rtrdpenguin is a mechanical engineering major at North Carolina State University, and spends a lot of time working on his car.
Tires are an often overlooked, but extremely important, part of your car. They are designed to be consumable, meaning tires are intended to be replaced when they wear out. Badly worn tires can adversely affect the handling characteristics of your vehicle, making it dangerous and unpredictable. Keeping your tires fresh, in good condition, and properly inflated is just as important as changing your engine oil! But, when it's time to go buy new tires, there are so many options! How do you know which tires fit? What type of tire is the best? This guide will answer those questions and more.
How to tell if you need new tires
A good rule of thumb for knowing when your tire are in need of replacement, other than the obvious falling apart or going completely flat, is the "penny rule." You simply take a penny, place it upside-down at the bottom of your tire's tread, and if you can see the top of Lincoln's head poking above the tire tread you need to get new tires. Most tires nowadays also have wear bars, which are colored lines that show up when a tire is worn out. Some of them even make an annoying noise when you drive on tires that are worn to a certain point!
BF Goodrich g-Force drag radials
Tires for your performance car
High performance vehicles demand high performance parts to operate the way they were intended to, and tires are probably THE most important part of your vehicle's performance. Horsepower and torque is fine, but what good is it if you can't put it to the ground? When choosing tires for your hot hatch, muscle car, sports car, off-road rig, or even your highway cruiser or grocery getter, it is important to match your tires to your needs and requirements to get the most out of your vehicle.
Tire sizes -- how to read those confusing numbers
The first thing you need to know when you go out to buy tires is the size you need. Tire sizes can be intimidating at first glance -- they are usually printed on the sidewall of tires as a series of letters, numbers, and sometimes slashes. If you have aftermarket wheels or intend to use a lower/higher profile or width of tire, it is especially important to know how to read tire sizes! Most tire shops will have a database of factory tire sizes for various cars, trucks, and SUVs, but the only way to know for sure what tires you need is to match the tire size to your wheels.
Tire size format
Tire sizes are usually displayed in a format like this:
The P simply means the tire is classified as a "passenger" tire. This letter will nearly always be a P for anything normal consumers like us buy.
The 225 is the width of the tire, measured in millimeters. This should be matched properly to your wheel width, which is inconveniently measured in inches. An exact match is not always necessary -- a wheel width of 7" for example can take either a 215 or a 225 tire. In general you want the tire to be relatively flush with the wheel and not bulge or stretch too much.
R16 is sometimes displayed as just a number. The "R" stands for radial, but since nearly all tires are radial some sizes are listed without the R. This number is the inner diameter of the tire in inches, which should correspond to the diameter of your wheels. This number should be an exact match for proper tire sizing!
Tire size quick reference
Load, speed, and other ratings
Most tires will also have another number and letter to the right of the size. This is your load and speed rating:
The number is the load index, which is a number that represents a range of loads the tire is designed to carry. The higher the number, the more weight a tire can support.
The speed rating is designated as a letter, which tells you what kind of sustained speeds a tire is designed to operate at. Going faster than the speed rating of your tires allows is extremely dangerous, so make sure you have the right type of tires before making a trip to the racetrack! Speed rating is also sometimes marked before the "R" in tire size. The chart below, from Dunlop, displays the different speed ratings and their respective maximum operating speeds.
Tires will also usually have treadwear, traction, and temperature ratings. These generally vary from manufacturer to manufacturer, so beware! A Yokohama tire with a treadwear rating of 400 may not actually last as long as a tire with the same treadwear rating made by Goodyear. These ratings are best used to compare different types of tires within a manufacturer's lineup.
Speed rating chart
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Tire Type: Summer, All-Season, Light Truck
Now that you know what tire size and ratings fit your car, it's time to decide what type of tire you want. Three basic categories are summer, all-season, and light truck.
Summer tires are generally high-performance tires designed for only limited use in wet conditions. Driving in snow or ice with summer tires is a no-go. High performance summer tires generally have a lower treadwear rating, so they will not last as long. However, their grip levels are excellent on dry pavement and most of them are Z-rated or higher for high-speed use.
