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

  • Successful_Try543@feddit.org
    31·
    19 hours ago

    For a road bike, you want to minimize the contact area of the tire with the road so you have very narrow tires and inflated a lot so that they don’t deform much under your weight.

    It’s slightly different:

    • As the top speed of a road bike makes air resistance (drag) an important factor, road bikes use narrow tyres, resulting in a smaller silhouette area than a wide tyre (on a rim of the same diametre) would have.

    • As the rolling resistance increases with the length of the contact area, with the same internal pressure (inflation), i.e. same area of contact, narrow tyres have a higher rolling resistance than wide tyres. Thus, to (over-)compensate and decrease the length of the area of contact the internal pressure of road bike tyres is much larger than of normal, wider tyres.

    As a result, narrow tyres of road bikes have smaller drag and due to over-compensation by inflation an even lower rolling resistance than standard bike tyres.

    Edit: This over-compensation is possible for road bikes, as hard surfaces (asphalt, concrete, pavement) allow a high surface pressure.

    For tyres of dirt bikes not sinking deeply into soft ground (gravel, soil), they need to have a low ground pressure, i.e. a large area of contact and low inflation and thus, cannot be narrow, but have to be wide.