Top 10 Questions About Tires - Wheel Works

What is meant by speed rating?

The speed rating of a tire indicates the speed category (or range of speeds) at which the tire can carry a load under specified service conditions. The speed rating system used today was developed in Europe in response to the need to control the safe performance of tires at standardized speeds. A letter from A to Z symbolizes a tire's certified speed rating, ranging from 5 km/h (3mph) to above 300 km/h (186 mph). This rating system, listed below, describes the top speed for which a tire is certified. It does not indicate the total performance capability of a tire.

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When this speed rating system was originally developed, the Unlimited V category of over 210 km/h (130 mph) was the top speed rating a tire could achieve.

SPEED RATING Speed Symbol Speed (km/h) Speed (mph) A1 5 3 A2 10 6 A3 15 9 A4 20 12 A5 25 16 A6 30 19 A8 40 25 B 50 31 C 60 37 D 65 40 E 70 43 F 80 50 G 90 56 J 100 62 K 110 68 L 120 75 M 130 81 N 140 87 P 150 94 Q 160 100 R 170 106 S 180 112 T 190 118 U 200 124 H 210 130 V 240 149 W 270 168 Y 300 186

As manufacturers made more tires that did not fit this category, it was necessary to better regulate performance at standardized speeds to ensure safety. The Limited V category of 250 km/h (149 mph) was then created, and the Z speed rating was added as the top speed rating that a tire could achieve. W and Y limited speed symbols have been added as higher speed categories.

Always consult the manufacturer for the maximum speed of Unlimited Z tires. Speed rating is identified as a part of the tire's sizing or service description.

In the latest attempt to standardize tire designations, all ratings except Unlimited ZR incorporate the speed symbol and load index as the tire's service description. For example:

205/60R15 91V 205 = Section Width in Millimeters 60 = Aspect Ratio R = Radial Construction 15 = Rim Diameter in Inches 91 = Load Index (Service
Description) V = Speed Symbol

When "ZR" appears in the size designation with the service description, the maximum speed is as indicated by the service description:

EXAMPLES Tire Designation Maximum Speed P275/40ZR17 93W 270 km/h (168 mph) P275/40ZR17 93Y 300 km/h (186 mph)

For tires having a maximum speed capability above 240 km/h (149 mph), a "ZR" may appear in the size designation. For tires having a maximum speed capability above 300 km/h (186 mph), a "ZR" must appear in the size designation. Consult the tire manufacturer for maximum speed when there is no service description.

What does UTQG mean?

Uniform Tire Quality Grading

UTQG is intended to provide simple, comparative data for your use in making an informed buying decision. However, the ratings are based upon test results achieved under very specific conditions. As a result, misinterpreting the comparative data as it relates specifically to your particular driving habits, conditions, etc., is a possibility. UTQG designates the comparative performance levels of a tire based upon government-specified tests. Tire manufacturers and brand name owners are required to grade regular and all-season tires in three categories: Treadwear, Traction, and Temperature.

Dot Quality Grades

All passenger car tires must conform to Federal Safety Requirements in addition to these grades.

Treadwear

The treadwear grade is a comparative grade assigned by the manufacturer based on the wear rate of a tire when tested under controlled conditions on a course that meets government-specified requirements. For example, a tire graded 150 would wear one and a half (1 1/2) times as well as a tire graded 100 under the controlled test conditions. The relative performance of tires depends upon the actual conditions of their use and may depart significantly from the norm due to variations in driving habits, service practices and differences in road characteristics.

Traction AA, A, B, C

The traction grade is based on wet skid tests of a tire on government-specified concrete and asphalt surfaces. The traction grade is based on a straight-ahead wet braking traction test and does not include a cornering traction test. The comparative tire grade letters, AA, A, B, and C (AA being the highest and C being the lowest) represent the tire's ability to stop the vehicle on wet pavement under the controlled test conditions. Ice and snow traction capabilities are not tested.

Warning:

The temperature grade is established for a tire that is properly inflated and not overloaded. Excessive speed, under inflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure.

