Rock climbing with an off-road truck is pretty exciting, although it can be dangerous as well. Success and safety depend on having the right performance equipment like rock climbing tires, taller shocks, and winch ready bumpers as well as knowing what your truck can do. To figure all that out, drivers need to understand crawl ratio, how it is generated, and how to get the most benefit from it for rock climbing.
What Is Crawl Ratio?
Crawl ratio is the ratio of torque applied at the wheels in comparison to what is applied at the flywheel. This ratio defines the way torque is increased moving from the drivetrain to the wheels that will propel them forward under different conditions. It is determined based on the power generated by the transmission, the transfer case, and the differential.
As such, the high-speed power passing to the transmission passes through the transfer case, then into the differential where it is converted into the lower-speed torque required to turn the wheels. Velocity is exchanged for power.
Getting Over Rocks Demands More Than Crawl Ratio
Those with off-road trucks used for rock climbing want the greatest amount of torque delivered to the wheels in the most efficient way. While a high crawl ratio is important, it’s not the only factor required for successfully getting over big rocks. Doing so also involves engine torque as well as the amount of force tires exert on the ground. All three must work together to produce the highest total torque that can propel the truck over big obstacles.
The Effect of Torque
To measure or predict crawl ratio, it’s important to understand the amount of torque the engine is generating. To understand how well your prized off-road truck outfitted with steel truck bumpers will handle the big climbs, you must understand how engine torque is being multiplied against the crawl ratio. Ideally, a lower engine torque producing a higher torque at the wheels is most efficient, leaving room to increase torque even more by revving the engine to increase torque.
Besides engine torque, truck owners also need to consider how their tires affect the crawl ratio and overall torque for climbing. Tires essentially absorb some of the torque required to propel the vehicle forward, so gearing needs to account for this loss in actual torque applied against the ground. Smaller tires reduce this factor less than larger ones; however, rock climbing requires taller, heavier tires with chunkier treads - and taller, bigger tires need more torque to turn them.
Calculate The Correct Crawl Ratio
Considering both of these additional factors, truck owners need to first determine their crawl ratio, then re-gear to account for the size and weight of their tires. In doing so, they will achieve the highest crawl ratio possible for their vehicle, which will provide greater torque to the wheels. Resulting crawl ratio will also dictate how fast the truck can travel in 4-wheel low, as well as what the minimum speed will be before the engine stalls.
These calculations certainly seem complicated at first; however, taking the time to figure them out will help determine the amount of power getting to your wheels and how to take advantage of available torque when climbing large obstacles. So add those steel bumpers and winch bumpers - recalculate - and know what you need to climb those big rocks with your rock-crawling off-road truck!