Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
SAE J108-2013: Motorcycle Brake System Road Test Code – A Practical Overview
This SAE Recommended Practice establishes a uniform procedure for level road testing of brake systems for all classes of motorcycles intended for highway use. The standard covers instrumentation, test conditions, and procedures for evaluating brake effectiveness, fade, and recovery.
Essential Instrumentation and Test Conditions
| Instrument | Purpose |
|---|---|
| Pressure gauges | Measure lever and pedal force |
| Decelerometer | Measure deceleration |
| Thermocouple with indicator | Monitor brake temperature |
| Calibrated speedometer/odometer | Measure speed and distance |
| Ambient thermometer | Record ambient temperature |
| Optional: stopmeter, stopwatch | Measure stopping distance or time |
⚠️ Thermocouple Placement: Install thermocouples in the center of the most heavily loaded shoe. Use plug type, web-rim junction, or lining-edge insertion for accurate temperature measurement.
Test conditions require a level dry surface (±1% grade), ambient temperature 40-90°F for fade/recovery, and appropriate test speed. Vehicle test weight is calculated per formulas: W = C + 150S + P for three-wheelers or W = C + 200 lb for two-wheelers in effectiveness test.
Brake Proportioning and Test Procedures
To achieve balanced braking, two independent stops with front-only and rear-only are conducted at 50 mph. Deceleration versus pedal/hand lever force is plotted to find the input that yields a 60/40 front/rear retardation split. This proportioning is used for subsequent tests.
The test sequence includes preburnish check, first effectiveness test, burnish (200 stops at 30 mph), second effectiveness test, fade and recovery test. Initial brake temperature must be controlled (e.g., 150°F ±10°F for burnish).
🔍 Engineering Insight: Brake fade and recovery tests are critical. Thermal limits of the friction material and drum/rotor significantly affect stopping power. Consistent temperature before each stop ensures repeatable results.
During fade tests, after a baseline check, repeated stops at 50 mph with fixed input are performed, noting temperature rise and deceleration changes. Recovery tests follow after a cool-down period.
Frequently Asked Questions
- What is the scope of SAE J108-2013?
It covers level road test procedures for brake systems of highway motorcycles, including instrumentation, installation, and test methods for effectiveness, fade, and recovery. - How is vehicle test weight defined?
For two-wheeled motorcycles, test weight W = C + 150S + P (or W = C + 200 lb for effectiveness) where C is curb weight, S is seating capacity, P is payload for three-wheelers. - Why is 60/40 front-to-rear brake proportioning used?
This ratio provides balanced deceleration and stability. It is established by plotting deceleration vs input for each brake individually. - What ambient temperature is required for fade and recovery tests?
Ambient air temperature must be between 40°F and 90°F to ensure test validity and minimize environmental influence on brake behavior.