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Example #1:

A tire with the ratings of TREADWEAR 80, TRACTION B, TEMPERATURE C, is interpreted by the manufacturer as having:

• TREADWEAR grade less than that of a tire graded 100.
• TRACTION capability greater than tires of C grade, but not as good as tires of AA or A grade.
• TEMPERATURE performance on the laboratory high-speed test greater than required by the government standards, but less than tires graded B or A.

Example #2:

A tire with same brand name and same construction type with ratings of TREADWEAR 160, TRACTION A, TEMPERATURE B, compares to the tire in example #1 as follows:

• TREADWEAR is graded two times better than the tire in example #1.
• Wet TRACTION and TEMPERATURE are better than the tire in example #1.

Important Note

Keep in mind that comparing the performance of various tires is too complex to be based exclusively on UTQG grades.

• UTQG grades are not government grades. They are manufacturer grades that are not based on head-to-head interbrand testing. Test data is not typically submitted to the National Highway Traffic Safety Administration.
• Treadwear grades are not a guarantee for a given mileage warranty, or an indicator of overall tire quality. Treadwear grades are assigned by the manufacturer for comparison purposes within the same brand names and construction types only.
• UTQG grades are not safety ratings. Overall tire quality and safety are not graded. Tire selection based on any one, two, or even three UTQG ratings may not satisfy your needs.
• One brand name of tires cannot be considered superior or inferior to another brand name of tires based solely on UTQG grades.
• UTQG grades are not required for snow tires, light truck tires and maximum traction tires.
• UTQG is used but not required in Canada.

What is the repairable area of a tire?

Non-RFT (Non Run Flat Tires)

We only repair tires in accordance with the RMA (Rubber Manufacturers Association) recommended procedures. Some punctures cannot be seen with the naked eye and other measures are taken to find such punctures (soapy water and tire water tubs).

RFT (Run Flat Tires)

No tire, regardless of its design or quality, is indestructible. RFT tires can be ultimately rendered unusable due to a puncture or other road hazard as well as from improper run-flat or low pressure operation. Some punctures may be repaired under certain circumstances, with restrictions and subject to prescribed procedures.

When driven flat or with low pressure, factors affecting reparability include vehicle speed, load, handling and maneuvering; the amount of inflation pressure lost; and ambient temperature. In any situation, the extent and location of direct damage from a puncturing object or other road hazard are also critical factors.

RFT tires are not repairable in any of the following situations:

• If the tire is described as, "Do Not Repair" on the sidewall.
• If the tire was operated with inflation pressure less than 15 psi (100 kPa).
• Abrasion or other damage is present on the exterior tread, sidewall or bead areas.
• Abrasion, wrinkling, or separation is present on the tire interior.
• Any condition or damage is present that disqualifies repair of a conventional tire.

Run-Flat Certified Retailers will fully inspect your tire, inside and out, to determine if the tire can be repaired. Tire damage is not always visible from the outside and the tire must be removed from the wheel for a complete inspection.

Note: Some vehicle manufacturers recommend not using repaired tires. Such recommendations apply to RFT tires. Use of RFT tires deemed non-repairable may result in damage to the vehicle, injury, or death. Consult your vehicle owner's manual or contact the vehicle manufacturer before operating a repaired tire on your vehicle.

WHAT IT DOES

This feature monitors your tires’ pressures and warns you if you have one or more under-inflated tires. Poorly inflated tires are prone to blow outs and may make it more difficult to brake or steer. Some versions of this feature can also detect over-inflation. Both under- and over-inflation will affect the life of your tires and your car’s gas mileage.

THE TECHNOLOGY BEHIND IT

There are two main types of TPMS sensors. Direct sensors are small, wireless devices inside each tire, which report the tire’s pressure reading to your dashboard. Indirect sensors work by measuring wheel spin and can only tell if a tire’s pressure is low.

WHAT YOU NEED TO DO

If your TPMS symbol is on, check the pressure for each tire to determine if one or more tires have abnormal pressure readings. Add or subtract air at a gas station to their recommended pressure ranges. In many cars, the TPMS symbol should then no longer activate. If it does, there may be a problem with the sensor itself as many use a watch battery that lasts about 5 to 10 years.

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