Illinois CDL Doubles and Triples cheat sheet

A converter dolly is a separate towed vehicle: frame, fifth wheel, one or two axles, drawbar eye, safety chains, brake chambers, shut-off valves and couplers. It gets its own full pre-trip inspection, not a glance.

Pintle hook: the latch must close completely over the drawbar eye, the safety pin or latch must be secured, and the hook throat must show no cracks, deep grooves or elongation from wear.

Fifth wheel checks (tractor and dolly): locking jaws closed around the kingpin, release handle pushed in with the safety latch engaged, no gap between the plate and the trailer apron, plate greased, mounting bolts tight, no cracks in plate or brackets.

Drawbar and A-frame: inspect for cracks, bends, damaged welds and a worn eye; the drawbar must pivot freely and must not contact the tires, frame or air lines at full turn.

Safety chains: attached at both ends, routed so they can catch a dropped drawbar, not dragging on the pavement, no broken links, stretched hooks or badly worn clevis pins.

Dolly spring brake: with the dolly uncoupled, its spring brake must hold it on a grade; the chamber, pushrod and slack adjuster must stroke and return without sticking.

Tires and wheels on every trailer and dolly axle: matched duals, no cuts or bulges, no missing or loose lug nuts, valve stems and caps present, tread at or above the legal minimum for that position.

Landing gear on each trailer: fully raised, crank secured, both feet intact, no bent legs or missing cross bracing.

Each trailer frame and undercarriage: cross members, sills, floor, rear impact guard, mud flaps, rear shut-off valves and electrical receptacle all present and undamaged.

The converter dolly converts one trailer into a double: its drawbar eye latches into the pintle hook on the rear frame of the lead trailer, and its fifth wheel carries the kingpin of the trailer behind it.

Standard connection order: chock or set the dolly brake, latch the pintle hook and safety pin, attach the safety chains, connect the dolly's red and blue air lines from the rear of the lead trailer, charge the system, then back the dolly's fifth wheel under the rear trailer's kingpin.

Gladhand code: red is the emergency/supply line that charges the trailer tanks and releases the spring brakes; blue is the service line that carries the brake application signal. Match red to red and blue to blue.

A crossed connection (blue to red) leaves the following trailer without working service brakes or with the spring brakes locked; check the color of every coupler, not just the first one.

The dolly fifth wheel is a load-carrying coupling: the kingpin must be fully seated, the jaws closed and the handle latched before the combination is moved even a few feet.

Dead-end shut-off valves at the rear of each trailer and on the dolly must be closed when nothing is attached; an open valve bleeds supply air and sets the spring brakes.

Safety chains are the secondary attachment and carry load only if the pintle hook or drawbar fails; they must be short enough not to drag but long enough not to restrict turning.

The dolly carries no cargo and no brakes of its own to stop the load behind it at speed; it supports and steers the rear trailer, and the rear trailer's own brakes do the stopping.

Route and support every air line and cord in the dummy couplers and holders so nothing kinks, chafes on the frame, or contacts the exhaust or tires.

Charge the emergency (red) line as the system builds; the trailer spring brakes release only after supply pressure reaches roughly 45 to 60 psi.

Static leak test, combination vehicle: engine off, system fully charged to governor cut-out (about 120 to 125 psi). With the brakes released, loss must not exceed 4 psi in one minute. With the brake pedal fully applied and held, loss must not exceed 6 psi in one minute.

Single-vehicle reference values for the same test are 3 psi (released) and 4 psi (applied) in one minute; a combination is allowed slightly more because of the extra lines and chambers.

Low-pressure warning: the buzzer and light must activate before system pressure drops below 60 psi. Trailer spring brakes normally pop out between 20 and 45 psi.

Tractor protection valve: controlled by the red trailer air supply knob, it seals the tractor's air system and applies the trailer spring brakes during a breakaway or major leak.

Spring brake test: with the system charged and the engine off, pull the red knob out and listen for the exhaust as the trailer brakes set; push it in and they release once supply pressure rebuilds.

Gladhand inspection: gaskets present and not torn, coupler locking tabs intact, no cracks in the rubber, lines long enough for a full turn but not hanging low.

With the combination fully charged and the engine off, listen along each unit; a steady hiss is a leak that must be found and repaired before dispatch, not logged for later.

Dolly air routing: supply and service air pass from the lead trailer's rear shut-off valves to the dolly, then to the rear trailer; each trailer's own tanks operate its own brakes.

SAE seven-way pin colors: white is ground, brown is tail/marker/clearance, yellow is left turn, green is right turn, red is stop (separate stop circuit), blue is auxiliary, black is ABS.

The cord runs tractor to lead trailer, then through the dolly to the last trailer; every plug must be fully seated and every receptacle cover closed to keep out water and road salt.

