Performance Impact of Tire and Wheel Weight
The weight of your track tires and race wheels impacts the handling, acceleration and braking performance of your track car. Heavier race tires and track wheels will require more power to accelerate, more friction to stop, and more force to turn and maneuver your track car. In order to maximize your race performance, you need to minimize the weight of your wheels and race tires while maintaining strength and durability.
Racers initially used magnesium alloy to reduce wheel weight on the race cars of the 1950s, lightweight track wheels have been used to enhance vehicle performance in almost all forms of racing. Most magnesium alloy wheels are too fragile for daily street use and are very limited in their finish options allowing only painting or polishing. In modern times, the most common uses for magnesium wheels are on Formula 1 and GT cars where the race team's continuous monitoring and testing can confirm their strength and durability between events. Fortunately for the rest of us, the wheel manufacturers have also developed lightweight aluminum alloy wheels (see the reference resource on wheel construction for more details on the pros and cons of the most common wheel manufacturing processes) that provide the appropriate durability while they reduce weight.
In order to maximize the performance of your track car, there is more to consider when picking Hoosier race tires and track wheels than just the diameter and design of the wheels that are available. Other wheel attributes that must be considered are width, offset, strength, and weight. A lighter race wheel and track tire will allow you to maximize acceleration, braking and handling performance.
Why does wheel weight matter? Wheel weight, if nothing else, is part of the vehicle’s overall mass that requires energy to convert to motion and speed. Wheels and tires are one of the cheaper and easier items to change on a car, especially when it comes to weight reductions. Wheels can be the source of significant weight savings over oem equipment. Often high quality track wheels and Hoosier tires can provide material weight savings that on a per-pound basis compare favorably to other common parts that are often replaced with light-weight components.
The weight of a wheel is a trade-off between a wheel's bump-following ability and its vibration isolation. The wheel then responds to this force with movement of its own. The amount of movement, for short bumps, is inversely proportional to the weight - a lighter wheel which readily moves in response to road bumps will have more grip and more constant grip when tracking over an imperfect road. A heavier race wheel also exacerbates wheel control issues under hard acceleration or braking as vertical forces exerted by acceleration or hard braking combined with high mass can lead to severe wheel hop, compromising traction and steering control.
The weight of your track car is comprised of two types; sprung and unsprung. Wheels and tires are part of your suspension and are unsprung weight. Unsprung weight is the weight under the springs which moves up and down as the vehicle rides over uneven roads and leans in the corners. Reducing unsprung weight allows the springs and shock absorbers to be more effective in controlling the suspension's movement. Understanding unsprung weight is key to understanding the performance improvements available from lighter wheels and tires.
When your wheel and tire are impacted by variations in the road surface, they transmit those forces into the chassis. If the force of the impact is a 2 G shock, then the chassis will absorb 2x the unsprung weight of the car. If the car has 50 pounds of unsprung weight per corner, than a 2 G shock would transmit 100 pounds of force per corner. That's 200 pounds per axle of force that the suspension must control. Reducing the unsprung weight by 20% would decrease the chassis impact caused by road variations by 40%.
When you reduce the wheel weight, the suspension can more easily bring that wheel back to where it needs to be. In effect, it has a similar effect of fitting stiffer suspension springs or dampers. Handling is all about controlling weight. The lighter your tires and wheels, the easier your suspension can keep the tires planted firmly on the track. Turning a wheel requires torque, lighter wheels and tires require less torque to turn and will generate faster acceleration times while also reducing stopping distances as the brake system will be able to stop the rotating wheels with less force and generate lower operating temperatures.
The easiest way to decrease unsprung weight is to use lighter wheels and Hoosier tires. Lightweight tires, such as those from Hoosier Tires Direct .Com can materially reduce unsprung weight.
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