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Comment by Aurornis | Hacker News Reader

It's even worse than that. Rain performance and rolling resistance are conflicting goals. A good rain tire will need more voids to channel the water, but adding a lot of voids increases rolling resistance.

California is a large market. Tire manufacturers probably won't make many California-specific tires. They're going to try to adjust their tires to meet the California guidelines. The most populous areas of California aren't known for demanding a lot of rain tires.

So if you live somewhere with a lot of rain, your tire choices are about to get worse to appease regulations in a state you don't live in.

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It's hard to imagine median driver performance is SoCal being any worse in heavy rain than it already is.

I'm not sure the tires matter all that much if you don't alter your driving at all.

I'm not sure about your imagination. If people had worse tires then it would be even more difficult to go straight from the far left lane to the offramp 20 above the flow of traffic. /s

Off-ramp? They have trouble going in a straight line.

This is what I always thought. But I have Pirelli Cinturato SF3 tires now. All season. Excellent stiffness and feel. Great handling in the wet. Virtually silent up to 80-90km/h and as efficient as the Michelin summer tires and more efficient than the continental winter tires I had.

So apparently, design and compound can cater for a lot.

Unfortunately, snow performance on my front drive car is worse than my XC90 has in AWD mode with summer tires. (

Design and compound matters a lot, but it's still a tradeoff.

The easiest way to increase rolling resistance is to reduce the tread depth. Less deformation of the rubber leads to less rolling resistance.

So to improve rolling resistance, the designers can reduce tread depth and move to a harder compound, which trades off grip.

Modern tires are good, but everything is tradeoffs.

Of course it is trade-offs. But not all trade offs are linear on the same axis and conditions. For example, changing the compound to make it a bit harder may increase the longevity of the tire significantly in moderate climates at only a limited decrease in grip. And maybe even improved cornering.

Tire manufacturers tend to have different compounds for Europe (focused on lower rolling resistance) and North America (focused on traction and a wider range of working temperatures). I'd guess that California will now simply get the EU variants instead of the NA variants.

From what I remember European tired were often outperforming American tires in stopping performance and other metrics. So not sure that's true.

EU tires focus on low rolling resistance and low breaking distance (due to environmental and safety regulations), NA tires focus on durability (became people drive a lot more) and suitability for a wide range of temperatures (became of the climate).

I would assume US tires also focus more on milage too. Europeans don't drive as far and you don't really want a bunch of old aged tires still driving around even if they got the tread.

Precisely because NA drivers drive a lot more, NA compounds are more focused on durability rather than increasing car mileage. EU drivers are alright with less durable compounds because rubber gets cooked after a few years and would have to be replaced anyway.

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