FL CDL Doubles/Triples cheat sheet

Coupling order: back the tractor under the first (lead) trailer, lock the fifth wheel, then set the converter dolly under the lead trailer's rear and connect the dolly's upper coupler plate to the lead trailer's kingpin.

Uncoupling order is the reverse of coupling: release the dolly from the lead trailer before releasing the lead trailer from the tractor, and chock all wheels on every trailer before releasing any coupling.

A converter dolly carries its own fifth wheel plate at the rear and a kingpin plate at the front; the lead trailer's rear kingpin drops into the dolly's fifth wheel, and the rear trailer's kingpin locks into the dolly's rear fifth wheel.

Check the fifth wheel jaw lock by tugging the tractor gently forward against a locked trailer brake (a "tug test") before releasing the tractor parking brake; a proper lock holds the trailer without separation.

Confirm the fifth wheel is fully greased and the jaws close around the kingpin shank, not the kingpin head; a high hitch means the jaws are riding on top of the kingpin and the coupling is unsafe.

Connect the dolly's air lines (emergency/red and service/blue) and electrical cord to the lead trailer's gladhands; the dolly's spring brakes release only when the emergency line is charged.

After coupling, raise the landing gear fully and secure the crank handle; a partially lowered dolly landing gear can strike the road or drag on railroad crossings.

Verify safety latches on the fifth wheel release handle and on the dolly's upper coupler are closed and pinned, and that the dolly's air tank is charged to release its spring brakes.

Walk-around sequence: start at the tractor front, work down the driver side, cross to the passenger side, check the rear of each trailer, and inspect the dolly from both sides and underneath.

Inspect the dolly's frame for cracks at the upper coupler plate and at the fifth wheel mounting; dolly frames and kingpin plates crack under repeated coupling loads.

Check every trailer's kingpin for wear, gouges, and bent flanges; a worn or damaged kingpin will not lock securely in the fifth wheel jaws.

Confirm the dolly's safety chains are attached to the lead trailer's frame or to the dolly frame as required, and that the chains are not twisted or dragging.

Check air line gladhand seals (rubber O-rings) for cracks and missing seals; a leaking seal causes the emergency line to lose pressure and can set the spring brakes.

Verify the dolly's spring brake chambers, slack adjusters, and pushrod travel; excessive pushrod travel means the brakes are out of adjustment and the vehicle is out of service.

Check the electrical cord and plug for chafed insulation and corroded pins; the dolly's ABS and marker lights depend on a clean connection.

Inspect all tires on every trailer and the dolly for tread depth, sidewall damage, and matching inflation; under-inflated duals overheat and can fail.

Off-tracking increases with each additional trailer: a doubles combination cuts corners more sharply than a single, and triples cut even more, so swing wide on every turn.

Rearward amplification (the "crack-the-whip" effect) grows with speed and with the number of trailers; the last trailer in a set can swing far outside the path of the tractor during a rapid lane change.

When backing, only the rearmost trailer responds predictably; steering input moves the last trailer opposite the direction of the steering wheel, so back slowly and use a spotter.

On a right turn, the tractor's rear wheels and the dolly cut inside the tractor's front wheel path; watch the mirrors for the dolly and rear trailer clearing curbs and poles.

A converter dolly pivots independently, so a sudden steering correction can cause the dolly to swing laterally and jackknife the combination; make smooth, small steering inputs.

Trailer length and number determine the turning radius: a triples set needs a wider turn than a doubles set, and the pivot point of each trailer differs.

Check mirror adjustment before moving: you must see the dolly wheels and the rear trailer's side in the mirrors to monitor tracking through turns.

At highway speed, the rear trailer tracks closest to the tractor path; at low speed in tight turns, the rear trailer cuts the corner most severely.

Stopping distance grows with the number of trailers because total combination weight increases while braking force is shared; allow at least one second of following distance per ten feet of vehicle length plus speed.

