A carefully considered wheel and tire upgrade is the one modification that makes the biggest difference in a car or truck’s looks and overall performance.
A vehicle’s ability to grip a particular surface is what determines its limits of accelerating, stopping and handling. An aftermarket wheel will often decrease unsprung and rotating mass; it will allow the fitment of different tire sizes; and will sometimes even be stiffer than the factory wheel. The problem is, choosing the wrong wheel and tire combo can have disastrous effects on all of these things.
Selecting the best wheel and tire package for your car doesn’t have to be difficult, but it is a process that takes some planning. This article will walk you through it from start to finish, leaning on expert advice from the folks at Mickey Thompson.
Why Should I Upgrade My Tires?
Car manufacturers spend hours staring at multi-axis spider graphs to decide what type, size, make and model of tire is going on each vehicle they sell. Properties like cost, grip, rolling resistance, weight, ride-quality, tread-life, country of manufacturing, consistency of supply, and sometimes even the looks of the tire are all factored in before a company commits to buying sometimes millions of tires.
That means, in all but extreme cases, the tire chosen is a compromise.
According to the experts at Mickey Thompson, one of the first questions that comes up when helping a customer select tires is, “What are you willing to sacrifice?” This is true whether someone is looking at upgrading tires on a Ford Mustang or a Jeep Wrangler.
For example, most customers are, first and foremost, looking for more grip. But adding grip will almost always come at the price of some combination of tread-life, cost and noise. Sacrifice is in order, but the folks at M/T say trading off one or more of those qualities for improved acceleration, handling and braking is worth it for enthusiasts.
Will Different Wheels Improve Performance?
When it comes to wheels, most enthusiasts will prioritize looks. But while a good-looking set of wheels is the fastest way to set your car apart from the rest of traffic, most cars can also see a performance improvement.
Like tires, automakers also compromise on wheel choice.
Wheel width is intentionally narrower than optimal, so the tire’s sidewall takes impacts before the wheel’s lip. The offset, which determines how far the wheel’s centerline is from the face of the hub, is less aggressive than it could be. This is done in order to leave a legally specified space between the sidewall and fender and provide enough room for snow chains.
Aftermarket wheels can minimize those compromises and more.
Lower-trim level cars normally come with smaller diameter wheels than higher spec trims. A larger diameter wheel with a lower profile tire improves responsiveness, as well as opens up more space for upgrading to larger brakes. Additionally, a wider wheel obviously allows the fitment of wider tires.
Most enthusiasts underestimate the importance of stiffer and lighter wheels, but both properties can mean huge gains in performance.
For off-roaders, increasing wheel diameter is less common. Wider wheels with different offsets are used to allow the fitment of taller tires. The experts at Mickey Thompson noted that while a 35-inch tire was once the norm for upgrades, we’re now seeing those in factory fitments. Mickey Thompson’s off-road customers are now looking at 40-inch or larger diameter tires, even for daily-driven vehicles.
Choosing Wheels & Tires
Tires
Choosing the best tire for your vehicle starts with defining what “best” means.
If you’re using it to commute to work during the week and taking it to Cars and Coffee on the weekends, you may not need an upgrade at all. However, if your weekend involves canyon runs in your WRX or rock-crawling in your Wrangler, there are probably better choices than what the factory provided.
Here are some helpful steps to take when narrowing down options for a tire upgrade:
Start with a realistic description of the types of driving you are doing.
Will the tires be used all year in an area that gets near or below freezing temperatures? Will the tires be used in rain and/or snow? Is sacrificing fuel economy, tread life and noise acceptable?
Consider what size tires the vehicle is equipped with now.
Is a larger size necessary, or will a tire more focused on specific attributes supply the desired improvement? Will a different tire size require new wheels?
Define a budget.
It may need to include replacing the tires more often. It may also be necessary to factor in a decrease in fuel economy.
Do your research.
Make sure the make, model and size of tires you’re considering meet the speed and load ratings of your car.
Consult a professional.
Find someone experienced with your vehicle and the type of tires you’re considering, to make sure the tires you’ve chosen will work without issues.
Wheels
If you’re already buying tires, it’s a good time to do wheels as well.
Most of the steps are the same as above, with attention to fitment being even more critical. The temptation is to squeeze the widest wheel, with the most aggressive offset possible – quite often more for looks than performance. However, the weight of a wheel has a huge impact on performance, and for comparable wheels, taller and wider is always going to be heavier.
After figuring out the ideal tire size, determine the dimensions of the wheels by checking the tire manufacturer’s recommendations.
