Dimension Compatibility for Commercial Vehicle Wheels to Air Disc Brake Calipers—Truck and Bus
This SAE Recommended Practice defines the boundary line for establishing dimensional compatibility between air disc brake calipers and 22.5”x8.25” disc wheels, including bent valve stems on steel wheels and manufacturer recommended valve stems on aluminum wheels. The line establishes the minimum wheel with valve stem envelope to allow interchangeability. The line does not accommodate customer-specific wheels (such as OEM-specific stylized wheels) or customer-specific brakes.
This document addresses dimensional characteristics only and makes no reference to the performance, operational dynamic deflections or heat dissipation of the system. It is up to the system integrator to ensure sufficient clearance exists between the caliper, wheel and valve stem to provide safe operating conditions. Mounting systems as noted are referenced in SAE J694.
Rationale: The purpose of this document is to define a boundary line for current air disc brake calipers on 22.5”x8.25” wheels, similar to the clearance lines for drum brakes provided in SAE J1865. One notable difference between this specification and the SAE J1865 drum brake specification is that the clearance lines in SAE J1865 do not account for the swept area of the valve stem.