The emergency (red) line charges the trailer air tanks and releases spring brakes; a loss of emergency line pressure applies the spring brakes on all trailers automatically.

The service (blue) line carries the brake application signal; a broken service line means the trailers will not brake when the treadle is applied, even though the emergency line still holds pressure.

Use the trailer hand valve (trolley valve) only for testing trailer brakes, never for parking or for normal stopping; it applies only the trailer brakes and can cause a jackknife.

Brake application must be smooth and progressive on a multi-trailer combination; a hard, sudden application causes the rear trailers to push the tractor and can fold the combination.

Check brake adjustment on every trailer and the dolly; a combination with out-of-adjustment brakes on one trailer pulls to that side and lengthens stopping distance.

When descending a long grade, select a low gear before the descent and use engine braking; continuous service brake use overheats drums and fades the brakes on all units.

On a downgrade, brake firmly enough to feel the retarder or engine brake holding, then release; light continuous pressure is what causes fade and brake failure.

Crosswinds affect the rear trailer most: a sudden gust can push the last trailer sideways and start a sway that amplifies forward through the combination; slow down and grip the wheel firmly.

Speed is the dominant factor in rearward amplification; reducing speed in a lane change or curve is the single most effective way to keep the last trailer in its lane.

On wet or icy pavement, reduce speed and increase following distance; the dolly's light weight makes it prone to sliding and jackknifing on slick surfaces.

Before a railroad crossing, stop and check that the dolly's landing gear is fully raised and that no part of the combination will drag on the rails.

When passing, check that the entire combination, including the last trailer, has cleared the passed vehicle before returning to the lane; the rear trailer is the last to clear.

In strong wind or on a narrow bridge, keep both hands on the wheel and avoid sudden steering; a rapid correction on a multi-trailer set can induce trailer sway.

If the combination starts to sway, release the accelerator and steer straight; do not brake hard, because hard braking transfers weight forward and worsens the sway.

Parking on a grade requires chocking wheels on every trailer and the dolly, and setting the tractor parking brake; spring brakes alone may not hold a heavy combination.

Coupling order: back the tractor under the first (lead) trailer, lock the fifth wheel, then set the converter dolly under the lead trailer's rear and connect the dolly's upper coupler plate to the lead trailer's kingpin.

Uncoupling order is the reverse of coupling: release the dolly from the lead trailer before releasing the lead trailer from the tractor, and chock all wheels on every trailer before releasing any coupling.

A converter dolly carries its own fifth wheel plate at the rear and a kingpin plate at the front; the lead trailer's rear kingpin drops into the dolly's fifth wheel, and the rear trailer's kingpin locks into the dolly's rear fifth wheel.

Check the fifth wheel jaw lock by tugging the tractor gently forward against a locked trailer brake (a "tug test") before releasing the tractor parking brake; a proper lock holds the trailer without separation.

Confirm the fifth wheel is fully greased and the jaws close around the kingpin shank, not the kingpin head; a high hitch means the jaws are riding on top of the kingpin and the coupling is unsafe.

Connect the dolly's air lines (emergency/red and service/blue) and electrical cord to the lead trailer's gladhands; the dolly's spring brakes release only when the emergency line is charged.

After coupling, raise the landing gear fully and secure the crank handle; a partially lowered dolly landing gear can strike the road or drag on railroad crossings.

Verify safety latches on the fifth wheel release handle and on the dolly's upper coupler are closed and pinned, and that the dolly's air tank is charged to release its spring brakes.

Walk-around sequence: start at the tractor front, work down the driver side, cross to the passenger side, check the rear of each trailer, and inspect the dolly from both sides and underneath.

Inspect the dolly's frame for cracks at the upper coupler plate and at the fifth wheel mounting; dolly frames and kingpin plates crack under repeated coupling loads.

Check every trailer's kingpin for wear, gouges, and bent flanges; a worn or damaged kingpin will not lock securely in the fifth wheel jaws.

Confirm the dolly's safety chains are attached to the lead trailer's frame or to the dolly frame as required, and that the chains are not twisted or dragging.

