Two years later, the market had fallen to approximately 39 million wheels. “When the crash hit and the mar- ket tanked, 20 million wheels evapo- rated,” Lilley said. In 2011, Lilley estimates the


market will bounce back to more than 49 million wheels. After the closure of the casting assets of three major wheel providers, only about a half dozen cast wheel suppliers remain in North America to meet that demand. Tis means high capacity utilization for the remaining cast wheel providers, but it also means an increase in foreign competition is possible. “Imports have been the biggest


change in our market the last couple of years,” Crick said. “China is the largest exporter of wheels into North America, and it has grown tremen- dously due to low cost supply.”


To Cast or Forge Lilley said that in 1987, instal-


lation rates of aluminum wheels on North American automobiles was 19%. In 1992, it was 35%. In ’97: 49%. Tis year, the number is 73.3%. Aluminum wheels have gone from holding less than one-fifth of the marketplace to nearly three quarters. Te market penetration of alu- minum varies across different types of automotive applications in North America. For passenger cars, which is expected to account for 21.4 million of the total market in 2011, steel main- tains an approximately 35% hold. On trucks, steel’s grip falls—fewer than 20% are forged and styled steel. “Aluminum took over in the early


2000s, when you could really see the progression in trucks and SUVs,” Lil- ley said. “Te OEMs were just putting out aluminum, and you were hard pressed to find a steel wheel. Te mini- vans and crossovers in a variety of sizes have maintained [aluminum’s place] or pushed it up.”


Light-weighting initiatives account


for much of that growth: just as blocks and heads have gone to the lighter material in the face of environmen- tal regulations, rising fuel costs and fuel economy standards, so have steel wheels been replaced. “Even considering any kind of


decorative hub caps, you will see steel wheels on less expensive cars,” Crick said. “Te disadvantage is they are heavier, and they affect handling char- acteristics and fuel economy.” Not all aluminum wheels are


cast. A smaller percentage is forged. Around 70% of aluminum’s 73.3% total market share is estimated to be cast. Typically, the wheels are made in the low pressure permanent mold pro- cess, but other methods also are used. Enkei uses tilt pour permanent mold casting; some others use diecasting. According to Schorn, casting a wheel makes more economic sense than forging, whatever the material. “Forged wheels are typically more


expensive than cast because the process is more expensive,” he said. “Hypothetically, If a cast wheel costs $65, a forged wheel is going to cost $100. You will see forged wheels on designer cars or cars that have heavy load ratings—mostly trucks because of the mechanical properties you get with the forging process.” To wed the mechanical properties


of forging with the design freedom of casting, Enkei has developed a propri- etary hybrid process. “Tat is why we developed flow


forming technology,” Schorn said. “As the diameters [of wheels] have grown, the side walls have shrunk, so that transmits more road forces and the rim has got to be stronger. Flow forming will give you near forged properties in the rim area, which happens to be the weak point.” Light-weighting and economic


considerations aside, the most impor- tant factor in the great shift to cast aluminum from forged steel wheels was aesthetics, according to Lilley. “It was customer demand—looks,”


he said. “People got tired of hubcaps. Tey are a pain in the neck, and they don’t look very good. So when the aluminum prices started coming


32 | MODERN CASTING November 2011


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