Plus Sizing Explained: A Guide to Upgrading Your Wheels and Tires
Upgrading your vehicle’s wheels and tires is one of the most popular and effective ways to change its appearance and performance. However, simply buying larger wheels and slapping any tire on them is a recipe for disaster. This is where the concept of Plus Sizing comes into play.
Plus sizing is the practice of increasing the diameter of your wheels while simultaneously decreasing the profile (sidewall height) of your tires. The ultimate goal is to keep the overall diameter of the tire identical (or as close as possible) to the factory specifications.
In this guide, we will break down how plus sizing works, why drivers do it, the tradeoffs involved, and how to calculate it correctly.
The Plus Sizing Concept
Plus sizing is categorized by how many inches you are adding to the wheel diameter.
- Plus Zero (+0): You keep the same wheel diameter but switch to a wider tire with a slightly lower aspect ratio. (e.g., replacing a 205/65R15 with a 215/60R15).
- Plus One (+1): You increase the wheel diameter by 1 inch. To compensate, you use a tire that is wider and has a lower aspect ratio.
- Plus Two (+2): You increase the wheel diameter by 2 inches, requiring an even wider tire with a very low aspect ratio.
A Plus One (+1) Example
Let’s look at a practical example of a Plus One upgrade.
Factory Setup:
- Tire Size: 205/55R16
- Wheel Diameter: 16 inches
- Overall Tire Diameter: 24.87 inches
Plus One Setup:
- Tire Size: 225/45R17
- Wheel Diameter: 17 inches (up 1 inch)
- Overall Tire Diameter: 24.97 inches
As you can see, despite moving to a larger 17-inch wheel, the overall diameter of the 225/45R17 tire is only 0.1 inches larger than the original. This tiny difference is well within the acceptable ±3% margin.
Why Do People Plus-Size?
Drivers opt for plus sizing for two primary reasons: aesthetics and performance.
1. Appearance
The most common reason for plus sizing is purely cosmetic. Larger wheels with lower-profile tires fill the wheel wells more aggressively, giving the vehicle a sportier, more modern, and premium appearance.
2. Handling and Performance
From a performance standpoint, plus sizing can significantly improve handling. Because the tire sidewall is shorter, it is stiffer and flexes less during cornering. This leads to:
- Sharper, more immediate steering response.
- Increased stability through high-speed corners.
- A wider contact patch (since plus-sized tires are typically wider), which improves dry grip and braking performance.
The Tradeoffs of Plus Sizing
While plus sizing offers aesthetic and handling benefits, it is not without its drawbacks. It is essential to understand these tradeoffs before making an investment.
1. Ride Comfort
The most noticeable tradeoff is a stiffer, harsher ride. A taller sidewall acts as a cushion, absorbing impacts from bumps, potholes, and rough pavement. When you reduce the sidewall height in a plus-sized setup, there is less rubber and air to absorb these impacts, transmitting more of the road’s harshness into the cabin.
2. Vulnerability to Damage
With a lower-profile tire, your expensive new wheels are physically closer to the road. This makes them much more susceptible to damage from potholes, curbs, and road debris. A severe pothole that a tall factory tire would easily absorb might bend or crack a plus-sized wheel.
3. Cost
Plus-sized setups are generally more expensive. Larger wheels cost more to manufacture, and low-profile, wider tires require specialized construction techniques that drive up the price. Additionally, replacement tires in larger sizes will consistently cost more over the life of the vehicle.
4. Wet Weather Performance
While wider tires improve dry grip, they can sometimes struggle in heavy rain or snow. A wider tire must displace more water to maintain contact with the road, making it slightly more prone to hydroplaning than a narrower factory tire.
How to Calculate Plus Sizing Correctly
To successfully plus size your tires, you must ensure the new overall diameter matches the original. The general rule for a Plus One (+1) upgrade is:
- Increase the wheel diameter by 1 inch.
- Increase the tire width by 10mm to 20mm.
- Decrease the aspect ratio by 10%.
However, estimating can be risky. To ensure safety and accuracy, you should always verify the exact dimensions.
Our comprehensive tire size calculator is built specifically for this task. It allows you to input your factory tire size and compare it side-by-side with your proposed plus-size setup. It will instantly tell you the difference in diameter, width, and how it will affect your speedometer, ensuring you make a safe and stylish upgrade.