Reading Your Tire
Speed rating and Load-Carrying Capacity
Many tires come with a service description added onto the end of the tire's size. These service descriptions contain a two-digit number (load index) and a letter (speed rating). The load index is a representation of the maximum load each tire is designed to support. Because the maximum tire load-carrying capacity is branded on the tire's sidewall, the load index is used as a quick reference.
Use the following chart to determine the maximum load-carrying capacity based on a tire's load index:
Replacement Guidelines for Speed-Rated Tires
When replacing a tire designated with a speed rating, the new tire's speed rating should be equal or higher than the tire speed rating of the OE placard. This rule is to avoid conflicting tire speed capabilities and the possibility of misapplication, particularly because one tire may be constructed to perform under a higher speed than another. If tires with different speed ratings are mounted on the same vehicle, the lowest speed rated tire dictates the maximum vehicle speed.
Repair of Speed-Rated Tires
Because the tire manufacturer cannot monitor the quality of the repairs for speed-rated tires, once such a tire is repaired for any reason, that area ultimately diminishes the tire's designated speed rating. This applies to Yokohama tires with ratings of "N" or higher. Although the warranty will cover warrantable conditions unrelated to the repair area, the tire no longer is representative of its original manufactured condition because it has been altered. As a result, the speed rating of the tire is void after repairs have been performed. The tire is capable of running at normal sustained highway speeds up to 85 MPH if repairs are made following RMA Standards. Punctures and nail holes up to 1/4 inch diameter which are confined to the tread area may be patched permanently only from the inside of the tire along with filling the perforation of the tread caused by the nail. NEVER REPAIR TIRES WORN BELOW 2/32 INCH TREAD DEPTH. Some OE vehicle manufacturers do not allow repairs of any kind.
Repair of Run-Flat Tires
Advan Sport ZPS Run-Flat tires are not to be repaired following an injury. The tire will be replaced on a prorated basis under the terms of the limited warranty for AVS Sport Run-Flat tires. Never mix Run-Flat tires with tires that do not have Run-Flat technology. Never mix Run-Flat tires with different brands or technologies.
Speed ratings are certified maximum sustained speed designations assigned to passenger car radials and high performance tires. Because of the evolution of high-speed passenger car travel, it was necessary to establish a way to rate a tire's high-speed capability. In the U.S., these ratings are based on tire testing in laboratory conditions under simulated loads. For a tire to be speed rated, it must meet certain minimum industry standards for reaching and sustaining that specified speed. Domestically, high performance tires typically are speed rated. Yokohama defines high performance tires with a speed symbol of "H, Q, V, W, Y," or "Z". Speed symbols may currently be marked on a tire in any of three ways: 205/60ZR15; 205/60ZR15 89W; or 205/60R15 89W. The International Standard Organization (ISO) system currently serves as a worldwide standard for tire markings. At the end of a transition period, any speed symbol denoting a fixed maximum speed capability will be at the end of the service description following the tire marking (illustrated in the second and third examples above).
The Tire Industry Safety Council bulletin says:
"A reasonable person realizes that driving speeds are dictated by many factors, particularly such things as the weather, road surface and mechanical condition of the vehicle. These tire symbols do not mean that motorists can drive safely at the maximum speed for which the tire is rated or in excess of the posted speed limits."
If tires with different speed ratings are mounted on the same vehicle, the tire with the lowest rating will dictate safe maximum vehicle speed.
|Speed Symbol||(MPH)||(KPH)||Open Ended Speed Category|
|(Y)||Above 186||Above 300|
Speed ratings apply only to the tire, not to the vehicle. Putting a speed rated tire on any car does not mean the car can be operated at the tire's rated speed.
* This refers to tires that have a maximum speed capability above 240 KM/H (149 MPH). "Z" may appear in the size designation. Tires that have a maximum speed capability above 300 KM/H (186 MPH) must have a "Z" appear in the size designation. Consult the tire manufacturer for maximum speed when there is no Service Description.
Winter Tires and Speed Ratings
To maintain tire speed capacity indicated on the vehicle placard, winter tires with the same or higher speed rating should be used. If you decide to use winter tires with speed ratings below what is shown on the vehicle placard, the maximum vehicle operating speed must be reduced to the lowest tire speed rating of the tire mounted on the vehicle. In all cases, Yokohama recommends operating speeds not in excess of legal posted speed limits and that speed be reduced appropriately based on weather and road conditions. Winter tire speed ratings do not indicate safe vehicle operating speeds for winter road conditions, including snow, ice, water etc., and drivers must modify vehicular speeds based upon adverse climate changes and conditions.