Do Bigger Tires Improve Performance?

How Tire Diameter Impacts Speed, Fuel Economy, and Power

Speed

One of the concerns drivers have when increasing their tire size is how it affects speed. Before we get to that, we should focus on how it impacts your speedometer. Your speedometer is designed to gauge your speed based on how many times your tires rotate. That means your speedometer will under-read your speed when you install bigger tires than the recommended size. The same goes for smaller tires — you will go slower, but your speedometer will read that you are going faster. If you want to change your tire size, make sure to recalibrate your speedometer so you know exactly how fast you are going.

Not only will you have to recalibrate your speedometer, it will take more power to accelerate, causing your engine to work harder, impacting fuel efficiency, and delivering a slower start to your acceleration.

Fuel Economy

Bigger tires impact your fuel efficiency in a few ways. Bigger tires mean heavier tires, which means your engine has to work harder for a full rotation. That bigger surface area and weight also create more aerodynamic drag, making acceleration slower. While there are benefits to bigger tires for off-roading or aesthetic purposes, driving with bigger tires than recommended will impact your fuel efficiency.

Power Performance

Bigger tires impact your power and performance differently. Larger tires give your vehicle better grip, which is great for off-roading and winter driving. Their extra width and deeper voids also help you crawl over rocks and mud more easily, giving you an advantage while driving off the beaten path.

There are other issues to consider when going beyond recommended tire sizes. With bigger tires comes a higher center of gravity, which increases body roll while cornering. Because of their weight and size, larger tires need more energy to accelerate and slow down. They also lower your gear ratio because the tires have to cover more ground to go the same speed, creating taller gearing. This also impacts towing ability by making your engine work harder.

Pros and Cons of Upgrading to Larger Tires

Upgrading to larger tires will impact how your vehicle performs, with clear benefits and tradeoffs.

Because your speedometer tracks tire rotations based on your recommended tire size, it will need to be recalibrated since it will under-read your actual speed. If you're looking to keep your fuel efficiency, adding larger tires will decrease it because your engine needs to work harder to rotate the tires. Towing and cornering both take a hit too: lower gearing reduces torque to the wheels, leading to sluggish acceleration under load, while the raised center of gravity increases body roll entering corners.

Do Bigger Tires Affect Suspension or MPG?

Oversized tires impact suspension and your vehicle's MPG because your vehicle is designed to perform at its best with the recommended tire size. Installing bigger tires means your suspension has to work harder because of the increased unsprung weight (the weight of parts not supported by suspension: wheels, tires, etc.). This negatively impacts handling, grip, and ride quality, because the suspension has to work harder to control the tires. This extra weight also puts more strain on other suspension components like control arms and springs, wearing down parts and decreasing ride quality.

When it comes to fuel efficiency, yes, bigger tires negatively impact your MPG. Because they are larger and less aerodynamic, they make your engine work harder to turn, which leads to a modest reduction in fuel efficiency.

Tire Size Calculator for Performance Modifications

If you're looking to install bigger tires on your vehicle, there are a few things to keep in mind. It's highly recommended that if you want to go up in tire size, you don't go over 3%. Tires that go beyond 3% of the recommended size will cause your vehicle's speedometer to under-read your speed and put more strain on your traction control and brake systems.