Can someone explain this?
In: Physics
It’s all compromises. General road tires on a car (and a normal bike) are a compromise of minimal resistance, compound, weight, and reliability.
On a car, the more you want to get power down, the wider the tire gets (and more slick the tread), as it’s very easy to overcome the amount of power to downforce you have, and spin the tires. Conversely the steering wheels are a compromise between the amount of grip you want, while not making slow speed driving a process of grinding away large portions of tire on the ground, but not having the tires so wide that you have more grip than you really need. Most cars this means the same or almost the same width tires on front and back (assuming rear wheel drive). You also tend to have body panels covering most of the tire, so the thickness having an impact on aerodynamics is *less* of an issue.
On a bike, the more grip you want the wider the tire gets, so you get into BMX and mountain bikes, and being more capable in more weather conditions on the road. On the other side the faster you go the thinner you make the tires, to reduce the impact of that road drag, because you generally aren’t going to have enough power to weight, to spin the tires. This is also going to reduce your grip, meaning you’re more likely to slide off in bad road conditions, and less able to turn using purely the handle bars, but this is less of an issue on a bike since a large portion of your steering is done by leaning. This is also going to reduce weight, reduce aerodynamic drag (being thinner), but also reduce braking power (more likely to skid even in perfect conditions).
The ultimate TL;DR is that the power:weight(/downforce) on a bike will very rarely be enough to spin the tires, where on a car that is a very common issue with even mid and some lower performance cars.
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