Crawl ratio
Encyclopedia
Crawl ratio is a term used in the automotive world to describe the lowest gear ratio
a vehicle is capable of. The crawl ratio of a vehicle is affected by the entire drive train, including transmission
, overdrive differential
and tire
s, and can vary greatly between automobiles.
The lowest gear of most vehicles is either first gear or reverse, but when referring to crawl ratios, only first is normally taken into consideration. The crawl ratio is aptly named, for when a car is using its lowest possible gearing, it moves the slowest at a particular engine rpm. The usefulness of a high crawl ratio is to provide the driver with the greatest possible torque
to pull large loads or climb steep inclines. Crawl ratios are most often used in the context of large SUVs or trucks and off-road vehicles.
Gear ratio
The gear ratio of a gear train is the ratio of the angular velocity of the input gear to the angular velocity of the output gear, also known as the speed ratio of the gear train. The gear ratio can be computed directly from the numbers of teeth of the various gears that engage to form the gear...
a vehicle is capable of. The crawl ratio of a vehicle is affected by the entire drive train, including transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...
, overdrive differential
Differential (mechanics)
A differential is a device, usually, but not necessarily, employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it...
and tire
Tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...
s, and can vary greatly between automobiles.
The lowest gear of most vehicles is either first gear or reverse, but when referring to crawl ratios, only first is normally taken into consideration. The crawl ratio is aptly named, for when a car is using its lowest possible gearing, it moves the slowest at a particular engine rpm. The usefulness of a high crawl ratio is to provide the driver with the greatest possible torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
to pull large loads or climb steep inclines. Crawl ratios are most often used in the context of large SUVs or trucks and off-road vehicles.