Plus Sizing, the process of changing wheels and increasing the diameter, is a great way to enhance the look and performance of your vehicle. What is plus sizing and how does it work? This involves changing the tire and/or wheel size from the original size in a controlled manner so as to maintain certain critical dimensions.
When creating a Plus Size fitment, the section width of the tire increases and the sidewall height decreases. The contact patch of the tire changes shape by becoming shorter and wider. While the shape changes, the size (area) of the contact patch remains relatively unchanged.
- High aspect ratio = tall and narrow contact patch
- Short aspect ratio = short and wide contact patch
What does this mean?
The tread blocks with a taller, narrower profile have more deflection than tread blocks on a lower profile tire. Less deflection results in more cornering force and capability. This assumes all other things are equal, i.e same tread compound, design, etc. Installing a Plus Size Tire & Wheel Package changes the shape of your contact patch, resulting in improved cornering, improved steering response and a decrease in ride comfort due to the shorter sidewall.
What is arguably the most common misconception when looking to increase wheel diameter is this also increases the overall combined diameter of the wheel plus the tire. A proper Plus Size will account for the additional wheel diameter by decreasing the sidewall of the tire. The result is little or ideally no increase in overall combined diameter. Maintaining the proper load capacity must also be considered.
Here is a very broad overview of the most common Plus Sizing scenarios. For help with your specific application, contact a sales specialist for assistance.
Plus Zero - Increase the section width while maintaining or decreasing the aspect ratio. The wheel size stays the same so you will not have to purchase new wheels.
Plus One - Increase the section width, in an increment of 10, while decreasing aspect ratio. You will also increase the wheel size by one inch. The result is approximately 1/2" less sidewall on the tire while maintaining a very similar overall diameter. This keeps the speedometer, odometer and other systems that monitor wheel/tire rotation rates functioning normally.
Plus Two, Plus Three, etc. - In each of these cases an additional inch of wheel is added while decreasing sidewall height on the tire. Vehicle design will limit the maximum wheel size.