A rule mandating a reduction in stopping distances for heavy-duty trucks is rumored to be coming in May. The rulemaking process started in 2002.
The anticipated revision of Federal Motor Vehicle Safety Standard 121 is expected to shorten stopping distances for heavy-duty trucks by 20 percent to 30 percent.
Today, most tractors stop in 255 to 292 feet. The 30 percent target cannot be met with 15-inch by 4-inch drums on steer axles. Meeting the cut to 248 feet for tractors would require 16½-inch by 7-inch front drums and 8”-inch wide rears.
If a 75 mph requirement is added, trucks will need front air disc brakes. LL