What is the most reliable way to inspect brake adjustment?

Measure the applied pushrod stroke

Ontario Air Brake (Z): Brake adjustment and pushrod stroke

Daily stroke checks, identifying chamber size and long-stroke chambers, the two measuring methods at 90 to 100 psi, the adjustment limits chart and automatic slack adjusters.

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Brake adjustment and pushrod stroke · Question 1Score 0/0

Is the engine running or off while you hold the brakes applied to measure stroke?

Tip: press 1–4 to answer and Enter for the next question.

Study reference: MTO Air Brake Handbook (online edition, Feb. 2026), Ch. 11 Inspecting Air Brake Adjustment

All 24 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

Is the engine running or off while you hold the brakes applied to measure stroke?
1. Running at 1,200 rpm
2. Running at idle
3. Off
4. Running only for the trailer
What is the adjustment limit for a type 30 long-stroke chamber with square ports?
1. 3 in. (76 mm)
2. 2-1/2 in. (64 mm)
3. 2-1/4 in. (57 mm)
4. 2 in. (51 mm)
How often must pushrod stroke be inspected?
1. Every 5,000 km
2. At least weekly
3. At least daily
4. Only after a brake job
What is the most reliable way to inspect brake adjustment?
1. Listen for air when braking
2. Measure the applied pushrod stroke
3. Check the drum temperature
4. Feel how far the pedal travels
How much can adjustment limits differ between standard and long-stroke chambers?
1. By about 1 mm
2. By about 5 mm
3. By 19 mm or more
4. They never differ
Before measuring pushrod stroke, what must air pressure be?
1. At zero, all tanks drained
2. Below 60 psi, spring brakes applied
3. Above 90 psi, spring brakes released
4. Exactly 120 psi, engine running
What is the most visible and permanent sign of a long-stroke brake chamber?
1. Square air ports
2. A yellow clamp
3. Round air ports
4. A blue pushrod
Using Method 2, how do you get the applied stroke?
1. Divide the applied reading by two
2. Add the two readings together
3. Use only the released reading
4. Measurement 2 minus measurement 1
On a long-stroke chamber, what does the trapezoidal tag under the clamp bolt show?
1. The brake adjustment limit
2. The chamber's maximum stroke
3. The chamber's air pressure rating
4. The date of last adjustment
While measuring applied stroke, what should both tank gauges read when you hold the pedal down?
1. 60 to 70 psi
2. 140 to 150 psi
3. 110 to 130 psi
4. 90 to 100 psi
A driver holds an Ontario air brake adjustment certificate. Which brakes may they readjust?
1. Those with automatic slack adjusters only
2. Those with manual slack adjusters only
3. Any brake on any vehicle
4. Only trailer brakes
How else can you find a chamber's size if no records are available?
1. Check the colour of the air line
2. Clamp diameter or size markings
3. Read the markings on the tire sidewall
4. Count the folds in the diaphragm
In Method 1, how do you mark the pushrod?
1. A wide strip of coloured tape
2. A narrow, precise chalk line
3. A large paint dab on the drum
4. A deep scratch made with a file
What happens to pushrod stroke as brake linings wear?
1. It becomes zero
2. It stays the same
3. It decreases
4. It increases
An automatic slack adjuster keeps needing readjustment. What does that mean?
1. The driver should adjust it every day
2. It is working normally for its type
3. The drum simply needs more grease
4. It is defective; a technician must fix it
Is it legal to drive with one brake out of adjustment if the others are fine?
1. Yes, until the next annual
2. Yes, on the trailer only
3. No, it is prohibited
4. Yes, below 80 km/h
Your truck has automatic slack adjusters. Must you still inspect brake adjustment?
1. Only once a year
2. No, they never go out of adjustment
3. Yes, adjustment must still be checked
4. Only on the trailer
A standard (round-port) type 30 clamp chamber: past what applied stroke is the brake out of adjustment?
1. 2-1/2 in. (64 mm)
2. 1-3/4 in. (45 mm)
3. 2 in. (51 mm)
4. 1-3/8 in. (35 mm)
What is usually the easiest way to learn your vehicle's brake chamber sizes?
1. Count the bolts on the clamp ring
2. Measure the length of the pushrod
3. Your employer or the owner's manual
4. Weigh each chamber on a scale
Which demonstration is part of the MTO air brake practical test?
1. Changing the governor setting
2. Measuring applied pushrod stroke
3. Readjusting a slack adjuster
4. Replacing a brake chamber
The largest common chamber, a standard type 36, may not exceed which applied pushrod stroke?
1. 2-1/2 in. (64 mm)
2. 1-3/4 in. (45 mm)
3. 2 in. (51 mm)
4. 2-1/4 in. (57 mm)
Your steer axle uses standard type 24 chambers. Which stroke limit applies to them?
1. 1-3/4 in. (45 mm)
2. 2 in. (51 mm)
3. 1-3/8 in. (35 mm)
4. 2-1/4 in. (57 mm)
What is the most common brake chamber size?
1. Size 12
2. Size 36
3. Size 30
4. Size 20
What does a pushrod stroke indicator show?
1. The date of the last brake inspection
2. Stroke is past the limit
3. How much brake lining is left
4. The chamber's current air pressure

