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The Wheel Truth About Tires

Feb 11, 2015

tire buying tips

We all may have a brand or type that we like… many of us choose our tires based on wheel size and sometimes even season.  Others only get new tires when other tires go flat or a mechanic suggests a new set due to tread wear.  It’s easy to argue that tires may be on of the most complex, most important, least understood, least appreciated and least maintained component on any vehicle.   Today we’d like to uncover some tire myths and give you a better understanding about tires in general that ever driver should know.

What is a tire?  A tire is a flexible container of compressed air. This air container support the vehicle’s load; propels a vehicle forward, backward and side-to-side; stops the vehicle; and cushions the load from road imperfections.  At the core of every tire is an inner liner, as tires are built from the inside out.  The inner liner gives the tire it’s shape and helps it hold air.  Fabric belts are wrapped around the inner tire that are what holds the tire to the wheel.  

On top of the fabric belts are steel belts. These belts have two jobs: They give the tire stability and make the tread pattern as flat as possible. (A flatter tread means more contact with the road.) The tire tread is on top of the belts. There are different tread patterns for different types of tires. The sidewall on the side of the tire gives it stiffness and ride characteristics. A taller, softer sidewall will absorb more bumps, while a shorter, stiffer sidewall will provide better cornering ability and sharper steering response.

On the sidewall of every passenger-car and light-truck tire is an alphanumeric code that describes the dimensions of the tire.  Sometimes the “max load” or “max press” are there as well.  When selecting new tires, it is important to make sure a tire’s load rating is at least a high as the tire you are replacing.

What is the code on the side of the tire?

On the sidewall of your tire, you'll find a code that tells the tire's size and capabilities. Here’s an example:


P195/60R16 63H M+S

    • P - Type of tire (passenger, light-truck, ect) 

    • 195 - Width of the tire across the tread in millimeters

    • 60 - Aspect ratio of the sidewall compared to the width

    • R - Radial construction

    • 16 - Diameter of the rim in inches

    • 63 - Tire's load rating

    • H - Tire's speed rating

    • M+S - Tire is suitable for all-season driving

The tire’s speed rating refers to its ability to dissipate heat, or prevent heat build-up.  As you can imagine, any tire would have to resist or withstand a large amount of heat due to the friction of traveling long roads, at high speeds.  Tire punctures are sometimes more likely to happen on long road trips when tires have been heating up on the pavement for long durations.  A tire with a higher speed rating can dissipate more heat on long highway trips.  So if you like to travel cross country, it may be in your favor to choose tires with a higher speed rating.  

Tires are speed rated from 99 to 186 miles per hour (159.3 to 299.3 kilometers per hour). The most common speed ratings are T (118 miles per hour or 189.9 kilometers per hour) and H (130 miles per hour or 209.2 kilometers per hour). Both of those ratings clearly exceed the nationally posted speed limits and would make excellent long-distance highway tires.

Another important factor in choosing a replacement tire is the load rating. The load capacity number on the tire-size code indicates the load-carrying capacity of that single tire. When selecting replacement tires, consumers have to be careful not to select a tire with a lower load-carrying capacity then is required for their vehicle.  

When choosing your tire, balance for the seasons you do the most driving in.  If you have dry, warm climate all year round, you may be find with a touring tire.  If you live in areas that are colder and consist of a lot of snow or harsh conditions, all weather or winter tires may be your best bet. 

Most consumers will make the mistake of waiting until spring to get new tires. As a tire wears out, dry traction generally increases and wet and snow traction decrease. So the best time to buy new tires is not in the spring, but in the fall.

Where to buy?  Going to the dealership will be the most costly, but they will replace your car with original tires.  Local mom and pop shops tend to have decent prices and will help you find what you need.  You can also shop on the internet but will need to find place to mount and balance them.  

Sizing up your tires:  Some people like to size up their tires.  It involves mounting bigger wheels and tires on a vehicle to enhance the look or improve handling.  Many auto enthusiasts believe the bigger the better but may not even know why.  
Plus sizing usually increases cornering response and traction. Often these gains come at the expense of increased ride harshness. In addition, these larger wheels and tires are often not as durable as OEM wheels and tires.