All-season tires are the broadest of the categories. Some of these can be high performance like summer tires, but all all-season tires have to be able to operate under wet and icy conditions to a certain extent. Most people that drive their vehicle every day, year round, should look for all-season tires. They come in a variety of treadwear and speed ratings, and some of the better ones grip nearly as well as summer tires.
Light truck tires are just what they sound like. Most of these are available in larger sizes with higher load ratings for towing and hauling heavy loads. These are generally all-season and some of them are specially designed for off-road use in a variety of terrains.
There are also more specialized tire types, such as snow tires with extra-soft tire compounds for use in the winter, slicks for the ultimate in grip in race conditions, and drag radials for those who need all the traction they can get but still drive on public roads. In general these are available in more limited sizes and cost a bit more than mass-produced tires, but can give you extra, specialized performance.
Keep your tires properly inflated
Tire pressure is something that is overlooked by too many people on the roads. Maintaining proper tire pressure is vital to the longevity and performance of your tires. The maximum pressure of a tire is always printed on its sidewall, and this number should not be exceeded. You should always inflate your tires to the manufacturer's recommended pressure for normal driving, but to squeeze some extra performance out of your tires you can adjust the pressure up or down a little bit too.
Lowering tire pressure will allow the tire to conform more to the ground and spread out a bit, increasing grip. This is why drag cars have such large tires at lower pressures -- the sidewall can flex during hard acceleration and provide extra grip. Be careful though, if you lower your tire pressure too much your vehicle will get worse gas mileage and have sloppy handling. The worst case scenario is that your tires have such low pressure that the tire bead unseats from the wheel surface all the air escapes!
Higher tire pressures will expand the tires out more, bulging them like a bicycle or motorcycle's (but not nearly as much). You can get some extra gas mileage by upping your pressure a couple of psi because your contact patch decreases, reducing the friction between your tires and the road. Make sure your pressure doesn't go above the maximum pressure listed on the sidewall though!
Tread compound and design
Tire compounds and tread patterns are usually of little concern to the average tire buyer, but for those looking for performance they can give you a bit more bang for your buck if you know the basics.
A softer tire compound generally wears down faster, but gives better grip. Researching different manufactuers' materials used for their tires and listening to the experience of other performance tire users is the best way to decide which ones are best.
I personally run BF Goodrich g-Force Sport summer tires on my vehicle for normal road use because it has a decent treadwear rating, a speed rating of Z, and good predictable grip characteristics for a non-race tire at a very reasonable price. Being a college student, I can usually avoid driving in the rain by using other modes of transportation when it is wet, but driving slowly with these tires in damp conditions is not too much of a problem. Finding the right balance between price, grip, and treadwear is the most important thing to me when choosing a street tire and so far the g-force is my favorite.
Tread patterns are somewhat important to performance, but most of them are designed to work the same way. The tread channels water and debris from the inside to the outside of the tires so you can keep a good contact patch with the road at all times. The most important thing about tread patterns is that some of them are directional, meaning they cannot be rotated diagonally to even out wear like non-directional tires. Directional tread patterns should in theory have slightly better channeling properties.
I am not a tread pattern expert though, and honestly the difference is hard to tell. The thing most buyers will look for in a tread pattern is appearance. The Goodyear F1 is a great performing tire, but I suspect its aggressive v-shaped tread pattern also attracts buyers to a certain extent. Prettier tires will help enhance the look of your car when it's sitting in the parking lot, but it is up to you if a nicer look is worth paying extra or losing a bit of performance for.
But which tires are the best?
Even after all this information, you're probably still wondering, "which tires are the best?" The answer varies depending on your needs, and the only real way to find out is to try tires out yourself. However, this is an expensive and time-consuming process (if you use the tires to their full extent before getting new ones), and you need tires now!
Luckily, there are a number of good resources out there. Believe it or not, performance enthusiasts actually review and discuss tires on the internet quite often. A great resource is www.tirerack.com, a tire retailer that has a great selection and an extensive review database for all sorts of tires. They can also ship tires to local shops for installation, mounting, and balancing, and sell aftermarkte wheels, brakes, suspension components, and other related products too.
A lot of magazines also test tires, such as Consumer Reports. However, in my opinion, the best way to find out what tires are good for you is to ask around and see what other people have had success with. The guy behind the counter at your local tire shop sells tons of tires and will know what to recommend based on your requirements too.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.