Brake adjustment and pushrod stroke: key rules to remember

Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗

Why and how often

As brakes wear, pushrod stroke increases; wear rates vary with the vehicle and conditions.
Pushrod stroke must be inspected at least daily; when it exceeds the adjustment limit the brake is out of adjustment.
Measuring the applied pushrod stroke is the most reliable way to check adjustment.

Identifying the chamber

Adjustment limits depend on chamber size and type, so you must identify the chamber.
Size can be found by measuring the clamp diameter (special tool) or reading the size marking, which may need cleaning first; the easiest source is the employer or the owner's manual.
Size 30 is the most common; sizes 16, 20, 24 and 36 are also used.
Long-stroke chambers have square air ports (standard chambers have round ports), a trapezoidal tag under the clamp bolt showing maximum stroke (not the adjustment limit), and markings saying to use only long-stroke diaphragms.
Square ports are the most visible and permanent sign of a long-stroke chamber.
Limits for standard and long-stroke chambers of the same size can differ by 19 mm or more.

Measuring applied stroke

Chock the wheels, make sure pressure is above 90 psi (621 kPa) and release the spring brakes.
Method 1: put a narrow, precise chalk or marker line on the pushrod at the chamber or a fixed reference point.
Method 2: measure the distance from a point on the pushrod to a fixed point at the chamber (measurement 1).
Bring both primary and secondary gauges to 90–100 psi (621–690 kPa), shut off the engine and hold the pedal fully applied.
Method 1: measure from the chamber or reference point to the mark. Method 2: measure again (measurement 2) and subtract measurement 1.
Identify the chamber size and type, look up its adjustment limit and mark any brake that exceeds it as defective.
Demonstrating an applied-stroke measurement is part of the MTO air brake practical test.

Clamp-type chambers

Type 30 standard: 2 in. (51 mm). Type 30 long-stroke with square ports: 2-1/2 in. (64 mm).
Types 16, 20 and 24 standard: 1-3/4 in. (45 mm); their long-stroke "L" versions: 2 in. (51 mm).
Type 24 long-stroke with square ports: 2-1/2 in. (64 mm).
Type 36 standard: 2-1/4 in. (57 mm). Type 30 DD3 (bus/coach): 2-1/4 in. (57 mm).
Type 12 and type 9: 1-3/8 in. (35 mm). Type 6: 1-1/4 in. (32 mm).

Indicators and slack adjusters

Many pushrods have an indicator that becomes visible when stroke passes the limit; indicators must be correctly installed and drivers trained to read them.
Automatic slack adjusters avoid routine manual readjustment, but adjustment must still be inspected.
An automatic slack adjuster that keeps needing readjustment is defective and must be repaired by a certified technician; never adjust it yourself.
Only certified technicians, or drivers holding an Ontario air brake adjustment certificate, may readjust manual slack adjusters; that certificate does not cover automatic adjusters.
Ontario law prohibits operating a vehicle with a brake out of adjustment.

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