2009 Range Rover Sport Off-Road

Driving on the ubiquitous tarmac does not really require the use of both feet through everyday traffic, unless of course the vehicle has a manual gearbox. Since the left foot is not always being used while piloting an automatic, it sometimes gets forgotten while in off-pavement scenarios. Using this lazy left foot alongside the application of the double-pedal technique can become invaluable skill while negotiating precarious terrain.

The Scenario

The considerably large tree root in the way of the trail is covered in mud and just so happens to intersect the rather deep rut that the vehicle currently resides. There is not sufficient room to drive around the root. And, there is no way to slowly crawl up and over it because the tires are absolutely loaded with mud: traction gets lost at every attempt.

To relinquish the warmth and comfort of the driver’s seat in order to attach pull-straps or winches in this situation would be preposterous. All the driver needs is to put his/her left foot into action with a little thing called preload. Setting the preload takes a fine balance of left/right foot pressure. However, it only takes a minute or two to learn and can be practiced on or off pavement for flawless future use.

Suspension Preload

With the front wheels going upward with more ease, the rest of the vehicle will follow up and over the troublesome obstacle.

The driver holds both the gas and the brake simultaneously. This adds engine torque to the drivetrain and suspension while keeping the vehicle from moving forward. Having the suspension already under a torqued load will keep it from cycling too deeply and will absorb the obstacle’s impact with much more stability when the gas is quickly applied. Preloading also drastically reduces driveline shock-load, where components go from no-torque to full-torque instantly. Shock-loads can be very damaging to parts like axle shafts, drive shafts, u-joints and even entire differentials.

Once the brake is firmly applied, the driver needs to add and maintain engine torque until the vehicle “raises” up. Making the RPM’s of the motor sail into the 6,000 range would be impractical and potentially damaging. Yet, having an engine speed only slightly above idle, will not get the job done. So, the pilot needs to find the proper amount of both gas and brake. This is where practice on pavement comes into play.  

Let’s Do Launch Sometime

After the vehicle “raises” as high as the suspension will allow it, the driver knows that the maximum efficiency of torque has been applied to the driveline. Adding more torque at this stage will overpower the brakes and cause wheelspin. Reducing torque will bring the suspension off of its peak and lose effectiveness. Again, practice is key. With maximum torque applied, the driver will then quickly slip his/her left foot off of the brake while simultaneously pressing the throttle even more for the launch.

This vehicle-launching action is the desired effect when using double pedal and preload. Because the vehicle’s mass is already higher than what it was at rest, the suspension has much more ability for upward compression. With the front wheels going upward with more ease, the rest of the vehicle will easily follow up and over the troublesome tree root.

If the rear tire does not make it past the root though, the the preload and launch technique can be used once more to get the rest of the rig over.

Note of Caution

In this case, the root, will not be extremely detrimental to the undercarriage, however care still needs to be taken when the front wheel lands on the other side. A large rock, log, or even spare tire can be placed on the opposite side of the obstacle to reduce the potential for down-cycling frame damage. As always, it never hurts to have a spotter check the terrain in front of the lead vehicle before the attempt. Spotters love to spot, so why not use them?

Read More in the Off-Road Driving Technique Series

2009 Range Rover Sport Off-Road

A 2009 Range Rover Sport tackles a off-road trail.



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January 23, 2012

Brandon Jelson

Articles, Buying & Ownership, Off-Road

How To, Off-Road

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