Tire Terms

A Big O Tires Technician Helps You Learn to Speak 'Tire'!

Aspect Ratio
The ratio between tire height and width.

Asymmetric
A tread pattern in which opposite sides of a tire’s tread pattern are not identical.

Backside Setting
The distance from the mounting surface of the wheel, which contacts the hub, to the back rim flange. It is sometimes referred to as the backspacing or backside measurement.

Balance
The even distribution of weight on a mounted wheel and tire.

Bias-Belted Tire
A passenger type tire which has two rubberized plies of cords which are crossed over one another at an angle (on a bias) plus two reinforced belts which encircle the tires under the tread.

Block-tread Design
A tire tread pattern made of raised rubber compound segments.

Carcass
The portion of a tire that is the foundation for the tread, belts, bead and sidewall.

Casing
The structure of tire cords locked around wire beads.

Compound
The general term referring to the chemical formula for the tread material.

Grooves
Circumferential channels between the tread ribs of a tire.

Hydroplaning
Loss of traction at high speeds caused by a wedge of water that lifts a tire off the road surface.

Load Rating
The maximum weight that the tire is designed to carry; dictated by the tire's construction. Metric passenger type tires are offered with a Standard Load Rating (up to 35 psi), or Extra Load Rating (up to 41 psi). LT Metric (truck type) tires are offered with ply ratings of C (8 ply), D (8 ply), and (10 ply) and at various inflation pressures up to 80 psi.

Nominal Ring Diameter
Diameter of rim seat supporting the tire bead. Examples: 13", 15" and 16.5".

Overall Diameter
The diameter of the inflated tire without any load.

Overall Width
Maximum width in cross-section of the unloaded tire including protruding side ribs and decorations.

Ply
A layer of rubber-coated fabric or wire making up the tire casing.

Positive Offset
A condition where the wheel's mounting surface is closer to the street side of the wheel; when the mounting surface is outboard the wheel's centerline.

Radial Ply Tire
A type of tire that has one or more rubberized plies of cords running from bead to bead (at right angles to the tread and parallel to each other), plus two or more plies of reinforced belts which encircle the tire under the tread.

Ribs
Part of a tire tread pattern created by grooves that run circumferentially around the tire.

Section Height
The distance from rim seat to outer tread surface of an unloaded tire.

Section Width
The linear distance between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations).

Series
A numerical representation of a tire's aspect ratio; for example, 50 series.

Shoulder Blocks
Raised rubber compound segments on the part of the tire tread nearest the sidewall.

Sipes
Slits in the tire tread. Small cuts in the surface of the tread to improve traction.

Steel Belt
A belt material used in radial tires. Its high stiffness provides good handling and low treadwear.

Tire Profile
A term representing the portion of a tire measured as its aspect ratio or series.

Tread Blocks
Raised rubber compound segments on the outside visible part of a tire.

Tread Width
The portion of the tread design that comes in contact with the road.

Unsprung Weight
The total weight of the automobile's components not supported by the suspension system; wheels and tires are prime examples.

UTQG
The UTQG is a 'user-friendly' way for consumers to understand basic tire specs. It stands for Uniform Tire Quality Grade. It's a government-mandated tire rating system based on a tire's performance in treadwear durability, traction and temperature resistance. UTQG ratings are branded on the tire's sidewall.

Varied Pitch Ratio
Variations of angles and sizes of a tire's tread elements that reduce ride noise levels.

Low Profile
A term describing a tire with a low relative aspect ratio or series classification (short sidewall, wide tread).

Speed Rating:

The speed rating is a measure of what speed the tire can safely maintain for sustained periods of time. A higher speed rating will generally indicate that you will have better control and handling characteristics. Speed rating standards are established by the U.S. Department of Transportation (DOT). Manufacturers assign speed ratings to tires after extensive performance testing. On the sidewall of every tire, you’ll find one of these speed rating codes:

M – Up to 81 mph
N – Up to 87 mph
P – Up to 93 mph
Q – Up to 99 mph
R – Up to 106 mph
S – Up to 112 mph
T – Up to 118 mph
H – Up to 130 mph
V – Up to 149 mph
W – Up to 168 mph
Y – Up to 186 mph
Z – (See Below)

What does ‘Up to 99 mph’ really mean?
Tires with a Q speed rating can safely sustain speeds of up to 99 miles per hour. The tire may be able to reach higher speeds, but traveling at speeds higher than 99 mph for any length of time would be unsafe - the tire is not designed to handle it.

