There’s a common misconception that grip and traction are the same thing and are interchangeable terms but it’s not quite that simple. Grip, in the context of a car’s contact with the road or other surface, is more to do with the tyres than anything else, while traction is dependent on a more complex product of tyre grip, weight distribution and driven wheels. And it’s the traction that is dramatically enhanced in vehicles with all-wheel drive as long as you have the grip to make use of it. Confused?
A farm tractor has an enormous amount of traction to pull heavy machinery through muddy fields, but try to drive one around a tight corner in the wet and you will very quickly find its limit of grip.
Or to explain it a different way, every single modern car with four wheels also has a brake for each wheel and it’s easy to imagine why. If you need to stop as quickly as possible but the vehicle is only braking two wheels, there are two tyres and all their potential grip that aren’t contributing to deceleration at all. And it’s exactly the same for acceleration too.
Vehicles with two-wheel drive are limited to the amount of power they can transmit to the road through the contact patches of just two tyres. But Subaru’s symmetrical all-wheel drive chassis uses all the available grip from all four tyres. In very simplistic terms, twice the number of driven wheels means double the amount of traction.
And with the maximum amount of traction, the vehicle can accelerate more safely in all circumstances but particularly adverse conditions such as wet and icy weather. That’s why my WRX STI rally car offers such rapid acceleration that’s easy to control even when the track is muddy or covered in loose gravel and sand.
But that same technological advantage isn’t limited to the race track. Subaru’s range of wagons and SUVs are also safer, easier to control and more fun, no matter where you chose to take them.
15 April 2021