Why are bike tires so narrow and large diameter compared to car tires? What tradeoffs are here exactly? Motorcycle and some ebike tires are more similar to car tires than to bike tires, so i guess it has something to do with braking length at maximum expected speed, and probably also with weight of vehicle, as to not exceed some specified pressure on road. There has to be so many more reasons (weight? air resistance? some other things affecting efficiency or safety? ???)
update: apparently friction involving things that are bendy is monstrously complicated subject, and also there are material limits like maximum allowed shear stress
you sure about it chief? bigger wheels also have larger rotational inertia
Yeah, try riding a folding bike with small wheels, you wobble a lot more.
It’s not about the magnitude of the rotational inertia (which is roughly the same or maybe a bit higher on larger wheels that are probably heavier), it’s about the center of the gyroscopic effect. It’s at a greater height if you have big wheels, and closer to the ground if you have small ones.
A low center of gravity is more stable than a high one.
Gyroscopic effects do exist on bikes but they are not the main source of stability - it’s the fork geometry, which tends to straighten the handlebar
The rotational moment of inertia increases a lot due to the larger diameter, J ~ m r^2. Even if the masses were the same, the relatively heavy tyre and the rim are further away from the wheel hub.
Edit: If we neglect the wheel hub and the spokes, the mass of the tyre and rim scales with the radius, m ~ r, and thus J ~ r^3 .