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BC Air Brake Cheat Sheet

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Compressor, Governor & Reservoirs

  • Not published of exam
  • Compressor Build-Up Governor Cut-In/Out Safety Valve Wet Tank Check Valves

Dual Circuits & Warnings

  • Not published of exam
  • Primary vs Secondary Gauges Low-Air Warning Reduced Braking

Spring & Parking Brakes

  • Not published of exam
  • Drag Pressure Full Apply Range Caging Safety Breakaway Protection

Foundation Brakes & Adjustment

  • Not published of exam
  • Free Stroke Applied Stroke Slack Adjusters Type 30 Chamber

Stopping Distance & Driving

  • Not published of exam
  • Perception + Reaction Brake Lag Downgrade Control ABS Behavior

Pre-Trip & Endorsement Rules

  • Not published of exam
  • Leakage Limits Governor Check Test Format Retest Rules

Quick Facts

  • Exam BC Air Brake Knowledge Test
  • Format 25 MCQ
  • Pass Score 20/25 (80%)
  • Time Limit 45 minutes
  • Fee $15 per attempt
  • Endorsement Code 15
  • Retest Wait 7 days
  • Result Validity 1 year
  • After 3 Fails Repeat 7-hr course

Key PSI Checkpoints AI

  • 60 warns, 85 cuts in, 150 pops off
  • 60 psi warning 85 psi cut-in 150 psi safety valve 125 psi max

Wet Tank vs Service Reservoirs AI

Wet Tank (Supply)

  • Collects water, oil, carbon
  • First reservoir after compressor

Service Reservoirs

  • Feed primary and secondary circuits
  • Protected by check valves
  • Wet tank collects moisture first

Compressor & Build-Up AI

  • 50 to 90 psi Build-up pressure range tested
  • 3 minutes Max time to build
  • 1000-1200 rpm Fast idle engine speed
  • Compressor Supplies compressed air continuously
  • Air-over-hydraulic Also needs Code 15
  • Compressed air Higher force than hydraulic

Governor & Safety Valve AI

  • Governor Controls cut-in and cut-out
  • Cut-out 125 psi, stops compressor
  • Cut-in Before 80-85 psi, restarts
  • 105-135 psi Typical max range
  • 20 psi spread Cut-out minus cut-in
  • 150 psi Safety (pop-off) valve vents

Reservoirs & Check Valves AI

  • Wet tank First reservoir, supply tank
  • Wet tank job Traps water, oil, carbon
  • Primary reservoir Feeds drive axle brakes
  • Secondary reservoir Feeds steering axle brakes
  • One-way check valve Blocks backward air loss

Primary vs Secondary Circuit DU

Primary Circuit

  • Controls drive axle brakes
  • Nearest section to pedal

Secondary Circuit

  • Controls steering axle brakes
  • Backs up primary failure
  • Primary controls drive axle brakes

Low-Air Warning Response DU

  • Warning activates while driving → Confirms pressure below 60 psi
  • Pressure below 60 psi → Stop as soon as safely possible
  • Pressure keeps falling further → Spring brakes may begin drag
  • Pressure reaches 20-45 psi → Spring brakes fully apply
  • One circuit fails only → Other circuit still stops truck
  • Reservoir shows 80 psi → Max applied pressure is 80

Dual Circuit Basics DU

  • Primary circuit Drive (rear) axle brakes
  • Secondary circuit Steering (front) axle brakes
  • Dual foot valve Primary section nearest pedal
  • One circuit fails Other circuit still brakes
  • Reduced braking Stop immediately, get service

Gauges & Low-Air Warning DU

  • Low-air warning Activates below 60 psi
  • 60 psi = 414 kPa threshold
  • Applied pressure cap Never exceeds reservoir pressure
  • 80 psi tank example Max 80 psi applied
  • Dual gauges Show primary and secondary
  • Warning stays on Stop safely, do not drive

Spring Brakes vs Service Brakes SP

Spring (Parking) Brakes

  • Mechanical spring force applies
  • Auto-apply at 20 to 45

Service (Foot Valve) Brakes

  • Air pressure applies force
  • Tested at 90 to 100
  • Spring brakes park; service brakes stop

Spring Brake Safety Check SP

  • Vehicle must be moved → Cage spring brake chambers
  • Before caging any chamber → Block the wheels first
  • Parking on a grade → Set parking brake, chock wheels
  • Air supply line ruptures → Spring brakes auto-apply instantly
  • Relay brakes, no springs → Chock wheels when parked
  • Confirming parking brake holds → Gently tug in low gear

Spring Brake Pressures SP

  • Drag begins Below about 60 psi
  • Full auto-apply About 20 to 45 psi
  • Spring brakes Mechanical spring force, not air
  • Mounted Rear axles only, typically
  • Compounding Never combine spring and service
  • Breakaway Supply rupture auto-applies springs

Parking & Breakaway Rules SP

  • Caging Block wheels first, always
  • Tractor protection valve Isolates trailer air loss
  • Relay emergency, no springs Must chock wheels parked
  • Tug test Confirm parking brake holds
  • Never use Spring brakes as service brake

