How Wheel Weight Affects Your Vehicle Performance
To understand how wheel weight affects your vehicle's performance, you should know how a vehicle is engineered. Your UTV's weight falls into three categories:
Sprung Weight / Mass
The sprung weight is the total weight of all parts supported by the suspension. These include the engine, exhaust system, body, and interior.
Unsprung Weight / Mass
The unsprung weight is the total weight of parts not supported by the suspension. This includes the suspension, axles, braking system, and wheels and tires. Unsprung weight directly affects driving feel. Less unsprung weight lets the suspension stabilize the vehicle more effectively on uneven roads. Reducing unsprung weight improves handling and feel.
Rotational Weight / Mass
There is also the vehicle's rotational weight, which includes parts that rotate, such as drive shafts, wheels, and tires. Rotational weight plays a significant role in performance. Lower weight in these parts requires less energy to accelerate and decelerate, which enhances performance. The further the weight is from the rotational axis, the greater the negative impact. A wheel with more weight around the outer edge will perform worse than a wheel of the same weight with most of the weight closer to the hub.
Cutting weight from your wheels is not just about removing weight, but also about where that weight is located and how it affects your wheel's behavior. If performance is your goal, upgrading to lighter wheels can be worth it.
Rotational Inertia
Rotational inertia is resistance to a change in velocity. A wheel with higher rotational inertia needs more power to start moving than one with lower inertia. Rotational inertia is directly related to wheel weight, but heavier wheels do not always make a vehicle slower.
Rotational inertia is greatly affected by how wheel weight is distributed. Weight centered closer to the hub results in much lower rotational inertia than the same amount at the rim or lip.
To understand rotational inertia, imagine spinning a small weight on a string. If the string is only a few inches long, it is not difficult to get the weight moving. If the weight is at the end of four feet of string, it becomes much harder to spin.
The effect of wheel weight on performance
As a rule of thumb, to improve performance, reduce the weight of your vehicle's unsprung parts. This applies to any car and is usually one of the first areas people focus on for immediate results. Wheels are the easiest and most cost-effective way to reduce unsprung weight, compared to replacing expensive components like axles, wheel hubs, control arms, and driveshaft parts.
There is a lot of physics involved in unsprung weight reduction, but generally, any reduction makes it easier for the suspension to work effectively. Reducing wheel weight in a performance vehicle, especially one meant for cornering, means you will quickly notice better handling. Less mass in motion also leads to improvements in acceleration and deceleration times.
What wheel weight means for braking
Rotational inertia affects braking much like it does acceleration. However, it is usually the mass that has the greatest impact on a vehicle's ability to stop, not inertia.
The effect of wheel weight on fuel economy
Because wheel weight is rotational mass, its effect on fuel economy is not straightforward. If you do a lot of stop-and-go driving, such as rock-crawling, you might see a drop in gas mileage when you reduce wheel weight. You use more energy to get your UTV moving again each time you stop or slow down.
If you mostly accelerate hard and drive at wide-open throttle, you are less likely to see a significant impact. Once heavier wheels are in motion, the vehicle does not work as hard to keep them at speed.
UTV Wheel Construction Methods
The popularity of alloy wheels has increased since the 1980s. Alloy wheels are considered an upgrade over standard steel wheels, and production practices have evolved. The three main construction methods for lightweight wheels are casting, flow forming, and forging. Cast wheels offer the most style options. Flow-formed wheels are lighter and stronger than cast wheels, but more expensive. Forged wheels are the most costly because of the complexity and time required for manufacturing.
Casting – Aftermarket wheels are most commonly cast using a blend of aluminum and nickel. The material is heated to high temperatures, melted into a liquid, poured into a mold, and cooled, creating a lightweight, durable wheel. The wheel is then drilled to specifications and finished with paint or powder coating.
Flow Form – Flow-formed wheels are cast like other wheels. After casting, the wheel is reheated, and the barrel is pulled down and widened by spinning discs. This strengthens the aluminum while using less material than a fully cast wheel. This can reduce weight by several pounds on larger wheels (18 inches and up), but on smaller sizes (14 to 17 inches), the minor weight savings rarely justify the extra cost.
Forged – The most intricate and expensive process, forged wheels are made from a solid aluminum monoblock. The monoblock is heated and pressurized to form the wheel shape. Once formed, the wheel is lathed and CNC-milled to remove excess material. This creates a lightweight wheel that is about three times as strong as a standard cast wheel. The price is also about three times higher than a standard cast wheel.
SO....DOES A LIGHTER WHEEL MAKE A DIFFERENCE?
Bottom line, when installing heavier wheels, you are adding unsprung and rotational weight to your vehicle, which will have a more adverse impact on its handling and performance than any other similar weight added elsewhere.
In conclusion, it's always better to install lightweight wheels when replacing factory wheels. Try to match your stock wheel weight; lighter than stock is always better. Running wheels that are heavier than your OEM stock will always negatively affect your vehicle's performance.
