How 6UL's are made

Gen II 6UL   01/09-

The second generation 6UL wheels are low pressure (LP) cast and T6 heat treated. LP casting refers to the aluminum being forced into the wheel mold under pressure. This pressure eliminates the possibility of bubbles and voids in the aluminum casting. It also compacts the aluminum which allows a higher tensile strength to be achieved with the same material. Gravity cast tooling requires larger wall thickness to allow the molten aluminum to flow into all the small features and crevices of the mold during filling. The design benefit of the new LP technique is that the engineers can optimize the thickness of each part of the wheel without really needing to allow for material flow. This optimization reduces weight without any decrease in strength.

With a gravity cast wheel, the center hub area is the last part of the mold to be filled by the molten aluminum so it is more prone to unwanted porosity or voids. To combat this potential weakness, the hub area is overbuilt to ensure failsafe strength. With the new LP casting, the mold filling and density is the same throughout the wheel structure so the hub area can be further optimized and lightened.

While we kept the same unique 6UL look, the engineers needed to create an entirely new engineering drawing and tooling for the LP casting process. We took this opportunity to reevaluate every single area of the wheel, perform further FEA optimization, strengthened and lightened wherever possible. It takes trained eye and both wheels in hand to spot the differences but there were more than a dozen little tweaks to the Gen II compared to the Gen I.

The end result is a wheel that's about 5% lighter with nearly twice the fatigue life and substantial gains in strength. The Gen II also end up being a bit stiffer and that's directly creates more consistent contact patch loading. Few tuners ever think about this but a wheel that's too soft and flexible will actually deflect under hard cornering loads enough to reduce active camber. Stiff wheels are good.

Gen II's can be identified  by the " 6UL " embossed right on the face of the wheel. The center bore on all versions is 67.1mm, which allows the optional use of standard size hub centric rings.

6ULR 

The all new 6ULR is also be LP cast like the gen II 6UL but features a roll formed or spun forged outer rim or bell. This is a one piece design. The still molten aluminum wheel with it's center section already shaped is then spun. The outer rim is rolled between two mandrels and it's slowly drawn into shape. Imagine how a potter takes a wet clay pot, spinning it on the wheel, pinching the bowl in their fingers, pulling and drawing into its final shape. With roll forming, the outer rim is actually formed under extreme pressure so its a form of hot forging. This pressure further aligns the grain structure in the outer rim area which allows the absolute minimum possible material be used for a given strength target. The mandrels are CNC so an engineer can precisely vary the thickness to a few thousandths of an inch based on the results of FEA (Finite Element Analysis).

Gen I 6UL 01/07- 07/08 (discontinued)

The first generation wheels were gravity cast and T4 solution heat treated. The center bore on all versions was 59.1mm, except the Spec Miata version which was 54.1mm hubcentric. The gravity cast 6UL's proved to have a great strength to weight ratio, particularly at the modest price point. Over the short 18 month production span, countless race wins, TTOD's, local, regional and even a few Nationals Championships were won on them around the world. The ones I feel the most proud of:

• 2008 Champion, Redline Time Attack Mod RWD & overall series co-champion, Matt Andrews, Miata
• 2008 SCCA Runoffs champion, Eric Foss, Spec Miata