Comparing the new wheel and tire dimensions to what they are replacing, as well as measuring clearances on the vehicle, will help determine the required offset. Again, consulting a professional will prevent future headaches.
Wheels & Tires 101
Tire Sizes Explained
If tire shoppers know anything beyond “round and black,” it’s their car’s tire size. As a refresher, passenger car and normal-use truck tires use a convention of: tire width in millimeters/aspect ratio – wheel diameter.
For example: 275/35-19. This tire is 275mm wide – give or take, since tire measurement isn’t an exact science. Then, the aspect ratio (the second number) tells you the sidewall of the tire is 35% of the tread width. Lastly, the wheel is 19 inches in diameter. To find the total outside diameter of the tire, add 19 inches, plus 2 times the sidewall height converted to inches, since you have sidewall all around the tire.
More serious off-road tires, often referred to as Flotation Tires, use a different convention. A size is represented as: outside tire diameter x tire width, an “R” if it’s a radial tire, followed by the wheel diameter. A 35x12.5R18 is a tire with a diameter of 35-inches, a width of 12.5-inches, radial construction, and for an 18-inch wheel.
You may also see different designations such as LT for Light Truck, XL for Extra Load, or even T for a Temporary spare. After the size, you will normally see a two- or three-digit number followed by a single letter.
The number is the tire’s load rating. That is a reference number which allows drivers to look up the actual load-carrying capacity of the tire to ensure they meet the standards for their vehicle. The letter is the tire’s speed rating. Again, the letter is used to find a value on a chart, which tells you the maximum safe speed for that tire.
UTQG
Created in 1978 by the National Highway Traffic Safety Administration (NHTSA), the Uniform Tire Quality Grade (UTQG) standards are a set of measurements and ratings that consumers can use to compare the quality and performance of tires. They measure three primary aspects: treadwear, traction and temperature resistance.
Treadwear.
The first number is treadwear, or how long the tire is expected to last compared to an industry standard. For example, a tire with a rating of 500 is expected to last 5x longer, a tire with a 600 rating should last 6x longer, and so on and so forth.
Traction.
The first letter is traction. It’s based on the measured coefficient of friction of the tire locked while pulled along a wet surface; not necessarily a real applicable number since the advent of antilock braking systems. Ratings range from AA (the highest) to A, then B, and finally C (the lowest).
Temperature.
The last letter rating is temperature. It measures a tire’s ability to dissipate heat, and is determined during a test that observes at what speed the tire hits a specified temperature. Ratings range from A (highest) to C (lowest).
These standards give consumers something to consult when choosing tires to ensure they select what is best for their vehicle. For example, a person who lives in a rainy climate like Seattle might prioritize traction ratings while someone with a long daily work commute might prioritize treadwear to get the most out of their investment.
In general, higher UTQG ratings indicate better quality and performance, but consumers should also consider their individual needs and driving habits when selecting tires.
All-Seasons, All-Weather, and Winter Tires
When it comes to selecting the right type of tire for your vehicle, it's also important to consider the seasonal conditions you'll be driving in. Manufacturers offer different tire types to ensure optimal performance and safety on the road:
All-Season Tires.
Often referred to as 3-season tires, these are a good option for a large number of drivers. But while all-seasons perform well year-round and in both dry and wet conditions, they’re designed for more moderate weather. That means, you shouldn’t expect optimal performance in anything beyond light snow.
All-Weather Tires.
Designed to perform well in all weather conditions (hence the name), these tires have a more aggressive tread pattern and a rubber compound that stays pliable in cold temperatures, which allows for better traction on snowy and icy roads.
Winter Tires.
If you live in an area with particularly harsh winter conditions, such as heavy snowfall or frequent ice storms, then a set of dedicated winter tires are likely in order. Designed to provide maximum safety and performance, winter tires provide excellent traction on snow and ice. However, they are not recommended for use on dry roads or in hot weather.
How Does “Silica” Fit In?
Tires have come a long way in the last 20 years. Particularly, a compound called silica has revolutionized tire manufacturing, making it possible to increase dry and wet grip along with tread-life, while also decreasing rolling resistance. “Average” tires now have the grip and tread life of performance tires from not too long ago.
Silica is part of a tire compound referred to as a filler. It helps bind the other molecules in the compound together. Unlike past fillers, silica creates stronger bonds. This allows tire tread to be softer, which provides better grip, while the stronger bonds lessen tearing and chunking, which is what causes tread to wear out.
Silica is also more thermally stable than other fillers, meaning tires function better in a wider range of temperatures.