The MythBusters The MythBusters

MythBusters Episode 80: Big Rig Myths

Premier Date: June 6, 2007

A tire on a big rig can explode with lethal force.

confirmed

The MythBusters first tested whether a big rig tire could actually explode. They managed to obtain several truck tires and subjected them to actual road conditions, to try to replicate certain circumstances that could cause a tire to explode. Although they could not make a tire fail catastrophically, they managed to cause it to disintegrate violently by running the tire flat at highway speed, though the flying debris failed to hit the dummy set up next to the tire. However, the MythBusters were able to measure the velocity the debris. Taking an actual piece of the exploded tire, the MythBusters launched it at its measured initial velocity into a pig spine-equipped ballistics gel dummy behind a car window. The piece of debris smashed through the window and literally decapitated the dummy, proving the myth was in fact possible.

Drafting behind a big rig will improve your car’s fuel efficiency.

confirmed

To test this myth, the build team procured a car, a big rig, and a device that could measure a car’s fuel efficiency. They then drove the car behind a moving big rig at various distances ranging from 100 to 2 feet and measured the amount of fuel the car consumed. The Build Team discovered that the closer the car was to the big rig, the less drag is produced, thus the more fuel saved. At just ten feet, the car managed to increase its fuel efficiency by 40%. Drafting at two feet was slightly lower than the ten foot distance, mainly because Grant had to keep working the car pedal to maintain distance from the truck. However, that did not dispute the fact that drafting actually can increase your car’s fuel efficiency. However, the Build Team has warned that drafting is incredibly dangerous because the truck driver may not able to see you and you may not be able to react in time if the truck were to make a sudden stop.

As seen in the TV series Knight Rider, a moving car can safely transition from a road into a moving big rig via ramp.

confirmed

To test this myth, the MythBusters first started with a small scale test using a toy car. Simulating the Knight Rider stunt, the MythBusters found that the toy car could enter the big rig safely without a sudden and dangerous acceleration that many people had feared. They then tested the stunt at full scale using a Chevy Camaro, the rebadged version of the Pontiac Trans Am used in Knight Rider. They tested at both 30 miles per hour and 55 miles per hour with no difficulty. The MythBusters explained that, even when hitting the car’s ramp, the car’s inertia keeps it going at the exact same speed relative to the ground — which lets it safely drive into the big rig, with no surprising accelerations. Jamie then reinforced the myth by safely exiting the moving semi truck in reverse. Also all of their experiments took place during a rain storm.

Cyclists can draft behind a big rig and achieve "crazy speeds".

plausible

the Build Team decided to test whether a cyclist would have an easier time riding if he were to draft a big rig. Tory was chosen as the cyclist and performed a control test by cycling up to 20 miles per hour unaided. To ensure accuracy, Grant kept track of Tory’s heart rate and Kari measured his speed via radar. By the end of the control run, Tory was exhausted by the effort. During the actual test, however, Tory literally coasted along behind the big rig and rarely had to pedal at all. Due to the obvious difference in performance and the fact that professional cyclists draft during competitions, the myth was plausible.