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Trail Savvy: Steep, rocky inclines

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At the Rust De Winter Jamboree (see elsewhere in this issue), steep rocky inclines were the name of the game − and more than a couple of folk came short. There are several fundamentals that are vital in climbing a steep, rocky slope safely: traction, momentum and line choice.

The first and most important aspect of hill climbing is maintaining traction. This is achieved in two ways: line choice and tyre pressure. On rocks, especially, it’s a balancing act between deflating tyres for traction and maintaining clearance. Where clearance is not an issue, you may drop as much as 50% or more below road pressures; but be extra careful on off-camber sections where a soft tyre can roll off a rim.

For added traction, make sure that your differential lock (if fitted) is turned on, especially if there are axle-twisters on the way up. Modern traction-control systems work in most situations as a substitute for lockers, but if you have one (usually on the rear axle, but some vehicles have them on the front axle as well), use it anyway. A diff lock locks the half shafts on the same axle so that both wheels turn at the same rate, irrespective of how much traction they have.

A little more momentum will help when loose rocks pepper the climb. Traction control can be enough on its own when the slope is not too steep.

Of course, without a diff-lock, line choice is even more critical if you are to avoid a cross-axle situation or hang-up. What happens here is that, even with high-range 4WD engaged (the same applies to a permanent-4WD vehicle), when a front wheel and its opposite rear wheel lose traction, you are going nowhere. Traction control will not always figure this out and keep you moving. In this case, it may be necessary to pre-emptively pack rocks into the offending holes, or to use something like a set of MaxTrax recovery tracks to reduce wheelspin.

To make sure that you choose the line of least resistance, it’s best to walk the track before you attempt it, to picture the placement of your wheels. Try to ensure that the sensitive components under your vehicle (like the differentials and oil sump) will not be hitting any rocks – it is imperative that you know where these vulnerable bits are. The trick is to attempt to drive over the rocks with your tyres, as far as possible, instead of letting them hit the underbelly.

To maintain momentum on steep, rocky inclines, select a low gear (usually low-range 1st if the hill contains large, immovable rocks, but possibly 2nd if the rocks are loose) and maintain speed in the torque band. This does not mean that you should rev the nuts out of your vehicle. What you want to do is crawl along at just above idle, so the tyres are unlikely to spin as they may do at higher rpm.

Someone once said that doing the same thing over and over while expecting different results is insanity. With that in mind, if you didn’t make it up the hill the first time, you should try something different – such as reducing pressures some more, picking a different line, or gaining more momentum before the hill.

Pick your line carefully when clambering slowly over big rock steps, and be aware of where the vulnerable low-slung axle housings are on your vehicle.

In the event of stalling

Just as you were taught when you learned to drive a manual, you prevent stalling by putting your foot on the clutch when the vehicle comes to a standstill. On a steep incline, this natural reaction will immediately cause the vehicle to roll backwards. Hitting the brakes with a stalled vehicle will cause them to lock up while it’s rolling backwards, eliminating your ability to steer and potentially resulting in an uncontrolled slide to the bottom.

Generally, an automatic will not stall; but, in the event that forward progress is impossible, remember to engage reverse and go backwards slowly by gently applying brakes and keeping your wheels as straight as possible to reduce the chance of an uncontrolled slide.

Manual vehicles reverse start technique

If stalling is inevitable, allow the vehicle to come to a halt, and engage the brakes without disengaging the clutch. This may seem counterintuitive, but can be vital to a safe descent. Engage reverse with your foot on the brake and the handbrake pulled up. When ready, release the hand brake and then slowly release the foot brake while the vehicle is still in reverse, turning the start key as the brake is released. The vehicle will roll back in a controlled manner under engine compression, although gentle use of the brake may well be needed to stop it accelerating too fast.

The idea behind this technique is to reduce the risk of wheel lock-up when moving in reverse. Unfortunately, most modern vehicles will not allow this reverse-starting technique as they require the clutch to be disengaged fully before allowing the engine to start. In this case, you’ll need to start the engine first, and then slowly release the brake and clutch at the same time.
By Andrew Middleton

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