A timber lorry or log truck is a large truck used to carry logs. Some have integrated flatbeds, some are discrete tractor units, and some are configured to spread a load between the tractor unit and a dollied trailer pulled behind it. Often more than one trailer is attached.
There are two main types of modern logging trucks — those used on rough ground and trails in the forest where they are felled and those used for transport on normal highways and roads. Because the roads in forests are rough and often temporary, the suspension and tires of an offroad truck are especially significant. Solid, low pressure and high pressure tires have been used. As many as nine axles may be used to provide low ground pressure and good traction.
Timber is commonly grown in hilly country unsuitable for farming and so the ability of a log truck to climb a gradient is significant. The steepness depends on the quality of the surface – mud and snow are harder to climb than gravel and soil. For a manageable gradient, the speed will then depend upon the power of the truck. The legal weight limits will vary by jurisdiction but, for example, in the southern states of the USA, they range from 80,000 to 88,000 pounds (36,300 to 39,900 kg) — about 40 short tons (35.7 long tons; 36.3 t).
To load the logs, the truck may be fitted with one or more winches or cranes. The logs are commonly unloaded by letting them roll off sideways.
Manufacturers of log trucks include Hayes Truck, Kenworth, Scania AB, and Volvo.