Check on each unit separately: clearance and marker lamps, tail lamps, left and right turn signals, four-way flashers, stop lamps and the rear identification lamps (three on top).

Trailer ABS lamp: it should light at key-on and go out once speed exceeds about 5 mph; a lamp that stays lit means an ABS fault on that unit.

A cord that drags or rubs the frame, dolly or landing gear wears through the insulation, causing shorts, blown fuses and total loss of trailer lighting.

Support the cord in the spring-loaded holder or dummy socket when it is not connected so the pins stay clean and the plug does not fill with dirt and moisture.

Trailers 80 inches or more in overall width require clearance lamps at the widest point and identification lamps at the rear; a burned-out marker makes the combination illegal to run.

Before moving, turn on the four-way flashers and walk the full combination to confirm every lamp on every unit is working, including the last trailer's rear lamps.

Aggregate working load limit: the total WLL of all tiedowns used on an article must be at least 50 percent of the weight of that article, and each component must be marked with its rating.

Tiedown count rule: up to 5 feet long and up to 1,100 pounds needs one tiedown; up to 5 feet and 1,101 to 2,200 pounds needs two; over 5 feet up to 1,100 pounds needs two.

Ten-foot formula: for articles longer than 10 feet or heavier than 2,200 pounds, use at least one tiedown per 10 feet of length (rounded up) AND aggregate WLL of at least 50 percent of the weight.

A single tiedown component rated above 5,500 pounds WLL is not counted beyond that cap when satisfying the aggregate-WLL rule for ordinary articles.

Cargo must be secured against forward movement with a headerboard, blocking or tiedowns, and also against rearward and lateral movement during braking and turns.

Recheck securement within the first 50 miles of driving and again every 3 hours or 150 miles, whichever comes first, and after any hard braking or evasive action.

Keep every trailer within its axle and gross ratings and check axle weights at a scale; a lightly loaded lead trailer with a heavy rear trailer degrades handling and lengthens stopping distance.

Do not load cargo against the rear doors, the air lines, the electrical cord or the kingpin area; the dolly drawbar and pintle hook need clear space to pivot.

The converter dolly is not a cargo platform; it carries only the kingpin load of the trailer behind it and must never be loaded with freight.

Coupling order for doubles: set the dolly spring brake, align the tractor and lead trailer with the dolly, latch the pintle hook and safety pin, attach the safety chains, connect the red and blue lines, charge the system, back the dolly fifth wheel under the rear trailer's kingpin, tug test, then connect the rear trailer's air lines and light cord.

Before backing under any trailer, check the height: the trailer apron must meet the fifth wheel plate, not ride above it. If the trailer is too high, the kingpin can pass over the plate and the trailer drops when pulled forward.

Tug test: with the trailer brakes set (or the red knob pulled out), pull forward gently in the lowest gear. A locked coupling holds firm; a bad one releases with a clunk and forward movement.

Visual check after coupling: jaws closed around the kingpin, no daylight between the fifth wheel plate and the apron, release handle pushed fully in with the safety latch engaged, no lines pinched in the coupling.

Uncoupling order for doubles: set the parking brakes on the rear trailer and dolly, disconnect the rear trailer's light cord and air lines, release the dolly fifth wheel, pull forward clear, then disconnect the dolly chains, air lines and pintle hook.

Never uncouple with the trailer spring brakes released, and never drop a trailer on a grade without chocking the wheels first.

After uncoupling, close all shut-off valves, place the couplers in the dummy holders, close the receptacle cover and secure the light cord.

When dropping the final trailer, lower the landing gear until it contacts the ground and supports the load before releasing the fifth wheel.

Off-tracking: the rear wheels of the last trailer follow a path inside the path of the front wheels; the amount grows with the number of trailers, the length of the units and the sharpness of the turn.

Rearward amplification: in a quick lane change or evasive steer, the last trailer swings farther sideways and faster than the tractor. It is greatest with triples and smallest with a single trailer.

Right turns: swing wide enough that the last trailer's tires clear the curb, but not so wide that you enter another traffic lane. Watch the last trailer in the right mirror and check for pedestrians and cyclists on the right side.

Following distance: a loaded combination needs more room to stop than a single, and the rear trailer can swing into the adjacent lane, so leave a gap large enough for both.

Downgrades: select a gear that holds a safe speed at the top of the grade and use snub braking in short, firm applications; continuous light braking overheats drums and produces fade.

Lane changes: signal early, check both mirrors, and remember the last trailer is the last unit to clear the lane you are leaving.

Total weight, not axle count, drives stopping distance; the heavier the combination, the longer the distance required at any given speed.

Backing a set of doubles or triples is unpredictable because the dolly adds an extra pivot point; plan routes so backing is avoided, and when unavoidable back in as straight a line as possible.