In my 34-plus years as a technician, educator, and advocate for the tire industry, I have developed a natural skepticism towards government regulations. While the exact issues in question are too numerous to list, there have been a few instances where I not only agree with the regulation, but actually applaud the agencies inside the Beltway for making reasonable decisions. On Friday, July 22, the Federal Motor Carrier Safety Administration (FMCSA) registered a big win for the industry by answering an age-old question regarding tread depth measurements.
According to Section 393.75, the minimum tread depth for a truck tire is 4/32 of an inch on steer tires and 2/32 of an inch for tires in all other positions. If the tread depth in any major groove is below those limits, the driver will be in violation. While this seems simple and straightforward, it is far from either because up until recently, there was no definition of a “major tread groove.”
Asking enforcement officials to interpret a regulation will create a wide range of opinions regarding an issue like tread depth measurements. In the past, some might think the decoupling grooves on the outer shoulders of a highway tire in both steer and trailer tread designs are major tread grooves and issue a citation when one measurement in those areas is under the limit. Others could take the measurement between tread blocks on a drive tire.
Federal agencies get flooded with requests from industry groups like the Commercial Vehicle Safety Alliance (CVSA) and the American Trucking Assns. (ATA) each year. In this instance, both CVSA and ATA were cited in the Federal Register announcement as submitting “several petitions for rulemaking” and as a result of those and other efforts, the Final Rule defines a major tread groove as:
The space between two adjacent tread ribs or lugs on a tire that contains a tread wear indicator or wear bar. (In most cases, the locations of tread wear indicators are designated on the upper sidewall/shoulder of the tire on original tread tires.)
FMCSA also proposed adding an illustration to 393.75 to indicate the location of the tread wear bars or tread wear indicators to help identify where the major tread grooves are found. This makes it crystal clear to drivers, maintenance personnel, and enforcement officials where the tread depth measurements should be taken. Tire manufacturers mold symbols on the edge of the tread to show where the tread wear indicators are located. The wear bars aligned with those symbols are only located in major tread grooves, so the problem is solved. If the groove or space does not contain a tread wear indicator, then it cannot be used to determine if the minimum tread depth requirements outlined by 393.75 are being met. Discussion over.
The Final Rule also includes revisions to rear license plate lamp requirements and amends regulations regarding the operation of a vehicle with speed-restricted tires among other industry issues. A complete copy of the Final Rule can be found at https://www.gpo.gov/fdsys/pkg/FR-2016-07-22/html/2016-17364.htm
From what I can tell, this Final Rule covers a wide range of inspection, repair and maintenance regulations, and answers a lot of important questions. By defining a major tread groove, FMCSA ends an age-old debate on tread depth measurements. It was much needed and even more appreciated because it had become a matter of opinion, which is never consistent.
Next month, I’ll dissect the new language in 393.75 related to speed-restricted tires so everyone understands the requirements moving forward, and we can put that issue to bed as well.
