Alloys or steels; what's best for you? Both types have advantages and disadvantages for different types of driving; but in general if you want beauty and performance you want alloy, and if you want tough, inexpensive, ugly workhorses, you want steels.
Alloy wheels are now standard on most cars because they offer both cosmetic and performance advantages. Unlike steel wheels, aluminum alloy can be cast and worked in many different designs, giving cars a much more individual look, and offering owners the chance to customize even more. The aluminum/nickel alloy is much lighter than steel and makes for more agile performance and better acceleration. A car with alloys on is generally much more fun to drive.
Alloys do tend to bend easier than steels under road impacts, and have a tendency to crack if bent too far. To degree to which an alloy wheel is pliable or brittle depends greatly on how much nickel is added to the aluminum to make the alloy – more nickel adds weight and tends to make the alloy more brittle, less means a lighter wheel that is softer and tends to bend more easily. Construction methods such as casting or pressure forging also have an effect on the alloy's strength.
Alloy wheels can be polished, painted, machined or chromed; different finishes should be cared for in different ways. They are also vulnerable to range of cosmetic damage such as curb scrapes, saltwater corrosion and acid cleaners.
The weight of wheels, tires, brakes and rotors is specifically called “unsprung weight” because it is not being cushioned by the suspension springs. Unsprung weight has much more effect on how the car handles than an equivalent amount of weight above the springs, such that even a small change in weight can have large effects.
Steel wheels are heavier than aluminum, so when you put steel wheels on a car that has had alloy wheels, you tend to find that the extra weight dampens acceleration and agility, lowers the car's center of gravity and in general makes it drive more like a tank. Obviously this can be undesirable for summer performance applications, but in the winter the effect can be a significant physical and psychological advantage. Heavier wheels will make tires bite the snow harder, and when driving in snow, having a car with dampened acceleration and agility, an artificially low center of gravity and a sense of solidity and heaviness can be a very good thing.
Steel wheels are significantly stronger than alloy wheels. It takes greater force to bend steel wheels, and it is almost impossible to crack them. Given their usual utilitarian look, purely cosmetic damage is not generally a major issue.
There are wheel covers that you can put on steels to make them look like alloy wheels; they often come on steels sold as OEM choices, and can be found online as well. Wheel covers are fragile, look kind of cheesy, and are most often held on by a spring steel friction grip that has a distressing tendency to come off at inconvenient times and roll away.
Steels are generally only made in 16” sizes or less. There are a very few 17” steels out there, but not a single 18” steel that I know of. I would imagine that an 18” steel would be ridiculously heavy. Consequently, putting on steels will often involve downsizing. Some high-performance cars will not accept downsized wheels because of oversized brake calipers or other suspension issues.
Steels are also usually 75-80% less expensive than alloy wheels, making them great for a second set, and inexpensive to replace if badly damaged.
Thus for many reasons alloys are the only choice when high performance and/or looks are the qualities you need. Steels are generally better for those no-nonsense daily drivers, or for any cars that don't have to look pretty or do fancy maneuvers because they work for a living. They are especially ideal, however, for that extra set of winter wheels.