Oklahoma CDL Combination flashcards
Oklahoma CDL Combination · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Rollover threshold
- The lateral acceleration, usually expressed in g, at which a vehicle's inside tires lift off the ground. A loaded tractor-trailer typically rolls at about 0.35 to 0.45 g.
- Rearward amplification
- The tendency of a trailer's lateral motion to be larger than the tractor's during abrupt steering. It makes rapid lane changes especially likely to cause trailer rollover.
- Fifth wheel jaws
- The locking mechanism that grips the trailer kingpin. Before coupling, the jaws must be open and free of debris; after coupling, they must close fully around the kingpin.
- Tug test
- After coupling, pull forward gently in low gear against the trailer brakes. If the fifth wheel is locked, the trailer holds; if not, the trailer slides or the tractor pulls out.
- Glad hand connection
- The emergency supply line connects to the emergency glad hand and the service line to the service glad hand. Crossed lines cause trailer brakes to release or drag incorrectly.
- Trailer supply line
- The emergency line that charges the trailer air tanks. If supply pressure is lost, the tractor protection valve closes and the trailer spring brakes set automatically.
- Tractor protection valve
- A valve that isolates the tractor's air system from the trailer when trailer pressure drops below roughly 20 to 45 psi, preventing loss of tractor air.
- Brake lag distance
- The distance traveled during the roughly 0.4 to 0.6 second it takes air pressure to reach the brakes after the pedal is pressed. It adds to total stopping distance.
- Slack adjuster limit
- The maximum allowable push rod travel when the brakes are applied. Travel beyond the manufacturer's limit means the brakes are out of adjustment and the vehicle is out of service.
- ABS warning lamp
- An amber lamp that should light at startup and go out above about 4 mph. If it stays on, ABS is disabled but normal brakes still work.
- ABS braking technique
- Hold firm, steady pressure on the brake pedal during a panic stop and do not pump the brakes. Pumping defeats the antilock system and lengthens stopping distance.
- Trailer ABS power
- Trailer ABS receives electrical power through the trailer light cord. A damaged cord can disable trailer ABS even when the tractor's ABS still works.
- Off-tracking
- The difference between the path of the front wheels and the path of the rear wheels. A tractor-trailer's rear wheels cut inside the turn, and longer wheelbases cut more.
- Off-tracking rule of thumb
- A combination vehicle can off-track by about 1 foot for every 10 feet of wheelbase in a 90-degree turn. A 50-foot wheelbase can cut about 5 feet inside.
- Tractor-trailer pivot point
- The rear axle of the tractor, not the fifth wheel. The trailer pivots around the tractor's rear wheels, so the trailer's rear swings outward on tight turns.
- Backing steering direction
- When backing a tractor-trailer, turn the steering wheel toward the direction you want the trailer's rear to go. The trailer moves opposite the tractor's front.
- GOAL
- Get Out And Look. A backing procedure in which the driver stops, exits the cab, and checks the area behind and around the trailer before continuing.
- Backing toward driver's side
- Backing toward the left side of the vehicle is preferred because the driver's side mirror gives a better view of the trailer's path and reduces the blind side.
- Jackknife
- A condition in which the tractor's rear wheels lock or lose traction and the trailer pushes the tractor around, folding the combination at the coupling point.
- Drive-wheel skid correction
- Release the brake or throttle and steer in the direction the rear of the tractor is sliding. Do not steer opposite the skid, which causes a secondary skid.
- Trailer skid correction
- If the trailer's rear swings out, steer in the direction of the trailer's slide to straighten the combination. Overcorrecting can cause a jackknife.
- Blowout response
- Hold the steering wheel firmly, avoid hard braking, and slow gradually while keeping the vehicle straight. A combination vehicle can swerve violently if the wheel is jerked.
- Federal axle weight limit
- 20,000 pounds on any single axle and 34,000 pounds on a tandem axle group on the Interstate System. Exceeding either limit is illegal even if gross weight is legal.
- Bridge formula
- A federal formula that limits the weight on any group of axles based on the number of axles and the distance between them. It prevents overloading short spans.
- Tiedown aggregate working load limit
- The combined working load limit of all tiedowns must be at least half the cargo weight, and the cargo must be secured against forward, rearward, and lateral movement.
- Load center of gravity
- The point where the load's weight is concentrated. Keeping it low and centered improves stability and raises the roll threshold; a high or offset load lowers it.
- Following distance rule
- Allow at least one second per 10 feet of vehicle length at speeds under 40 mph, plus one second. A 60-foot rig needs about 7 seconds.
- Downgrade speed control
- Select a gear that holds the desired speed without braking. Use intermittent firm braking rather than continuous light braking to avoid brake fade.
- Scanning ahead
- Look 12 to 15 seconds ahead of the vehicle and check mirrors every 5 to 8 seconds. This gives time to react to brake lights, merges, and debris.
- Total stopping distance
- The sum of perception distance, reaction distance, brake lag distance, and effective braking distance. A loaded tractor-trailer may need 300 feet or more at highway speed.
- Trailer spring brakes
- Spring-applied brakes that set automatically when trailer air supply is lost. They are the fail-safe that stops a trailer after a breakaway or line separation.
- Tire tread minimums
- At least 4/32 inch tread depth on front steer tires and 2/32 inch on all other tires. Dual tires should match within 1/4 inch in diameter.