Issue link: http://read.dmtmag.com/i/34501
WEAR BARS MICHELIN ® truck tires contain “wear bars” in the tread grooves of the tire tread, which show up when only 2⁄32nds of an inch or less of tread remains. These tread depth indicators are identified on the shoulder by the Michelin Man. Tread depths should not be taken on the wear bar indicators. When the tread is worn level with the wear bar indicators (from either even or irregular wear), the tire must be removed from service. (Federal law requires truck tires on steer axles to have at least 4⁄32nds of an inch tread depth and all other axles have a 2⁄ 32nd inch limit.) presumably would be based upon either the tire manufacturer’s published technical data for overall width or the width as marked on the sidewall of the tire (which may require conversion from Metric to English units). It is recommended to contact your state’s DOT office to confirm the current Load Per Inch Width Law. For example, if a state allows for 550 pounds per inch width, a tire marked 11R22.5 could carry up to 6,050 pounds (11 x 550) or a total of 12,100 pounds on the steer axle (2 x 6,050). Another way to look at it is to take the total weight carried and divide by the stated Inch Width Law to determine the appropriate size tire. If a commercial front end loader (sanitation vehicle) wants to carry 20,000 pounds in a state with a 600 pound per inch width limit (20,000/600 = 33.3), you would need a tire that is at least 16.7 inches wide (33.3/2). In this case a 425/65R22.5 could legally carry the load (425/25.4 = 16.7 inches Metric to English conversion). The two formulas are: – Load Per Inch Width Law x tire section width x number of tires = gross axle weight limit – Gross axle weight / Inch Width Law / number of tires = minimum tire section width needed Do not exceed the gross axle weight ratings (GAWR) for any axle on the vehicle. Do not exceed the maximum pressure capacity of the wheel. Consult the wheel manufacturer in these cases. DRIVE AT PROPER SPEEDS The maximum continuous speed at which MICHELIN ® ® ® truck tires can be operated is indicated in the MICHELIN data books. See Section Nine, Appendix under Publications, Videos, and Websites (Page 139) for complete listings of the MICHELIN data books. This DO NOT OVERLOAD The maximum load that can be put on a truck tire is dependent upon the speed at which the tire will be used. Consult a MICHELIN ® Truck Tire dealer or the application data books for complete information on the allowable loads for application. Tires that are loaded beyond their maximum allowable loads for the particular application will build up excessive heat that may result in sudden tire destruction, property damage, and personal injury. Some states have enacted “Load Per Inch Width” regulations for the purpose of governing axle weight on (primarily) the steering axle of commercial vehicles. These regulations provide a carrying capacity of a certain number of pounds per each cross-sectional inch (unloaded) across the tire’s width. The determination of the tire’s width can vary from state to state but speed varies for each type of tire and depends on the type of application. Consult MICHELIN ® Consumer Care (1-888-622-2306) for assistance in determining the maximum speed for your application. Exceeding this maximum speed will cause the tire to build up excessive heat that can result in sudden tire destruction, property damage, and personal injury. In any case, legal speed limits and driving conditions should not be exceeded. High speed driving can be dangerous and may be damaging to your tires. When driving at highway speeds, correct inflation pressure is especially important. However, at these speeds, even with correct inflation pressures, a road hazard, for example, is more difficult to avoid. If contact is made, it has a greater chance of causing tire damage than at a lower speed. Moreover, driving at high speeds decreases the time available to avoid accidents and bring your vehicle to a safe stop. Section Three: Extending Tire Life 41