[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2002] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR393.207] [Page 1125] TITLE 49--TRANSPORTATION CHAPTER III--FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 393--PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION--Table of Contents Subpart J--Frames, Cab and Body Components, Wheels, Steering, and Suspension Systems Sec. 393.207 Suspension systems. ( Sections 'a' through 'e' not shown ) (f) Air suspensions. The air pressure regulator valve shall not allow air into the suspension system until at least 55 psi is in the braking system. The vehicle shall be level (not tilting to the left or right). Air leakage shall not be greater than 3 psi in a 5-minute time period when the vehicle's air pressure gauge shows normal operating pressure.