Summary:
Our father's and grandfathers' wheel covers were gleaming orbs of chrome plated steel, glittering wire spoke patterns, or flat chrome Frisbee look-alikes. Before 1980, chrome plated steel was the only material light and strong enough to do the job. Unfortunately, plated steel thin and light enough for hubcaps was easily dented, and if scratched or driven in winter, i.e., in salt conditions, was likely to rust.
Our father's and grandfathers' wheel covers were gleaming orbs of chrome plated steel, glittering wire spoke patterns, or flat chrome Frisbee look-alikes. Before 1980, chrome plated steel was the only material light and strong enough to do the job. Unfortunately, plated steel thin and light enough for hubcaps was easily dented, and if scratched or driven in winter, i.e., in salt conditions, was likely to rust.
ABS plastic (Acrylonitrile-Butadiene-Styrene) was introduced as a standard material in plumbing pipe in the 1970s, and became the universal material in hubcaps by the mid 1980s. ABS has the attributes of rigidity, strength, and high resistance to salt, chemicals, heat, cold, pressure, and impact. It has excellent resistance to breaking, scratching and chipping, even at low temperatures.
Parts made of ABS plastic weigh only a fraction of their steel counterparts. They can be painted or chrome plated to produce a range of visual effects. Scratches or dings on the surface of plastic are stable, and look the same years later as they did the day the scratch occurred. Whereas, when chrome plated steel is scratched, it will then rust. These qualities make ABS plastic an ideal material for hubcaps, wheel covers, and many other automotive parts.
Today, nearly all wheel covers for passenger vehicles, including original equipment and aftermarket replicas, are made of ABS plastic. In fact, the majority of non-structural auto trim items, including company logos, lettering, grills, cowlings, bumpers, frames, light reflectors, bezels, etc, have been made of (chromed) plastic for nearly 20 years.
One category of modern hubcaps still made of metal is known as 'Wheel Simulators', which are made of highly polished stainless steel. Wheel simulators are designed primarily for the larger wheels supporting heavy utility vehicles, dual wheel trucks and RVs. A few models are available for single wheel trucks and trailers. 'Simulators' are so named because they look like, but they are much less expensive than, chrome plated wheels. Further, stainless steel is highly corrosion resistant, which can not be said for chrome plated wheels.