At the risk of wading in here...
I get the idea, but sometimes wonder at the inanity of it. I mean, let's say I have a car with tires at 4/32's on it. I can motor around all day with that, with some decrease in wet traction. I buy a new set of tires, but when they get down to say 6/32's, say I hit something and am forced into getting a matched pair. Suddenly the new tires have to go on the rear, for safety's sake. Somehow 6/32's is dangerously low but 4/32's wasn't.
And I do get the fact that it's about disparate levels of traction... but on a typical front biased FWD car, does it really matter that much?
I just go by the guidelines as they make sense. But I'll fudge them a bit on my own vehicles as I see fit.
I didn't watch the video. IMO we've all just added to Scotty's bottom line here.
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Lately I've been kinda intrigued by how much traction an inside wheel has. I've always thought that, once the body starts to lean over (remember, I drive Toyota's) that the inside wheel is kinda along for the ride. Couple times recently I've taken turns with the inside tires on a bit snow, outside on wet pavement, and I can feel the car slide a bit as a result. I guess all 4 tires really are there for a reason.