with SSR

Billets in heating stage.

The semi-solid billet goes in...

...the formed wheel comes out.

Inspecting a new SSF wheel. The SSF process produces a nearly finished wheel that requires less machining than a typical cast wheel.