Stroke Check Order FO

  • Pry free stroke first, then apply and hold
  • 0.75 in free defect 1.75 in applied defect 2 in auto defect

Free Stroke vs Applied Stroke FO

Free Stroke (Pry)

  • Good range 0.5 to 0.75
  • Defect over 0.75 in

Applied Stroke (Full)

  • Good range 1 to 1.5
  • Defect over 1.75 in
  • Pry method versus full application

Foundation Brake Parts FO

  • Brake chamber Converts air to force
  • Pushrod Transfers chamber force outward
  • Slack adjuster Lever to s-cam
  • S-cam Rotates, spreads brake shoes
  • Drums/linings Friction surfaces that stop
  • Brake fade Overheated drums lose grip

Manual vs Automatic Slack Adjuster FO

Manual Slack Adjuster

  • Needs periodic manual adjustment
  • Applied defect over 1.75 in

Automatic Slack Adjuster

  • Self-adjusts during each stop
  • Applied defect over 2 in
  • Manual needs adjusting, auto self-adjusts

Stroke Limits FO

  • Free stroke good 0.5 to 0.75 in
  • Free stroke defect Over 0.75 in
  • Applied stroke good 1 to 1.5 in
  • Applied stroke defect Over 1.75 in
  • Type 30 auto defect Over 2 in stroke
  • Type 30 force About 3000 lb at 100 psi

Stopping Distance Order ST

  • Perceive, react, lag, then brake to stop
  • 0.75 sec perceive 0.75 sec react 0.4 sec brake lag

Stopping Distance Parts ST

  • Perception time About 0.75 second
  • Reaction time About 0.75 second
  • Brake lag About 0.4 second (air)
  • Total stopping distance Perception + reaction + lag + braking
  • Hydraulic brakes React almost instantly, no lag

Driving Technique Facts ST

  • Downgrades Use gear that climbed hill
  • Engine retarder Auxiliary slowing, saves brakes
  • ABS stop Apply firm, continuous pressure
  • ABS light stays on Anti-lock off, brakes work
  • Wet brakes Apply light pressure, dry them

Leakage Limit Ladder PR

  • Three, four, six: single, one-trailer, two-trailer
  • 3 psi single unit 4 psi one trailer 6 psi two trailers

Single Unit vs Combination Leakage PR

Single Unit (Class 3)

  • Max 3 psi per minute
  • No trailer air lines

Combination (1-2 Trailers)

  • Max 4 to 6 psi
  • More air line volume
  • More trailers allow more leakage

Pre-Trip Leakage Sequence PR

  • Engine off, brakes released → Watch gauge one full minute
  • Single unit, no trailer → Allow max 3 psi drop
  • One trailer attached → Allow max 4 psi drop
  • Two trailers attached → Allow max 6 psi drop
  • Testing applied leakage → Hold full application 90-100 psi
  • Any audible leak found → Fail vehicle, needs repair

Exam Facts PR

  • 25 questions Total test questions
  • 20 correct Passing threshold (80%)
  • 45 minutes Maximum time allowed
  • $15 Fee per attempt
  • Code 15 BC air brake endorsement
  • 1 year Knowledge test validity
  • 7 days Standard retest wait

Pre-Trip Leakage Limits PR

  • Single unit (Class 3) Max 3 psi per minute
  • One trailer combination Max 4 psi per minute
  • Two trailer combination Max 6 psi per minute
  • Test pressure Full application, 90-100 psi
  • Test duration One minute, engine off

Pre-Trip Check Steps PR

  • Cut-in check Pump to 80% max pressure
  • Cut-in confirms Rebuilds before 80 psi
  • Leak check Engine off, listen closely
  • Pre-trip required Before every day's first trip
  • Trip inspection report Written report for covered vehicles

Common Traps

Confusing Cut-In With Cut-Out

  • Cut-in restarts near 80 to 85 ≠ Cut-out stops near 125 psi

Mixing Up Free And Applied Stroke

  • Free stroke defect over 0.75 ≠ Applied stroke defect over 1.75

Ignoring The Low-Air Warning Light

  • Means pressure is below 60 ≠ Stop safely as soon as possible

Caging A Spring Brake Unsafely

  • Always block wheels first ≠ Truck can roll away

Assuming Applied Pressure Exceeds Reservoir

  • Applied pressure never exceeds reservoir ≠ 80 psi tank caps output

Treating Auto Slack As Maintenance-Free

  • Manual adjusting can hide problems ≠ Over 2 in needs repair

Shifting To A Higher Gear Downhill

  • Use the gear that climbed ≠ Never shift up on downgrades

Last Minute

  • 1. 25 questions, 20 correct required
  • 2. 45-minute time limit total
  • 3. Low-air warning means below 60psi
  • 4. Governor cuts in near 85psi
  • 5. Safety valve vents near 150psi
  • 6. Free stroke over 0.75in needs adjustment
  • 7. Applied stroke over 1.75in needs adjustment
  • 8. Single unit leakage limit 3psi
  • 9. Combination leakage limit 4 to 6psi
  • 10. Block wheels before caging springs

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