Quote:
Originally Posted by bjcarls
On the three wheel - to me it looks like it moves forward because it starts to grip the side of the roller base. Idk...or really care.
X7 did it much faster and smoother which just confuses me. I’d need to know the software and mechanical differences.
|
You're absolutely right in your assessment, and that's why "roller" traction test results are questionable at best.
The vehicle always ends up moving forward because of momentum, not traction.
In the real world, this does happen in something like snow or mud as tires eventually gain traction, but that's not the point of this test.
The point of these tests are to highlight the efficiency of an awd system, and its strengths and weaknesses.
In theory, in a roller test, you should be able to apply light throttle, continuously, and the car should gain traction. Time and time again, as in this video, the driver floors the accelerator, which then causes a tire to "catch" the roller, in conjunction with forward weight and momentum.
The proper way to do these tests is the opposite of what's being shown....you provide artificial traction, and real slippage (think wet ice), not artificial slippage. This way, you remove the infinite variables involved in creating a zero traction (artificial) environment, especially through something like a mechanical roller. On the other hand, a surface that provides grip has few, if any variables, assuming that the surface provides traction.
Here, you're simply watching a roller test, which could have a hundred different outcomes depending on the rollers used, and the way the vehicle is being driven.