The rear brake release time may be greater than the time specified in FMVSS 121, "air brake system". in addition, some tractors may have warped parking brake apply springs which also effect the rear brake release time. Consequence of defect: Tractors fail to meet the stopping distance specified in FMVSS 121 which is required to stop the truck safely.
Install a quick release valve in the trailer service air line and increase the diameter of the rear service brake line. Also inspect rear spring brake chamber and release if necessary.
