Quote:
Originally Posted by whoosh
LOL, this is a total game of semantics...
Scenario:
6" of new snow falls on a hilly driveway. 4x4 SUV is left in RWD configuration, and fails to get up driveway. Driver shifts the vehicle into 4WD, and is able to make it up the driveway. Same tires, same conditions, but the 4WD mode makes the difference between being stuck and getting going. I call that traction - I'd be interested to see what term you have for that if it's not traction.
|
OK. This topic was concluded a while back, but with your thought-out scenario, let's pick it up again.
(Those who are tired of this topic might wish to stop reading now and find a different thread!) If I hold 4WD as a constant and vary the kind of tires on the front wheels, the potentially beneficial effect of engaging 4WD will change accordingly. Therefore, 4WD is not the ultimate source of the traction. It is determined by the tires, because the traction occurs between the tire and the road surface, not in the differentials nor axles of 4WD hardware. All 4WD does is enable two more tires to have motive power, and
if the tires are of the proper type, gain traction with the ground underneath. Bald PSS up front would have essentially no helpful effect, exaggerating the scenario to point out the logic.
Depending on your age, you may recall the "Necessary but insufficient" type of questions in the old SAT. For improved overall vehicle traction vs RWD, 4WD is necessary in the vehicle but is insufficient without proper tires, as with tires with low-to-no traction on a low mu surface, there would be no beneficial effect of 4WD. Car mags have proven more than once that 4WD/all seasons cannot keep up with RWD on winters. So, while 4WD can help in the situation you describe, it helps not by adding traction of its own, but by enabling the two additional tires which the 4WD powers to gain the helpful extra traction.
This is a distinction with a difference and not relegated to mere semantics. The reason this is important to understand is for drivers to realize they need to pay attention to tire selection and not just rely on having 4WD . Far too many do not and wind up with their all-seasons facing skyward and the roof in the snow. Claiming 4WD,
per se, "adds traction" just reinforces the misunderstanding. The caveat about tires should always be included.