How do you read the sidewall of a tire?
On the side of the tire you'll find the size, make, and model of the tire, along with it's maximum inflation and load, speed rating, and safety warnings. Sizing on today's vehicles usually looks like this: P235/75R15 105S (cars) or LT235/75R15 104/101Q (trucks)
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?
We do not recommend using a tire with a speed rating lower than that which the
vehicle manufacturer recommends for the car. By downgrading the speed rating of
the tires, you will reduce the vehicle's handling and control in emergency situations. The industry accepted exception to this rule is that you may downgrade one speed rating level when switching over to snow tires.
What does UTQG mean?
UTQG stands for the Uniform Tire Quality Grades, which the U.S. Government requires on all passenger car tires. The UTQG has three components: a tread wear rating, a traction rating, and a temperature rating. This rating system was developed many years ago so consumers could compare the different qualities of various tires. A standard test tire was chosen and all passenger tires since have been judged against this standard. Typically tires today have tread wear ratings of 200 to 600 (the standard tire was 100), a traction rating of "A" or "B" (on a scale of AA, A, B, and C), and a temperature rating of "A", "B", or "C" to gauge a tire's resistance to heat buildup.
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 right tire typically depends on the primary use of the vehicle, how it is
driven, future plans for the vehicle, the weather, and any special traction requirements.
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 sell four tires or two?
Tire manufacturers and vehicle manufacturers recommend replacing tires in sets of four. (While this may sound like a sales tactic, you can confirm this by checking vehicle's owner's manuals.) When all four tires on the vehicle are identical they perform better for cornering, handling, and tracking. Without this synchronization, the result can be poorer performance and handling which could jeopardize safety. This is especially true when it comes to snow tires. Today's snow tires behave so radically different than conventional all season tires that a vehicle can easily become unstable if you mix two tire types.
If I sell just one or two tires, where should they go?
In the real world many people end up replacing just one or two tires at a time for a variety of reasons. When you are replacing only two tires, make sure the replacement tires are of the same size and construction as those on the car, and preferably identical to the two remaining tires. Furthermore, for safety reasons we recommend you put them on the rear axle, even on front wheel drive cars. If
you are only selling one new tire, it should be paired on the rear axle with the tire having the most tread depth of the other three.
Are winter tires needed?
The answer to this really depends on where the vehicle is located. Premium winter radials deliver state-of-the-art snow traction and exceptional control. Their computer-derived tread designs feature thousands of zigzag "sipes" that provide biting edges for outstanding performance on snow and ice, while delivering a smooth, quiet highway ride. These tires are designed, however, for maximum traction--not long life--so they should be taken off as soon as winter is over.
Should I recommend two or four winter tires?
Today's snow tires behave radically different than conventional all season tires. As such, a vehicle can easily become unstable if you mix two tire types. Therefore, you should always recommend four winter tires.
What does the Mountain / Snowflake symbol mean?
The "Mountain / Snowflake" symbol is a designation that indicates that a tire
has been approved for use in severe winter conditions. The symbol, recently
approved by the Rubber Manufacturers Association, is being phased in over a few
years. Some current snow tires don't yet show it on the tire's sidewall.
How much air should I put in tires and how often should they be checked?
We recommend you inflate tires to the pressure designated by the vehicle's manufacturer. You can find this information in the vehicle's owner's manual or sometimes on the driver's side door jam. The maximum air pressure stamped on a tire may be used under certain circumstances such as when you are carrying a
heavy load, are driving in extreme heat, or pulling a trailer. You should check the inflation pressure of the tires, including the spare, at least once a month and always before extended driving.
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 tires?
To achieve more uniform wear for all tires on the vehicle, tires should be rotated every 7,500 miles or at any sign of uneven wear. If tires show uneven wear, a qualified service technician should check and correct any misalignment, imbalance, or other mechanical problems.
The standard rotation pattern for most vehicles is to move the rear tires straight to the front, and move the fronts to the rear while crossing them to the other side of the vehicle.
We recommend that you rotate tires in the manner suggested by the vehicle's owner's manual.
How should tires be stored during the off season?
Tires should be stored on a cool, dry surface away from sources of heat and ozone such as hot pipes and electric generators. Be sure that surfaces on which tires are stored are clean and free from grease, gasoline, or other substances that may deteriorate the rubber. Tires exposed to these materials during storage or driving could be subject to sudden failure.
What is wheel balancing and how is this different from wheel alignment?
Wheel balancing checks the centrifugal force that will be created by the spinning of the tire to prevent vibrations. This vibration is usually felt on expressways where the higher driving speeds accentuate the shaking. If the vibration is in the steering wheel, chances are the tire that needs balancing is on the front axle. If the vibration seems to be coming from all over, the problem tire is probably on the
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?
You should have a vehicle aligned annually or whenever it starts to "pull" or "drift" to the right or left.
How long will tires last?
The average tire today lasts around 43,000 miles, but like anything else, you get what you pay for. Many are capable of much longer mileage with tread wear warranties at 80,000 miles or higher. Others, such as performance tires, are designed to maximize their cornering and handling capabilities at the expense of tread life and may wear out as quickly as 20,000 miles.
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 tires are worn out?
A tire is considered no longer usable when the tread depth is at 2/32nds of an inch or less. Tires have
tread wear indicator bars within the tread channels that are 2/32nds of an inch high. If these indicators are flush with the surface of the tire, then the tire is legally bald.
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?
Clean punctures in the tread area of a tire should be professionally repaired using the industry standard procedures recommended by the Rubber Manufacturers Association's Technical Publication Number 19. A punctured tire must be dismounted and inspected for signs of internal damage.
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 it's structural integrity.
Why do tires blow out?
There are many reasons a tire can blow out. Usually it is caused from a foreign object impacting the tire, thus causing a sudden loss in air pressure.
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 blow out. This is often noticeable as a slight bulge in the sidewall of the tire.
What should I do if I have a warranty question?
Give us a call! We are here to help you.
Can changing tire sizes confuse a vehicle's on-board computer?
Yes, if you substantially change the overall diameter of tires. Maintaining the original, specified diameters, as closely as possible ensures that on-board computers will function properly and thereby effectively manage such systems as anti-lock braking systems, traction control, fuel management systems, electronically controlled automatic transmission and electronic handling stability systems.
Changing tire diameters sends erroneous readings to the computers. These systems won't fail, but they will be impacted to varying degrees.
Should I be concerned about tire load carrying capacity?
Yes. A replacement tire should always meet or exceed the load carrying capacity of the original.
What might happen if I run tires under-inflated or
Under inflation can cause extreme sidewall flexing. The result may be dangerous heat buildup that can lead to premature tire failure. Over-inflation can cause tires to be more susceptible to impact damage. Furthermore, either condition may adversely affect vehicle handling and tread wear.
What's the difference between an all-season and an all-terrain type tire?
An all-season tire is designed with a long lasting, aggressive tread pattern designed to get rid of water and snow, balancing the wet and snow traction capabilities with dry pavement performance. They generally feature lots of biting edges that enhance snow and wet traction. Most tires with these features are branded M&S for mud and snow.
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 it's rugged edges grip on rocky and uneven terrain.
What is "plus sizing?"
Plus sizing is one of the easiest ways to achieve enhanced performance and change the appearance of a vehicle Converting to a "plus 1" size means increasing the wheel diameter by 1" and selecting an appropriate tire to fit. Likewise, moving to a "plus 2" would result in a wheel with 2" larger diameter.
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.