When it comes to making brake rotors, there’s a lot that goes into testing them to ensure the internal structure, metallurgy and performance of the rotor is in good working order. One aftermarket rotor testing procedure can help ensure that the brake rotor is in tip-top shape.

That procedure is titled the J2928 Brake Rotor Thermal Cracking Procedure for Vehicles below 4,540 kg GVWR. Wow, what a name! The Society of Automotive Engineers (SAE) has approved this test to measure brake rotor thermal cracking under specific conditions.

This document merged together current industry tests and best practices, and the goal was to create a standardized test that could evaluate the aftermarket rotor’s ability to resist cracking using a dynamometer since rotors have to be able to withstand thousands of heat cycles without cracking or structural failure.

The procedures of the test, called the SAE J2928 for short, subjects a rotor to 150 heat cycles. A heat cycle is when a rotor is cold and then brought to a high temperature. During the heat cycle, a rotor will expand and contract, which can create fatigue in a rotor that can cause cracking and structural failure.

The rotor is inspected during the 150 heat cycles, which includes a dimension check and an inspection for damage. The goal of the test is to thermally and mechanically stress the rotor so any issues with the metallurgy or structure are exposed.

The J2928 also covers how to document and classify cracks, and unlike a USDA-grade or movie rating, this test is just a document and recommended procedures, and it is then up to the industry to adopt and embrace these tests.

Comparing and evaluating rotor manufacturers as well as adding consistency and accountability could benefit the supply chain and shops directly. It helps everyone in the supply chain speak the same language and sets criteria for measuring aftermarket motors.

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