The Air Brakes section of the CDL exam has some of the most specific technical vocabulary in the entire test. Terms like "governor cut-out pressure," "pushrod stroke," and "dual air system" don't appear anywhere in everyday English — they're exclusive to commercial trucking. That's actually good news: it means you can study exactly what you need, and nothing else.
| English Term | Español | Key Fact |
|---|---|---|
| Air compressor | Compresor de aire | Pumps air into the system; driven by engine |
| Governor | Regulador / Gobernador | Controls cut-in (~100 PSI) and cut-out (~125 PSI) |
| Air tanks / Reservoirs | Tanques / Depósitos de aire | Store compressed air; must be drained daily |
| Drain valve | Válvula de drenaje | Manual or automatic; removes moisture from tanks |
| Safety valve | Válvula de seguridad | Opens at 150 PSI to prevent overpressure |
| Dual air system | Sistema de aire dual | Two separate systems — primary (rear) and secondary (front) |
| Service brakes | Frenos de servicio | Normal brakes applied by foot pedal |
| Parking brakes | Frenos de estacionamiento | Applied by yellow diamond-shaped control |
| Emergency brakes / Spring brakes | Frenos de emergencia / Frenos de resorte | Activate automatically when air pressure drops |
| English Term | Español | Key Fact |
|---|---|---|
| Slack adjuster | Ajustador de holgura | Connects brake chamber rod to brake cam |
| Pushrod | Varilla de empuje | Transfers air pressure to slack adjuster |
| Pushrod stroke | Carrera de la varilla de empuje | Distance pushrod travels — must not exceed legal limit |
| Brake drum | Tambor de freno | Rotating part that brake shoes press against |
| Brake lining | Forro del freno / Pastilla de freno | Friction material on brake shoes |
| S-cam brakes | Frenos de leva en S | Most common type of air brake system |
| Brake fade | Pérdida de eficacia / Fade de frenos | Reduction in braking caused by overheating |
| English Term | Español | How to Test |
|---|---|---|
| Low air warning test | Prueba de advertencia de baja presión | Fan brakes down; warning must activate by 60 PSI |
| Spring brake test | Prueba de frenos de resorte | Continue fanning; brakes must engage at 20-45 PSI |
| Air leakage test | Prueba de fuga de aire | Brakes applied; max 3 PSI/min drop (single), 4 PSI/min (combo) |
| Applied leakage test | Prueba de fuga con frenos aplicados | Engine off, brakes applied; check needle for movement |
Sample Exam Questions / Preguntas de Práctica
"At what air pressure should the low air warning device activate?"
✓ Answer: At 60 PSI or lower
En español: ¿A qué presión de aire debe activarse el dispositivo de advertencia de baja presión? → A 60 PSI o menos.
"What is the maximum leakage rate for a combination vehicle with brakes applied during the air leakage test?"
✓ Answer: 4 PSI per minute
En español: ¿Cuál es la fuga máxima permitida para un vehículo combinado con frenos aplicados? → 4 PSI por minuto.
"What does the governor control in an air brake system?"
✓ Answer: The air compressor cut-in and cut-out pressure
En español: ¿Qué controla el regulador (governor)? → La presión de corte inferior y superior del compresor de aire.
The Air Brakes exam has a higher failure rate than any other CDL section — primarily because of vocabulary. When you know what "dual air system," "pushrod stroke," and "spring brakes" mean in English, the questions become logical rather than confusing. Study the vocabulary first. Then practice the questions. That sequence works.
Master the Full Air Brakes Section
CDL English Pro's Air Brakes module covers all 80+ terms with bilingual audio, interactive flashcards, and 100+ practice questions formatted like your state exam.
Ver Programas / See Courses →Ready to start training?
Find out your CDL English level in 5 minutes — free, bilingual, no sign-up required.
Take the free CDL English quiz →