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Wheel Weight & Why It Matters

wheel and tireThere's no question about it—one of the most important parts of any car project is choosing the right set of wheels. First of all, you've got to pick the right style. Do you want vintage rally wheels, classic mag five-spokes, or something more aggressive and modern? Then, you've got to select the right size, and make sure they'll fit properly on your vehicle. However, there's one more crucial point to consider before making your decision—wheel weight.

You may be asking, why does wheel weight matter? Isn't it the same as weight anywhere else on the car? Well, if you ask an engineer, they'll tell you about something called unsprung weight. In a nutshell, this type of weight has a much greater effect on a car's handling, ride, and performance than ordinary static weight. Read on, and we'll explain why.

What is Unsprung Weight?
Unsprung weight is exactly what it sounds like—weight that's not supported by a spring. In the case of a car, it means anything not supported by the suspension system, such as axles, hubs, brakes, wheels, and tires. On the other hand, the car's frame, body, engine, and even the driver would be considered sprung weight (since they're carried by the suspension).

Since wheels make up a large portion of a car's unsprung weight, choosing a light set of wheels is one of the easiest ways to reduce this form of undesirable weight.

Why Does Unsprung Weight Matter?
Unsprung weight has a huge effect on any vehicle's acceleration, braking, and cornering abilities. It's even said that at a drag strip, adding a single pound of unsprung weight to a car has the same effect as adding two or more pounds to the body. Check out the diagrams below to see why it makes such a big difference.

unsprung weightAcceleration
In Fig. 1 above, we see a Camaro with a set of small, light five-spoke wheels. In order to get the car moving, the engine only has to spin 30-pound wheels, so it doesn't have to work very hard. Putting less strain on the engine means faster acceleration. It's that simple.

In Fig. 2, you'll see the Camaro is sporting some bigger, heavier chrome wheels. If you drove the car, you'd notice it feels sluggish, since the engine is working harder to turn the 50-pound rims. This results in slower acceleration and reduced fuel economy.

Braking
Just like the engine has to work harder to get the 50-pound wheels spinning, the brakes also struggle to bring them to a halt. Adding a heavy set of wheels to your car can increase stopping distance, and even wear out your brakes faster than light wheels.

Cornering & Ride
Wheel weight can also have a dramatic effect on handling and ride comfort. Check out the diagram below to see why.

unsprung weight 2

So, let's say you're driving down the road, and you hit a bump. This bump must be absorbed by your tire, wheel, axle, and suspension components. If, as seen in Fig. 3, your car's wheel weighs 30 pounds, 60 pounds of force must be absorbed by your suspension.

In Fig. 4, the wider 50-pound wheels would exert 100 pounds of force on your car's suspension when you hit this same bump. More force passed into your suspension means you'll feel a bigger bump, and your springs and shocks will experience more wear over time.

This same logic applies to cornering, since going around a turn causes the wheels to move up or down as the car leans into the curve. Lighter wheels are also able to "bounce back" faster after bumps, allowing your tires to stay in contact with the road longer, and providing more grip. The end result is confidence-inspiring handling and improved cornering speed.

Conclusions
From NASCAR to Formula 1 to your local drag strip, racers everywhere are concerned with reducing unsprung weight to improve performance. And, even if you're never going to race your car, purchasing a lighter set of wheels can be very beneficial for street driving. So, next time you're looking to buy a set of wheels, take a minute to check how much they weigh—it makes a big difference.

Classic Industries has a wide selection of lightweight factory-replacement and aftermarket wheels. Click here to shop online, or give us a call at 1-800-854-1280.