What is a Z Rating?
For tires having a maximum speed capability above 149 mph, a Z rating may appear in the size designation ...above 186 mph, a Z rating must appear in the size designation, including a Y speed symbol in brackets.

A Few Tips About Speed Ratings…
Never mix tires with different speed ratings, as this may cause serious handling problems.

We don’t recommend downgrading the speed rating of your tires, as the vehicle manufacturer has done extensive testing to determine which tires match the various driving characteristics of the vehicle. However, if you are looking for better handling, there is generally no problem in moving up to a higher speed-rated tire.

Most importantly: Put safety first. The speeds shown are test speeds; they are not recommended speeds.

Temperature Rating:

A comparative grade based on the tire’s resistance to heat and its ability to dissipate heat, again as measured under controlled conditions. The grades, from highest to lowest, are designated A – B – C. An A-rated tire is the coolest running, while a C-rating meets the minimum federal performance standards. These temperature grades are set based on a tire that is properly inflated and not overloaded.

Traction Grade:

A comparative grade based on the tire’s ability to stop on wet pavement, again as measured under controlled conditions on wet asphalt and concrete surfaces. The grades, from highest to lowest, are designated AA – A – B – C. A tire that is graded AA should have better traction or stopping performance than a tire with a lower grade, based on the specific straight-ahead braking tests.

Treadwear Grade:

A comparative grade based on the actual wear of the tire’s tread when tested under specific controlled conditions. All tires are tested under the same conditions to allow for comparison between manufacturers and between different lines of tires from the same manufacturer. The system is fairly easy to understand. A tire with a treadwear grade of 400 should have a useful tread life approximately twice as long as a tire with a treadwear grade of 200. The higher the grade, the better the expected treadwear.

Looking for new tires with optimal traction? Or are long-lasting treads a bigger priority? There’s a simple way to compare tire specs!

The Uniform Tire Quality Grading (UTQG) system was developed by the Department of Transportation (DOT) to assist consumers in the purchase of their tires by providing a standard grading system used by all tire manufacturers. Tire manufacturers use the UTQG system to grade their tires in three important areas: treadwear, traction and temperature. The UTQG grade for each tire is shown on the paper label affixed to the tire and is also molded in the sidewall.

Treadwear Grade – A comparative grade based on the actual wear of the tire’s tread when tested under specific controlled conditions. All tires are tested under the same conditions to allow for comparison between manufacturers and between different lines of tires from the same manufacturer. The system is fairly easy to understand. A tire with a treadwear grade of 400 should have a useful tread life approximately twice as long as a tire with a treadwear grade of 200. The higher the grade, the better the expected treadwear.

Traction Grade – A comparative grade based on the tire’s ability to stop on wet pavement, again as measured under controlled conditions on wet asphalt and concrete surfaces. The grades, from highest to lowest, are designated AA ABC. A tire that is graded AA should have better traction or stopping performance than a tire with a lower grade, based on the specific straight-ahead braking tests.

Temperature Grade – A comparative grade based on the tire’s resistance to heat and its ability to dissipate heat, again as measured under controlled conditions. The grades, from highest to lowest, are designated ABC. An A-rated tire is the coolest running, while a C-rating meets the minimum federal performance standards. These temperature grades are set based on a tire that is properly inflated and not overloaded.

UTQG is a great way to compare tires from various manufacturers and between specific lines from the same manufacturer. Remember: The UTQG isn’t a safety rating and it doesn’t guarantee a tire’s mileage performance - but you can use the UTQG in conjunction with price, warranty, appearance and recommendations to make the right tire choice for your needs. If you have any questions about UTQG or various tire lines, the Big O Tires team is always ready to help!

Hauling groceries – or bricks? The Load Rating or Load Index indicates how much weight each tire can safely support.

Every tire’s load rating is stamped into its sidewall. Once you know the load rating, you can use the chart below to determine the amount of weight that one tire can support. Then just multiply the weight by four - or the number of wheels on your vehicle - to determine your vehicle’s maximum load-carrying capacity.

