Calculation of Load Limits - Tire Width vs. Tread Width
| Entry Date | March 7, 2008 |
|---|---|
| Issue Number | 08-018-SWC |
| Name | David Nguyen |
| Agency | American Trucking Associations, Inc. |
| Address | 950 N. Glebe Road Suite 210Arlington, VA, 22203United StatesMap It (opens in a new tab) |
| Phone | (703) 838-1970 |
| Fax | (703) 838-1786 |
| [email protected] | |
| Committee | Size and Weight Committee |
| Status | Closed |
| Summary of Issue | Tire width is not the same as tread width. Industry believes that 49 CFR 658.17 (f), which says "States may not limit tire loads to less than 500 pounds per inch of tire or tread width." is vague and results in differing interpretations by enforcement personnel. It can be misinterpreted that tire width is the same as tire tread in contact with the ground. |
| Justification or Need | In jurisdictions where load per inch width of tire restrictions are enforced, the difference in interpretation can produce widely varying figures that can put a vehicle out-of-service when, in fact, it is in compliance with the load limit using accepted industry practice. |
| Request for Action | A bulletin should be issued to field personnel clarifying that tire width should be obtained by reading the sidewall designation for nominal tire width. Tire width should not be measured as the part that is in contact with the ground. If the tire sidewall is not legible, the tire should be measured from sidewall to sidewall per TMC Recommended Practice 223B. This method is the industry norm for indicating tire width, as published by TMC, Society of Automotive Engineers (SAE), Tire and Rim Association, and followed by truck tire manufacturers. |