Truck & Car Guides / Trucks explained
Trucks explained
How a semi truck is put together, what the weight classes mean, and how the engine, gearbox and brakes move and stop 80,000 pounds.
A tractor-trailer looks simple from the outside: a cab, a long box and a lot of wheels. Underneath, it is a carefully balanced system of axles, air lines, a big diesel engine and brakes designed to stop a load that can weigh as much as 20 or more passenger cars. Start here to learn the parts and the vocabulary.
TrucksDiesel engine basics for trucksDiesels squeeze air until it is hot enough to ignite fuel without a spark. That simple idea gives trucks huge torque, long engine life and good fuel economy.
TrucksHow air brakes workHeavy trucks stop with compressed air, not brake fluid. Here is how the compressor, tanks, chambers and spring brakes work together, and why the system fails safe.
TrucksJake brakes and engine brakingThat loud rapid-fire roar from a truck coming down a hill is the engine brake at work. Here is how it slows the truck without wearing out the brakes, and why some towns restrict it.TrucksSemi truck anatomy, part by partA tractor-trailer is two vehicles joined at a single pin. Here is what every major part does, from the steer axle to the trailer's landing gear.
TrucksSleeper cab vs day cabSleeper cabs are rolling apartments for drivers who are out for days or weeks. Day cabs are lighter and nimbler for drivers who sleep at home. Here is how they compare.
TrucksTruck classes 1 to 8 explainedIn the US, trucks are grouped into eight classes by gross vehicle weight rating. Here is what each class means, with examples and a full table.
TrucksTruck transmissions, from 10-speeds to automated manualsWhy big trucks need so many gears, how a manual truck gearbox differs from a car's, and why automated manuals have taken over new truck sales.
TrucksHow air brakes workHeavy trucks stop with compressed air, not brake fluid. Here is how the compressor, tanks, chambers and spring brakes work together, and why the system fails safe.TrucksJake brakes and engine brakingThat loud rapid-fire roar from a truck coming down a hill is the engine brake at work. Here is how it slows the truck without wearing out the brakes, and why some towns restrict it.TrucksSemi truck anatomy, part by partA tractor-trailer is two vehicles joined at a single pin. Here is what every major part does, from the steer axle to the trailer's landing gear.TrucksSleeper cab vs day cabSleeper cabs are rolling apartments for drivers who are out for days or weeks. Day cabs are lighter and nimbler for drivers who sleep at home. Here is how they compare.TrucksTruck classes 1 to 8 explainedIn the US, trucks are grouped into eight classes by gross vehicle weight rating. Here is what each class means, with examples and a full table.TrucksTruck transmissions, from 10-speeds to automated manualsWhy big trucks need so many gears, how a manual truck gearbox differs from a car's, and why automated manuals have taken over new truck sales.