Check air line gladhand seals (rubber O-rings) for cracks and missing seals; a leaking seal causes the emergency line to lose pressure and can set the spring brakes.

Verify the dolly's spring brake chambers, slack adjusters, and pushrod travel; excessive pushrod travel means the brakes are out of adjustment and the vehicle is out of service.

Check the electrical cord and plug for chafed insulation and corroded pins; the dolly's ABS and marker lights depend on a clean connection.

Inspect all tires on every trailer and the dolly for tread depth, sidewall damage, and matching inflation; under-inflated duals overheat and can fail.

Off-tracking increases with each additional trailer: a doubles combination cuts corners more sharply than a single, and triples cut even more, so swing wide on every turn.

Rearward amplification (the "crack-the-whip" effect) grows with speed and with the number of trailers; the last trailer in a set can swing far outside the path of the tractor during a rapid lane change.

When backing, only the rearmost trailer responds predictably; steering input moves the last trailer opposite the direction of the steering wheel, so back slowly and use a spotter.

On a right turn, the tractor's rear wheels and the dolly cut inside the tractor's front wheel path; watch the mirrors for the dolly and rear trailer clearing curbs and poles.

A converter dolly pivots independently, so a sudden steering correction can cause the dolly to swing laterally and jackknife the combination; make smooth, small steering inputs.

Trailer length and number determine the turning radius: a triples set needs a wider turn than a doubles set, and the pivot point of each trailer differs.

Check mirror adjustment before moving: you must see the dolly wheels and the rear trailer's side in the mirrors to monitor tracking through turns.

At highway speed, the rear trailer tracks closest to the tractor path; at low speed in tight turns, the rear trailer cuts the corner most severely.

Stopping distance grows with the number of trailers because total combination weight increases while braking force is shared; allow at least one second of following distance per ten feet of vehicle length plus speed.

The emergency (red) line charges the trailer air tanks and releases spring brakes; a loss of emergency line pressure applies the spring brakes on all trailers automatically.

The service (blue) line carries the brake application signal; a broken service line means the trailers will not brake when the treadle is applied, even though the emergency line still holds pressure.

Use the trailer hand valve (trolley valve) only for testing trailer brakes, never for parking or for normal stopping; it applies only the trailer brakes and can cause a jackknife.

Brake application must be smooth and progressive on a multi-trailer combination; a hard, sudden application causes the rear trailers to push the tractor and can fold the combination.

Check brake adjustment on every trailer and the dolly; a combination with out-of-adjustment brakes on one trailer pulls to that side and lengthens stopping distance.

When descending a long grade, select a low gear before the descent and use engine braking; continuous service brake use overheats drums and fades the brakes on all units.

On a downgrade, brake firmly enough to feel the retarder or engine brake holding, then release; light continuous pressure is what causes fade and brake failure.

Crosswinds affect the rear trailer most: a sudden gust can push the last trailer sideways and start a sway that amplifies forward through the combination; slow down and grip the wheel firmly.

Speed is the dominant factor in rearward amplification; reducing speed in a lane change or curve is the single most effective way to keep the last trailer in its lane.

On wet or icy pavement, reduce speed and increase following distance; the dolly's light weight makes it prone to sliding and jackknifing on slick surfaces.

Before a railroad crossing, stop and check that the dolly's landing gear is fully raised and that no part of the combination will drag on the rails.

When passing, check that the entire combination, including the last trailer, has cleared the passed vehicle before returning to the lane; the rear trailer is the last to clear.

In strong wind or on a narrow bridge, keep both hands on the wheel and avoid sudden steering; a rapid correction on a multi-trailer set can induce trailer sway.

If the combination starts to sway, release the accelerator and steer straight; do not brake hard, because hard braking transfers weight forward and worsens the sway.

Parking on a grade requires chocking wheels on every trailer and the dolly, and setting the tractor parking brake; spring brakes alone may not hold a heavy combination.