That ^2 is a load-bearing exponent which changed my entire perception of safety.

With the oil crisis making it a good time to buy an ebike, I see the same problem popping up on bike forums that I faced when making my original purchase. At least here there’s the option between a Class 2 (32kmh max, usable on paved trails) or a Class 3 (45kmh max, limited to roads). When I bought my first bike I got a Class 3 because I’m getting 40%~ more speed for the same price. I could arrive at my destination 40% faster than I do on my cargo bike.

Assuming a rider+bike weight of 100kg and converting the two to m/s: 8.89m/s, 12.5m/s-

Class 2- 0.5(100)(8.89^2)= 3950 Joules of energy. That’s what you experience when crashing at max speed, the equivalent of falling off the roof of a building with one floor.

Class 3- 0.5​(100)(12.5^2)=7,810 J.

Despite the speed only increasing by 40%~, the kinetic energy you experience in that crash almost doubles. The energy your brakes have to absorb to stop, and with that the stopping distance and wear, almost doubles. Your risk of fatality jumps significantly. You are now jumping off the tallest house in your neighbourhood and that is the level of injury you can expect from the slightest mistake.

If you or anyone you know is tempted to get a hyperbike because it goes much faster than a cargo bike, especially beyond the Class 3 speeds that I don’t even want to think about the injuries from, that impact force needs to be a primary consideration. I am confident that with proper safety gear I have a 90% chance to survive a crash with injuries that won’t last a lifetime. If my cargo bike was Class 3 instead of Class 2, I could not maintain that same level of confidence. It’s such a minor difference when you are looking at generic speed numbers but you will crash and that is the standard you need to prepare for.

Buy a Class 2 and maximise your weight-bearing utility over speed. Slow is smooth and smooth is fast.

  • 7bicycles [he/him]@hexbear.netEnglish
    3·
    6 days ago

    The energy your brakes have to absorb to stop, and with that the stopping distance and wear, almost doubles.

    The stopping distance is mostly a given but otherwise this is mostly a non issue despite getting brought up a lot. Halfway competently maintained V-Brakes which are easy as hell to service will block a tyre which is much more the limiting factor on a bicycle. As in: It’s not that hard to do 45kmh on an acoustic bike and v-brakes are fine for that, even with the bit of weight all the electronics add.

    When I bought my first bike I got a Class 3 because I’m getting 40%~ more speed for the same price. I could arrive at my destination 40% faster than I do on my cargo bike.

    I see the idea but I think that generally never works out in urban areas fairly regardless of mode of transportation bar jogging instead of walking and from my experience in the EU, being able to use paved trails, footpaths and such generally gets you to places much faster compared to more max speed both due to being able to cut across certain infrastructure instead of taking the long way around and the fact that things like bicycle + pedestrian infrastructure doesn’t usually have any sort of meaningful traffic or traffic lights in the way that car infrastructure does