Fifth Wheel

CDL written test practice for iPhone and iPad

Know why the answer is right.

Every answer explained, with the manual section to read.

Fifth Wheel is practice for the CDL written knowledge tests: General Knowledge, Air Brakes, Combination Vehicles and the endorsements. Every question tells you why the right answer is right, why the other choices are wrong, and where to look it up in your CDL manual.

All of General Knowledge is free, plus one full practice exam in every other section. Pro is $19.99 once. No account. No ads. No subscription.

Coming soon to the App Store
Air Brakes · exam reviewExample

During the final air brake check, the low air pressure warning should turn on before tank pressure falls below about how much?

  1. About 20 psi
  2. About 55 psi
  3. About 85 psi
  4. About 100 psi

Why: The warning has to come on while the tank still holds at least 55 psi, so you find out about an air loss early enough to stop safely. 100 psi is roughly where the governor starts the compressor again, 85 psi is where the buildup-rate test begins, and 20 psi is at the low end of the range where the spring brakes come on.

CDL Manual §5.3.3 Step 7 Final Air Brake Check

Sections and practice exams Each practice exam is built like the knowledge test it prepares you for. 80% is a pass in every section.
SectionExam lengthPass markFree
General Knowledge50 questions80%Whole section
Air Brakes25 questions80%One full exam
Combination Vehicles20 questions80%One full exam
Endorsements
Hazardous Materials30 questions80%One full exam
Tank Vehicles20 questions80%One full exam
Doubles and Triples20 questions80%One full exam
Passenger Vehicles20 questions80%One full exam
School Bus20 questions80%One full exam

Exam length and pass mark follow the model CDL manual most states use; your state's test can differ. The App Store page lists the sections included in the current version of the app.

What you get

  1. Every answer explained

    After each question: why the right answer is right, and why each other choice is wrong. No bare answer keys.

  2. The manual section, every time

    Each explanation names the section to read, like "CDL Manual §5.3.3 Step 7 Final Air Brake Check". Numbers follow the model manual most states use; some state editions number a few sections differently, so the title is always shown too.

  3. Full-length practice exams

    The same length and pass mark as the knowledge tests in the model manual. An optional timer is there when you want it; it starts off.

  4. Review every mistake

    Right after each exam, go through every question you missed, with its explanation. Mistake review is always free. Retrying just those is free in General Knowledge and part of Pro in the other sections.

  5. Know when you're ready

    Progress by section and topic, your weak topics, exam history and a day streak. A section shows Ready when your last three exams in it are 80% or better.

  6. Weak-topic marathon Pro

    A run of questions from the topics you miss most, across sections, until you get them right.

  7. Pre-trip inspection checklist

    A step-by-step walk-around checklist, written in plain words, to practice the inspection routine.

  8. Offline and private

    Works with no signal. Progress syncs through your own iCloud. One optional study reminder. Free widgets for readiness, a question of the day and your streak. With Pro, export a progress PDF.

Pricing

Free$0
  • The whole General Knowledge section
  • One full practice exam in every other section
  • Mistake review after every exam, always
  • Widgets: readiness, a question of the day, your streak
  • No account, no ads
Pro$19.99 once
  • All sections and endorsements
  • Unlimited practice exams
  • Retry missed questions in every section
  • Weak-topic marathon
  • Progress PDF export
One-time purchase. No subscription, no trial timer.

Plain promises

One price, once

Pro is $19.99, paid one time. No subscription, no weekly plan, no countdown offers.

No ads, ever

No ads, no analytics, no tracking and no account. The Pro screen shows only when you open a Pro feature.

Your progress stays yours

It lives on your device and, if you like, in your own private iCloud. We can't see it.

Written by us. Questions and explanations are our own, checked against public state CDL manuals. We cite section numbers and titles; we don't reproduce manual text. Your state's CDL manual is the final word on its own rules.