Tech Torque
POWER, torque, weight, gearing, ground clearance, wheel travel, tyres and electronic traction control are just some of the things that make or break a 4x4. But what attributes are more important than others? Can power always overcome weight? Can traction control always make good on poor wheel travel? And can you make up with a lack of torque through low gearing?
Rating what counts when it comes to a 4x4’s ability is difficult, but the list, in roughly descending order, would look something like this:
GROUND CLEARANCE
THIS is the biggie. Without decent ground clearance, you really have nothing going for a 4x4 in any sort of off-road environment. Regardless of whether you’re on sand, in mud, or on rocky and rough terrain, you aren’t going anywhere without decent ground clearance. And the softer the sand, the deeper the mud, or the more rocky and broken the ground, the more that clearance becomes invaluable. With more clearance you can also carry more momentum without risking damage to the vehicle’s vitals or body and body panels, and there’s less need for extra-low gearing. Too much ground clearance is only a problem when the vehicle sits up that high that side-slope angle and roll-over stability is unduly compromised.
WEIGHT
LESS weight means you less readily sink into any soft surface – sand, mud, or whatever. What’s more, it requires less of just about everything else – power, gear reduction, traction, etc. – to move a lighter vehicle up a hill than it does a heavier vehicle.
WHEEL TRAVEL
ALONG with ground clearance and less weight, wheel travel makes up the ‘holy trinity’ of 4x4 attributes. Long wheel travel allows you to traverse broken ground more easily, with less reliance on diff locks or traction control. As with extra ground clearance, it also allows you to carry more momentum across any surface, so there’s less chance of bogging in soft sand or mud.
TYRES
YOU don’t get far off-road without suitable tyres; although, it’s much more than just tread pattern at play here. In broad terms, the important things are tyre construction (Light Truck is more robust than Passenger), sidewall height (the higher the better, for superior damage resistance and air-down advantage) and speed rating (the lower the better as high-speed tyres are lightly built, even if this sounds contradictory). Tread pattern is vital when it gets muddy, but not as important when you’re not in mud.
TORQUE
DECENT torque output is the only way to get the usable off-idle and low-rpm driveability and stall resistance you need off-road. Extra low gearing can overcome a low torque output, but only to a certain degree.
DIFF LOCKS
WHEN a 4x4 runs out of wheel travel and loses solid contact with the ground, you can’t go past a locking differential. Those that lock automatically (generally called electronic or ‘e’ lockers) are much more useful and convenient than driverengaged lockers.
Lockers are generally found on the rear axle; although, full-time 4x4s need locking centre diffs (either auto or manual), while a handful of 4x4s (70 Series, Wrangler Rubicon and Mercedes G-wagen) have front lockers as well. One note of caution here, some driverswitched rear lockers on current 4x4s cancel the traction control on both axles, so they don’t necessarily deliver on their promise.
TRACTION CONTROL
TRACTION control was once a poor man’s diff lock, but recent examples – second and third generation traction control systems – are becoming very effective. Traction control is part of the answer, but not the full answer, to lack of wheel travel in modern car-like 4x4s.
POWER
YOU don’t need heaps of power when off-road – at least away from soft sand, and only then when you have a heavy 4x4. As above, torque is what’s needed off-road, while power is a more critical on-road attribute.
DUAL-RANGE GEARING
THIS is a simple, cheap and effective way to get low gearing and still use an otherwise standard gearbox. However, dual-range gearing isn’t essential as long as you have a sufficiently low first gear, which is something made possible when you have a gearbox with a stack of ratios such as with modern eight- and nine-speed automatics. On the other hand, with automatics, a torque convertor with a high-stall ratio can be a solution and help overcome the need for dual-range gearing.