FAQs
How do you read the sidewall of a tire?

The “P” means that the tire is designed for a Passenger car, “LT” for Light Trucks. If you choose to use a P rated tire on a vehicle that originally took an LT, the maximum load carrying capacity of the tire should be reduced by 9%.
The “235” is called the section width and is defined as the width of the tire in millimeters from sidewall to sidewall when the tire is fitted onto a rim of the recommended width. The width of the tread is slightly less than the section width. The “75” is the aspect ratio, which specifies that the height of a tire’s sidewall is 75 percent of its section width.
The “R” specifies that the tire is a radial tire. Most of today’s tires are radials, but occasionally you may see a “D” or a “B” on the tire indicating that the tire is a bias ply tire.
Never mix radial and bias ply tires on a vehicle. The “15” is the diameter of the wheel in inches. The “105” or “104/101” indicates the tire’s load index as established by the Rubber Manufacturers Association.
Make sure that the tire you replace has the same carrying capacity as the one you are taking off. You can do this by using a tire with the same load index, or by checking the maximum load capacity of the tire which is printed in fairly small print near the wheel. On trucks you often won’t see this designation in which case you should look for a load range such as C, D, E, or F.
The “S” or “Q” is the speed rating of the tire, which indicates the tire’s maximum speed. Some common speed ratings are: Q = 99 MPH; S = 112 MPH; T = 118 MPH; U = 124 MPH; V = 149 MPH; and Z for tires that won’t fall apart over 149 MPH. The speed rating is placed just before the “R” on some older tires. You can also consider this rating as a “performance rating” as tires with high speed ratings are built to withstand higher lateral and g-forces, resulting in improved handling even at slow speeds. If you want to improve handling, upgrade the speed rating.
Can I downgrade the speed rating of a tire?
What does UTQG mean?
Unfortunately, this rating system is limited as a comparative tool because the tire manufacturers perform the tests without much oversight from the government. The ratings can be useful to compare tires made by the same manufacturer, but are less useful when comparing one brand to another. Furthermore, there are virtually no “AA” or “C” rated traction tires, so most of the tires are “A” with a few “B” rated tires near the low end.
Which tire is the right one for this vehicle?

The use of various configurations of grooves and sipes in a tire tread affects the tire’s noise pattern and traction characteristics. Typically, wide, straight grooves have a low noise level and good water evacuation properties. Circumferential and lateral grooves work in concert to enhance the tire’s overall performance.
Directionally, the more lateral grooves on a tire, the better the traction. Sipes are small grooves that cross larger tread elements. The more siping a tire has, the better its traction, especially in snow or mud.
Should I buy four tires or two?
If I buy just one or two tires, where should they go?
Do I need winter tires?
Should I use two or four winter tires?
What do the Mountain / Snowflake symbol mean?
How much air should I put in my tires and how often should they be checked?
Check the pressure when tires are cold; that is, when the vehicle has been parked for at least three hours. If necessary, add air to inflate the tires to the pressure specified on the vehicle placard. Since this reading will be most accurate with cold tires, drive to the nearest source of pressurized air whenever possible. Never “bleed” or reduce the inflation pressure when the tires are hot. When tires heat up from driving, it is normal for inflation pressures to increase above recommended cold inflation pressure levels. If you let air out of a hot tire, it will be under inflated when it cools down. Also, use a high quality air pressure gauge to check the tires. Don’t trust your eyes! You can’t tell by looking at a tire if it is properly inflated.
How should I rotate my tires?
We recommend that you rotate tires in the manner suggested by the vehicle’s owner’s manual.
How should I store my tires during the off season?
What is wheel balancing and how is this different from wheel alignment?
A vehicle’s wheel alignment determines whether the vehicle will track straight down the road. If the vehicle is out of alignment, it will cause the vehicle’s tires to wear prematurely or such that they may create a lot of noise.
How often should an alignment be performed?
How long will my tires last?
Other factors–such as how someone drives (easy or hard), where they live (flat or hilly), and road surface (concrete vs. asphalt)–will also affect the longevity of the tires.
How can I tell if my tires are worn out?
If you can’t find these tread bar indicators, you can use the penny test. Insert a penny into the tread of the tire with Lincoln’s head facing down. If you can see the top of his head, then the tires need replacing. However, you may experience a loss of traction well before the tire is completely worn out.
I have a flat tire, what should I do?
We do not recommend plug repairs; they are dangerous and may void the manufacturer’s warranty. We also do not recommend use of an inner tube for the repair of a damaged tire.
A damaged tire is not repairable and should be replaced if:
- It has been punctured by an object in excess of ¼”.
- The tire has a bubble in the sidewall. This is called an impact break and typically occurs when the tire has hit a pothole or other object, pinching the sidewall between the rim and the object, causing damage to the tire carcass. Air pressure in the tire exposes this weakness, causing a bubble where the structural damage has occurred.
- The tire displays a wear ring around the circumference of the sidewall. This sidewall abrasion is typically the result of driving on the tire while it is under inflated or flat.
- The tire has damage to the inner liner. This may include, but is not limited to under inflation wrinkles, rubber fragments, tire dust, or detachment of the inner liner.
- The tire has any bead damage, large punctures, slices, or cuts, or is damaged in any other way which might compromise its structural integrity.
Why do tires blow out?
Sometimes a foreign object impacts a tire and causes a slow loss of air pressure which cannot always be detected by the driver. A tire driven while low on pressure loses its ability to dissipate heat. This heat can cause a thermal breakdown of the tire on a molecular level, resulting in a blowout. Under these circumstances it is often impossible to determine the actual cause of pressure loss.
A tire can also blow out due to an impact it received sometime in the past. An impact break can happen when a tire impacts a pothole or rut in the road. This impact break can be small at first but grow over time and thus eventually cause a blowout. This is often noticeable as a slight bulge in the sidewall of the tire.
What should I do if I have a warranty question?
Can changing tire sizes confuse my vehicle's on-board computer?
Should I be concerned about tire load carrying capacity?
What might happen if I run my tires under-inflated or over-inflated?
What's the difference between an all-season and an all-terrain type tire?
An all-terrain type tire is a light truck tire that has been designed with an even more aggressive tread pattern. This type of tire may be driven on or off the road in virtually any type of weather and road condition. In rain and on mud, an all-terrain tire’s open, self-cleaning tread provides excellent traction, and its rugged edges grip on rocky and uneven terrain.
What is plus sizing?

Note, however, that while the wheel diameter is increasing, the overall diameter of the tire remains fairly consistent (usually within +/- .04 inches) preserving the speedometer reading and gear ratio.
When “plus sizing,” the tire is wider (section width) and therefore has a larger footprint. In addition, the sidewall becomes shorter (aspect ratio) and more rigid. Together, this gives better lateral stability and increased steering response.
How do I know when it is time for brake service?
How can I tell if my shocks or struts need attention?
Symptoms of wear include uneven wear on your tire treads. If your vehicle’s front end dips excessively during sudden stops, they may also need to be replaced. You can check them by pushing down on the front and rear of the vehicle and checking for excessive bouncing.
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