Before fitting your car with 22”s consider the following: 

    • Make sure that the tire and wheel are approved for use on your vehicle.

    • Make sure that the replacement tire has the same load-carrying capacity.

    • The new wheel and tire combination should be within 3 percent +/- the original tire diameter.

    • Make sure that a new tire placard is installed to inform future owners of the correct tire pressure.

Fuel Economy:  Most people don’t think about this when they choose their tires, especially if you are using price as a deciding factor, but the truth is cheap tires can cost you more in the long run just in gas.  You can see a 15-20% difference in the fuel economy of your vehicle depending on what type of tire you select.  However, since some people look for different performance factors, fuel economy isn’t always the number one priority when designing a tire.   Fuel efficiency can also be impacted by the air pressure inside your tires.  Under-inflated tires will make it harder for the vehicle to be at optimal performance.  

Tire Longevity: Its pretty self explanatory that the longevity of a tire is based on how far you drive, the conditions of where you drive, and how you drive.   Naturally, if you’re doing burn-outs in the local parking lot, your tires will not last that long.  Harsh conditions and poor road conditions will make tires wear out quicker.  

Issues with your car can cause tires to wear out faster.  These include problems with your suspension, shocks, struts, brakes, cv joints and alignment can all cause issues with tire wear.  To increase longevity, get these issues addressed.  

The average mileage for all-season tires is 40,000 to 100,000 miles.  High performance tires tend to not last as long - about 40,000 - 70,000 miles, while top-performance tires won’t even guarantee a tread life.  They usually need to be replaced around 25,000 miles.  

The manufacturer’s estimate on how long a tire should last is based on their testing and not always on real-world conditions. To determine how the tires you're purchasing will wear, look for the tire's Uniform Tire Quality Grading, or UTQG. The UTQG is the U.S. Department of Transportation’s labeling system for the tread wear, temperature resistance and traction of each type of tire.  A tire with a UTQG tread wear of 300 is predicted to last three times longer than a tire with a UTQG of 100. A scale of A to C is used for temperature ratings, and a scale of AA to C is used for traction ratings although ratings and grades may vary from brand to brand.  For this reason, its best to only use them to compare tires within the same brand.  

Rotating your tires is another essential factor to increasing longevity.  It prevents uneven wear to one or more tires, causing it to go bad before the others.   Rotate your tires with every oil change.  

Under-inflated will cause more friction to your tires causing quicker wear down.  Check your tire pressure often.  Also a tire that has low air pressure will lose it’s cornering ability because the sidewall will not be as stiff.   Every ten degree drop in temperature can cause your tire to lose 1 lb of pressure and tires can leak about 1 psi per month due to regular use.  Check your tire pressure often, and especially during the colder months.  

Common Tire Myths: 

1. Are all season tires better than seasonal tires? 

No, not necessarily.  When a tire is designed there is a delicate balance in performance factors.  Essentially, by boosting up one area of performance such as traction for enhanced mobility in rain, snow and freezing temperatures, you are potentially decreasing other performance factors such as handling.  So a seasonal tire, such as a summer tire will definitely out perform all weather tires in it’s season because it’s specifically designed for those conditions.  But on other occasions, it also comes down to quality.  The brand of tire can make a big difference causing the performance to change.  For example, an ultra-high-performance all-season tire may offer better wet-grip than a high-performance summer tire or a grand-touring summer tire.

2. If the tread is good, the tire is good, right?  

No, not always.  Sometimes due to general weather conditions, a tire, even though not driven to it’s mileage limits can go bad and become unsafe, well before it wears down it’s tread.  For this reason, auto manufacturers recommend replacing tires ever 5-6 years regardless of wear.  Tires that are 8, 9 years or older can become cracked, weak, and unconditioned that the slightest issues can cause them to become unsafe.  

