Product Code:SAE J2803
Title:Dimensional Compatibility for Commercial Vehicle Wheels to Air Disc Brake Calipers
Issuing Committee:Truck And Bus Wheel Committee
Scope: 1This SAE Recommended Practice defines the clearance line for establishing dimensional compatibility between air disc brake calipers and 22.5 inch diameter disc wheels and includes valve stem consideration. The clearance line establishes the maximum envelope for the caliper and minimum envelope for wheel and valve stems to allow interchangeability.This document addresses dimensional characteristics only and makes no reference to the performance, operational dynamic deflections or heat disipation of the system. It is up to the system integrator to ensure sufficient clearance exists betweent the caliper, wheel and valve stem to provide safe operating conditions. This document is required because the air disc brakes currently in the marketplace, and those of the forseeable future, can not provide accpetable brake performance while complying to the clearance lines defined in SAE J1865 or other packaging requirements. Additionally, J1865 does not take into account the swept area of the valve stem. This is not a concern for drum brake applications where the drum rotates with the wheel and valve stem. However, disc brake applications have the potential for contact between the valve stem and the brake caliper which can result in rapid depressurization of the tire.
Rationale: 1This SAE Recommended Practice defines the clearance line for establishing dimensional compatibility between air disc brake calipers and 22.5 inch diameter disc wheels and includes valve stem consideration. The clearance line establishes the maximum envelope for the caliper and minimum envelope for wheel and valve stems to allow interchangeability.This document addresses dimensional characteristics only and makes no reference to the performance, operational dynamic deflections or heat disipation of the system. It is up to the system integrator to ensure sufficient clearance exists betweent the caliper, wheel and valve stem to provide safe operating conditions. This document is required because the air disc brakes currently in the marketplace, and those of the forseeable future, can not provide accpetable brake performance while complying to the clearance lines defined in SAE J1865 or other packaging requirements. Additionally, J1865 does not take into account the swept area of the valve stem. This is not a concern for drum brake applications where the drum rotates with the wheel and valve stem. However, disc brake applications have the potential for contact between the valve stem and the brake caliper which can result in rapid depressurization of the tire.