Brake violations remain a common resource of roadside citations and even crashes and also it's necessary to ensure your fleets brakes space up to par.

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Photo : Jim Park

Nearly 1,600 vehicles were placed out of business for brake violations throughout the Commercial vehicle Safety Alliance’s unannounced Brake security Day in April.

On April 25, 52 U.S. And Canadian jurisdictions performed 11,531 roadside inspections ~ above commercial motor vehicles, and also 13.8% that the inspections ended in one out-of-service violation, around the very same as fora Brake safety and security Day event held in September of last year.

Just main later, legislation enforcement officials and brake safety specialists were top top hand in ~ the CVSA Brake safety Conference in Schaumburg, Illinois, offering in-depth information on what officers look for during brake inspections, plus advice to help drivers make certain their auto is all set to happen muster if the is selected because that inspection.

Based on the meeting, below are some refresher tips on inspecting her truck’s wait brakes.

Getting started

Always examine brake adjustments once brakes room cold. Stroke measurements will be longer when brakes are hot as result of heat growth of the brake drum.

Your first inspection plot is to identify the chambers and confirm their size based on the square-inch area of the chamber diaphragm.

Brake chamber size can be figured out by locating size markings engraved top top both the clamp and body that the chamber. If those markings space illegible, friend can also use a specially design caliper to get the correct dimension measurement that the chamber.

Commercial car brake chambers range in size from 6 to 36 through 30 the most common size in use. Command axle brakes are normally smaller, varying in sizes from 12 come 20. Together a ascendancy of thumb, larger size chambers are typically used on more heavier axles.

Once you’ve got the chamber size locked in, you need to determine if you’re taking care of standard or long-stroke chambers. This is important because the adjustment border for a long-stroke chamber can be as lot as ½ customs (13 mm) longer than the stroke size on a standard chamber.

Long-stroke chambers have the right to be established visually in three ways:

● The airlines connect to a square-shaped port on the brake chamber body. Traditional brake chambers have round airline ports.

● A trapezoidal-shaped tag put under the clamp bolt that suggests the brake chamber’s preferably stroke dimension (but no the brake convey limit).

● Markings on the brake chamber human body that suggest it is a long-stroke chamber and also only long-stroke diaphragms are to be used with the component.

Once you know for details the size and also stroke size of your brake chambers, it’s time to obtain down come the nitty-gritty of making certain your brakes space in compliance.


Source: CVSA

Measure used pushrod stroke

Now, you must decide on the method to identify the brake’s applied pushrod stroke:

● technique 1: mark the pushrod at one of two people the brake chamber or another fixed reference point using chalk, soapstone or a mite pen. The marks must be narrow and precise.

● technique 2: measure the released place of the pushrod and also note the distance from a point on the pushrod body to a fixed allude near the brake chamber.

Regardless of which method you chose, the resulting number is measurement 1. Now, one of two people raise or reduced the truck’s air push by either running the engine or pump the brake pedal till you have actually 90 come 100 psi suggested in both the main and secondary air tanks. Once you’ve gained the correct air press indicated, apply and also hold full pressure to the company brake pedal.

Next, you require to recognize the used pushrod stroke follow to the technique you selected to acquire that measurement. If girlfriend used method 1, measure the distance from the mark you do on the pushrod to one of two people the brake chamber or the fixed referral point. If girlfriend used an approach 2, measure up the used position that the pushrod. In both cases, her objective is to measure the distance from the formerly selected suggest on the pushrod come the formerly selected fixed suggest near the brake room to attain Measurement 2.

Now, based on your previously determined size and type of brake chamber, inspect Measurement 2 against the correct adjustment limit for the brake chamber. If the used pushrod stroke is longer than the adjustment limit, the brake is out of adjustment.


If you require a basic idea regarding whether your brakes are changed correctly and don’t have time to bring out a full-formed inspection, you can measure the free-stroke that a brake.

Photo: Jim Park

Taking brake cost-free stroke measurements

If you require a general idea as to whether or not your brakes are changed correctly and don’t have time to carry out a full-formed inspection, you have the right to measure the free-stroke that a brake, i beg your pardon gets much longer as the brake gets more and an ext out that adjustment.

In this approach, effectively chock and secure the vehicle, then rise underneath it and also using her hand or a an ideal pry bar, pull earlier on the pushbar far from the brake chamber and also measure exactly how much play is existing in the pushbar’s variety of motion. If the measure free-stroke distance exceeds ¾ customs (19mm), over there is a high likelihood the brake is the end of adjustment. In this instance, CVSA dictates checking the used stroke of the brake the right means to check correct adjustment.

Again, the CVSA guidelines stress that this an approach only gives restricted insight right into brake adjustment and is no a guarantee that the brakes space within embraced CVSA mediate limits.

Inspecting pushrod markings

To help simplify the brake inspection process, many brake manufacturers today note pushrods v indicator markings the can conveniently tell friend if a brake is in, or out, that adjustment.

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To check brakes making use of this method, check to make sure the auto is properly secured and chocked, then rise underneath and also inspect every brake pushrod. A manufacturer’s out-of-adjustment indicator will typically be a brightly fancy band around the pushbar. If the brake is within adjustment, this marking will be inside the body of the brake chamber and also not visible. However, if any part of the indicator marking is visible, either flush v the brake chamber confront or previous it, the brake is the end of adjustment.