Load Rating Table

Sometimes the maximum load (for example, 1060 kg) will be stamped into the sidewall so that you don't have to decipher the load rating. Remember: never install tires with a lower load-carrying capacity than the tires that were installed on your vehicle by the manufacturer!

Load Range:

The load rating is a measure of the tire's strength — its ability to hold air pressure under load.

The load rating influences the sidewall strength of a vehicle tire. If a tire has a load rating that is too low, the handling of the vehicle could become unstable as the sidewall buckles under the vehicle's weight. Conversely, a much higher load rating than needed can dramatically harshen ride quality.

The recommended load rating for a vehicle's tires can be found in its owner's manual. It is also normally affixed to a sticker located on one of the vehicle's door jams. If you are replacing tires supplied with the vehicle from the manufacturer, the load rating written on the tires is an appropriate guide.

Sidewall:

There are other codes on some tires that provide you with additional information, some of which are specific to light truck tire applications. Some of the other codes that you might find on your tires include:

LT = Stands for light truck application. Example: LT235/85R16
C, D or E = Load range indication for light truck applications
REIN = Reinforced
OWL = Outlined White Letters
RWL = Raised White Letters
ORWL = Outlined Raised White Letters
B, BLK, BW, BSW = Blackwall or Black Sidewall
W, WW, WSE – Whitewall or White Sidewall
XNW = Extra Narrow White Width
XL = Extra Load Capacity

Section Width:

The linear distance between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations).

Sidewall Aspect Ratio:

The ratio between tire height and width.

Important note on quoted prices:

Prices quoted do not include additional charges for sales taxes, mounting and balancing, valve stems, tire disposal fees, state recycling fees, tire protection plans and other charges. Prices may vary from one store to another or from one date to another. Tires listed may not be in stock at the identified store. Prices listed were received from individual stores and have not been verified by Big O Tires. Please call the Big O Store of your choice for up-to-date information and details on pricing, additional charges and product availability.

How Are Tire Sizes Specified?
The first number describes width of the tire (section), the second number describes the aspect ratio (profile), and the third number the wheel diameter (rim size).
Alignment makes a big difference in how long tires last, how much gas you use, and steering and safety. When you buy new tires, we'll make sure they're properly aligned with a free alignment check!

What is TPMS?


TPMS is an electronic system that monitors the air pressure in your tires and alerts you when they are under- or over-inflated. Proper tire inflation not only boosts your safety, but also the life of the tire and its fuel economy.

TPMS

Some components of the TPMS sensor may need to be replaced due to wear and corrosion over time. Our TPMS rebuild kit includes all the necessary parts to service your TPMS sensor and keep this important safety feature functioning properly.

About TPMS

Protect Your Purchase!

Have you considered our Tire Protection Package?

Available with purchase of new, non-Big O brand tires, TPP includes the following comprehensive coverage:


  • 3-Year Full Free Repair or Replacement Road Hazard

  • 3-Year Full Free Replacement Workmanship & Materials

  • 3-Year Free 24/7 Flat Tire Change

  • Limited Lifetime Prorated Repair
    or Replacement Coverage

  • Free Rotations and Rebalance for the Useful Life of Tire

  • Limited Mileage Warranty

Tire Protection ... On Us!


Your Big O brand tire purchase includes our Tire Protection Package, free of charge. Protection includes complimentary rotations and rebalances for the life of the tire, as well as 24-hour Roadside Assistance, available nationwide. Plus, we'll repair, replace or refund your tire in the event that it is damaged, free of charge for 3 years (pro-rated after).

TPMS

Drive away with confidence and peace of mind. We've got you covered. See Tire Warranty terms for details.

Protect Your Investment!


Available with the purchase of qualifying new tires, our Tire Protection Package provides comprehensive coverage you can count on. It includes complimentary rotations and rebalances for the life of the tire, as well as 24-hour Roadside Assistance, available nationwide. Plus, we'll repair, replace or refund your tire in the event that it is damaged, free of charge for 3 years (pro-rated after).

TPMS

Add TPP to your purchase today, and drive away with confidence and peace of mind. We've got you covered. See Tire Warranty terms for details.