To tell the age of a tire look on the sidewall to find the letters "DOT." Following that will be a sequence of numbers, which may be in three or four separate windows. The last four numbers tell when the tire was made: “3112” means the tire was built during the 31st week of 2012.  You also want to check your tires for hairline cracks and deterioration in the rubber.  

3. Your tire will explode if you inflate past the maximum air pressure.  

This one always makes me laugh.  I have seen so many nervous people put air in their tires without a gauge and stress out for fear of over-inflation of the “max load” printed on the tire.  But the truth is - no.  A new quality tire is not going to explode, even if the pressure is exceeded by a very large amount.   However, if the wheel becomes damaged, if its fitted on a poor quality cheap wheel, or if the wheel is already damaged, all bets are off.    

So what do those numbers really mean?  The “max press” number, coupled with the “max load” number (also found on the sidewall), provides the maximum load-carrying ability of a tire.   It's air pressure that allows the tire to carry a load. At 1 pound per square inch (psi) of air pressure a tire can support no weight. To increase its load-carrying capacity, air pressure must be increased. (Imagine a plastic soft-drink bottle: With the top off, it's easily crushed; but when it’s new and unopened, it can support a grown man.) However, at some pressure, adding more air to the tire will not provide increased weight-carrying capacity. That’s what the "max load/max pressure" means.

4. Bargain tires are just as good as name brands if they are made by the same company.  

No.  Just because a brand has produced your tires, you will get what you pay for.  Discount and private brand tires built by big-name companies will resist failures as well as that company’s premium offerings. After all, if the store-brand tire fails, that tire company gets sued just as if the tire boasted a premium brand name. However, things like tread life, traction, ability to resist deep water, noise and comfort will most likely be inferior.

5. Upsizing my tires will cause an inaccuracy in the speedometer reading.  

Yes.  Changing the tire size can also affect your speedometer reading. For many cars, the speedometer reading is based on one full revolution of the tire on your vehicle. If the tire size is changed, then the time it takes a tire to make one full revolution will increase. Since the speedometer rating is calibrated for only one length of rotation, a newer tire that is larger will inhibit the speedometer from reading the correct speed of the vehicle.

6.  The air pressure for the tire is located on it’s side wall.  

Yes, but this is not necessarily the best pressure level for your vehicle.  Unless you’ve changed tire size and type, the proper air pressure for your vehicle and tire combination may be found in your car's owner's manual, on a sticker in the glovebox or affixed to the door jamb.

7. I don’t need snow tires on my 4-wheel drive vehicle. 

False.  A four-wheel-drive vehicle with all-season tires usually is better in the snow than a two-wheel-drive vehicle with all-seasons tires. However most vehicles will perform better in the snow with snow tires rather than with all-season tires. Remember: four-wheel-drive vehicles are great to get you going in the snow, but they are no better than two-wheel-drive vehicles at stopping or turning on snowy or icy surfaces.

8. The tire-pressure monitoring system (TPMS) in my new car makes sure my tires are adequately inflated.

False.   TPMS isn't required to issue a warning until pressure is 25 percent below the vehicle manufacturer's recommendation. That's "well below the pressure required for safe driving," according to AAA and "barely adequate to carry the vehicle's maximum load," says the Rubber Manufacturers' Association. TPMS is intended as a last-minute warning before imminent tire failure, not as a monitor to make sure your tires are properly inflated.

9. When replacing only two tires, the new ones go on the front.

Not if you understand how the tires work.  Rear tires provide stability, and without stability, steering or braking on a wet or even damp surface might cause a spin. If you have new tires up front, they will easily disperse water while the half-worn rears will go surfing: The water will literally lift the worn rear tires off the road.

10. Low-profile tires fitted on large-diameter wheels improve handling.

No.  Not always.  The short sidewalls of low-profile tires enhance the tires’ response when the driver first turns the steering wheel. That gives the driver the (often false) feeling the tire has tons of grip. But after that initial movement, it's the tread compound—the stickiness of the rubber—that determines how well the tire grips the road. Also, the combination of a large-diameter wheel and low-profile tire is usually heavier than the original equipment. This means the suspension may not be able to keep the tire in touch with the pavement.

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