Hill Ascent and Descent Techniques
Hill Ascent
It is usually best to tackle a hillclimb that’s any sort of challenge in low range. Although you may be able to just reach the top of a hillclimb in 1st high, it doesn't leave you with any lower gears if the need arises. By using say 2nd or 3rd low range instead of 1st high, you have lower gears available if needed. If you run out of gears on a hillclimb, you may have to back down to the bottom of the hill and start again. Most 5-speed gearboxes allow vehicles to travel up to 6Okm/h in low range, so you don't have to be continually swapping between low and high range as you travel between hills.
Diesel vehicles are generally better for hill ascents and descents as they usually have better low rpm torque for climbing the hill and higher engine compression for desending. However, in long sandy hill ascents, where traction is low and a run-up is required, the greater power of petrol engines can be an advantage.
Hill Descent
When descending hills, you should always be in low range and have selected the gear required before descending. You should always avoid braking on downhill sections as you run the risk of locking up your wheels, causing a slide. Engine braking slows the vehicle without causing wheel lockup. However it is better to use the brakes than allow the vehicle to 'run away' and pick up speed. Always apply the brakes gently, rather than applying them abruptly and risking a wheel lockup.
Often hills get steeper the further you go down, so its best to be in 1st low from the beginning rather than having to try and change gear halfway down. When changing down a gear while descending, it is best to be feathering the brakes as you depress the clutch, as otherwise the vehicle freewheels while the clutch is depressed and picks up speed. It is far better to be in too low a gear and travel down slowly rather than be in too high a gear and have a potentially dangerous situation arise.
Hill Stall Recovery
A very common occurrence on hill climbs is the stalling of the vehicle when the hill becomes too steep. When this occurs, you will be left in gear with the engine switched on but stalled. To recover from this situation you should perform a Hill Stall Recovery, rather than just fire up the engine. This is accomplished by:
- Switch the (stalled) engine off and place your foot firmly on the brake.
- Depress the clutch and select reverse gear in low range.
- Take your foot off the clutch then slowly take your foot off the brake. The vehicle is now in reverse gear with the stalled engine stopping it from rolling down the hill.
- After checking the track behind is clear, start the engine and keep your feet off all pedals.
- The starter motor will start to drive the vehicle backwards as the engine begins to fire.
This will result in a smooth downhill progression while starting the engine and ensuring you have been in gear at all times. If you simply start the engine and then select reverse gear, it will result in a fast jerky takeoff and being out of gear during some stage of the takeoff.
The Hill Stall Recovery does not apply to automatic vehicles as they should never stall, just lose forward drive when the hill becomes too steep for the gear its in. When this occurs, simply place your foot on the brake while restarting the engine, select the appropriate gear and gently take your foot off the brake.
Vehicle Rollover
Hills should always be tackled straight up or down and sideway slopes avoided like the plague. A vehicle has to be at an extreme angle for it to roll head to tail, whereas a sideways roll can occur at much more modest angles. The way your luggage is packed has a pronounced affect on the angle a vehicle will roll sideways. You should avoid placing containers of extra fuel and water on the roof of your vehicle, as this will significantly decrease the angle at which a rollover is possible. This occurs because the extra weight on the top of a vehicle increases the 'centre of gravity'. Heavy gear should always be packed low inside the vehicle while only lightweight gear should be placed on roof racks.
The type of terrain will also affect the sideways rollover angle. In sand, mud or other soft terrain the weight transfer to the downhill wheels will cause them to sink, increasing the actual slope angle. So what may appear an acceptable angle on firm terrain may result in a rollover on soft terrain.