Did you REALLY check your Air Brakes before you Headed Out!

It is MORE than Measuring Stroke • Measure air brake chamber pushrod stroke • Measure for 90 degree applied brake angle • Measure brake lining thickness at the inspection hole

Measuring Brake Stroke: • Chock the wheels. • Build air system to about 120 PSI, turn the engine off. Release the parking brakes. • Using the chalk, mark each pushrod where it exits the brake chamber.

By making a few brake applications, reduce air system pressure to between 90-100 PSI. Now have a helper make and hold a FULL brake application, (or if working alone, use a Brake Mate shown elsewhere in this catalog). With the full application being maintained, go back under and measure the distance each chalk mark has moved. Measuring Brake Lining Thickness • Use the tip of the pre-measured by placing it beside the edge of the brake lining at the inspection hole. • Brake lining that is thicker than the gauge does not need to be replaced.

• Brake lining thinner than the gauge MUST BE replaced

• Measuring Excessive Stroke • An applied brake at 90 degrees is NOT the law, just a recommendation. To check the applied brakes simply

hold the 90 degree gauge along the pushrod at the slack adjuster where a right angle should be present.

Methods one or two • It is important to note that the body design and suspension of some vehicles may limit safe access to certain brake

components unless the vehicle is supported on a hoist or is over a pit or ramp. Also, some brake systems have covers or housings that conceal the brake linkage, making it impossible to inspect brake adjustment using the techniques described here.

• Secure the vehicle with wheel chocks or blocks. • Ensure air pressure is above 621 kPa (90 psi) and release the spring brakes. • Select one of the following methods:

– Method 1: Mark the pushrod at the brake chamber or at a suitable fixed reference point. (Use chalk, soapstone, marker or other similar instrument — marks must be narrow and precise.)

– Method 2: Measure the released position of the pushrod. (Measure and note the distance from a point on the pushrod to a suitable fixed point at the brake chamber. This is measurement number 1.)

• Raise or lower the air pressure by running the engine or pumping the brake pedal until both the primary and secondary air-tank gauges display 621 to 690 kPa (90 to 100 psi).

• Shut off the engine. • Press and hold the brake pedal in the fully applied position.• Determine the applied pushrod stroke. (Continue to use the previously selected method).

– Method 1: Measure the distance from the brake chamber or fixed reference point to the mark on the pushrod.– Method 2: Measure the applied position of the pushrod. (Re-measure and note the distance from the previously selected point on

the pushrod to the previously selected fixed point at the brake chamber. This is measurement number 2.) Subtract measurement 1 from measurement 2 to calculate the applied pushrod stroke measurement.

• Determine the number size (such as 16, 20, 24 or 30) and type (such as standard or long-stroke) of the brake chamber. • Determine the adjustment limit for the brake chamber. Compare the applied pushrod stroke to the applicable adjustment

limit and identify any brake that exceeds the adjustment limit as defective.

Methods one or two

Brake AdjustmentChart