Quote:
Originally Posted by bluesman
Simple - putting those sandbags all the way at the back of the car increases its polar moment of inertia, which means it's less sensitive to steering input, it's less prone to spin, and spins will be slower. But if the rear does break loose, it'll be harder to stop the skid until the rear is in front. So when the rear breaks loose, the rear will end up leading the car (the backwards dart analogy) unless stopped by a snowbank or guardrail in mid-skid. It's the skater with his arms held wide apart.
If you put those sandbags as far forward as you can (e.g. against the back of the raised rear seat), you reduce the car's polar moment of inertia. This makes it more sensitive to steering input, more prone to spin, more likely to keep spinning, and more likely to spin faster. It's the skater with her arms tucked in at her sides.
Shorter wheelbases make PMI a more critical factor in handling. So shorter lighter cars like ours can be affected by even 50 pounds of sand put in the wrong place during winter driving.
Weight at ends of car + loose rear end = slower spin to 180 or less. Weight toward center of car + loose rear end = fast 360s.
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Isn't there something to be said for the weight on the rear axle applying more pressure to the tire's contact patch? If there's more weight, it effectively acts as a larger fin on a dart. I understand sliding on ice is an entirely different scenario, but as a slide begins in snow the tires do have some directional authority as they roll, it's not a complete loss of grip.