Brake / Throttle Modulation

Getting stuck is something we know is likely to happen when traveling off-road. Sometimes we choose a line that is not favorable, our electronic traction aids are not engaged, we forget to put the vehicle in 4-wheel drive, the terrain, lack of clearance, and the list goes on.

One reason for the lack of traction is the open differential working against us off-road. Essential for allowing each wheel or front and rear axles to rotate at different speeds, a differential provides the necessary different wheel rotation when turning or when road conditions vary. However, the very design that allows for smooth cornering on paved roads can become a liability off-road. In situations where one wheel loses traction, the standard differential sends the same torque to each wheel. When one of those wheels demands less torque to rotate – like when it is in the air or slipping on muddy ground – the other wheel will get the same reduced amount of torque. However, that reduced amount of torque is insufficient to move the vehicle forward and leaving you stuck.

To provide equal torque to both wheels on an axle you might utilize a locking differential. There are many types of locking differentials, and they are useful to get both wheels to assist. The best time to use a locker to help increase traction is when travelling uphill or downhill in a straight line. If your vehicle is at any angle, the locker can make your scenario worse causing your vehicle to move off-track. Lockers are useful and have their place.

An alternative technique, brake throttle modulation can assist in circumstances where the vehicle loses traction due to cross-axle orientation, loss of traction to one wheel on the front or rear axle, or the vehicle needs to bump over an obstacle. This is counter intuitive to everything you have learned about driving on pavement. When driving on pavement it is strongly recommended to use one foot for operating the gas and the brake. By taking your foot off the gas and then applying the brake you can reduce speed and brake more quickly.

Additionally, brake throttle modulation is part of mechanical sympathy. This is true in part but can and will overheat the torque converter in an automatic when overused. Brake throttle modulation should only be used when necessary. When driving off-road we must control the speed into obstacles, rocks, and reduce as much damage and abuse to the vehicle to avoid mechanical failure. By understanding how the equipment works and how to best utilize it we can maintain the vehicle’s ability to get us to and from our pre-determined destinations.

Brake throttle modulation is completed by placing both feet at the pedals. One foot controls the accelerator and the other foot controls the brake. The foot that controls the accelerator should typically hold the engine rpm just above torque converter lock up in an automatic vehicle, this would usually be around 1200 – 1500 rpm. The foot that is on the brake adjusts the amount of braking applied as necessary. With practice one will know how much gas and how much brake should be applied to get through a particular obstacle. However, it is best to only adjust braking load while trying as far as possible to keep engine rpm constant with the accelerator.

Imagine you are approaching a cross axle portion of a trail. As you approach you will apply brake to provide resistance to the wheels. The accelerator is applied as you drive through the brakes. The brake resistance applied to the wheels will require more torque to be sent to the wheels. The more brake pressure applied; the more torque given to the wheels The torque is sometimes enough to get the tire that would have not turned to turn and get you through an obstacle. Another application is approaching a step that you would climb up. Approaching the obstacle, you would apply brake to control the ascent of the vehicle. Controlling the braking up will assist with torque application.

 

Utilizing this technique is a skill and takes practice to become proficient. Once you have perfected this skill your vehicle will perform better off road, be less prone to damage, and the ride will be more comfortable while traveling on the trail. Vehicle manufacturers have different ways to assist with traction with electronic traction control systems utilizing ABS and the application of brake throttle modulation may interrupt those features. Understanding your features strengths and weaknesses are important skills to learn. Seek quality off-road driver’s training from an International 4-wheel Drive Trainer’s Association trainer.

We invite you to come train with us.