The Model Y has +89% more volume. Its considerably bigger car with more torque. It's not a good comparison. And even though its 32% heavier and has a ton more torque, its tire wear was 26% greater. You're arguing it goes up by the fourth power, but it wasn't even a 1 for 1 increase on a car with considerably more torque. And besides, their testing shows the tire wear particulates for their comparison gas car as even higher than the Y.
Let me reiterate it again. The Kia is a much smaller car with way less torque. It is a poor comparison from the get-go. Go find a similar sized vehicle with a similar amount of torque. But this study is pretty heavily biased, so they chose their cars accordingly.
But let's continue on and see what it is you're trying to point out.
> Kia has 50% as many emissions
You're now talking about the VOCs table at the bottom. This is a pretty bullshit test overall.
> Large samples from one tyre on each vehicle were also taken and placed in a ‘microchamber’ heated to 20 degrees Celsius, around the temperature of a vehicle certification test, and held at that level for the same duration of the on-road EQUA test – around three-and-a-half hours. The off-gassed VOCs were analysed and quantified, and then scaled up by the relative surface area of the sample to that of all four tyres on the vehicle. The results are shown in the table below.
So, this isn't actually testing the tires under load on the car at all, they're just baking a small piece in the oven and scaling the resulting VOCs to the size of the tires. This test isn't testing the car, its testing the tire. There are no controls over this test. It's just a tire of an unknown age from one car with a part cut out and a tire of an unknown age from another car with a part cut out. The brands and models are pretty different, which could lead to pretty radical results.
If I put brand new tires on that Kia and used some pretty old ones on the Tesla those numbers would look radically different. Even two different models of tires from the same manufacturer could yield vastly different numbers. If you used the exact same model from the exact same manufacturer made at the same time the car with bigger tires would have the worst emissions, which says absolutely nothing about whether that's a tire going on an EV or a sedan with a hybrid engine or a truck with a DEF delete getting 6 MPG. See how that's then a pretty poor test?
Seriously friendo, read the studies you're wanting to use to talk about these things. There's so many absolutely bullshit studies trying to get you to think one way or another. Don't just go "table says 57%, ev bad!"
Now I think I know where you're pulling that fourth power from. You're probably thinking of road wear which does scale like that. But that's road wear, not tire wear, and doesn't result in the same airborne particulate issue here.
And even then, it's small potatoes compared to actual big trucks and busses rolling on the roads.
I was thinking about road wear. I had thought the same equation applied to both tires and the road. Why wouldn't the increases in wear on both increase in the same way? (You seem to know why, so honest question, not snark)
I don't fully know but it is probably something to do with the fact tires are designed to be more malleable and flexible than roads. The tire is also flexing and pushing on an air cushion while the road itself is being pressed against and having to flex with the ground.
Also, almost all the particulate emissions are due to the abrasive nature of the road-tire interface tearing apart the tire. Tires are a cheaper and simpler wear items than roads, something is going to give, so we've decided we'll replace our tires more often than tearing up our roads. Just like if you ever got road rash, the road is going to tear you up far more than you're going to tear the road up. So, while the road forms cracks and what not from its repeated stresses it's not coming apart like dust nearly as much. Don't get me wrong, some small, tiny amount of it does but not nearly as much as the tire.
