Originally Posted by
HTupolev
Due to the quadratic term, that's not how the math shakes out. 20->40 is not the same as 0->20. For the static portion, it's not...
.5*85*(5.55556^2)
...but rather...
.5*85*(11.1111^2 - 5.55556^2)
...which is 3935J.
Similarly, the rotating KE difference is about 278J, or 231J for the 2.5kg example.
Good catch, I had forgotten that my spreadsheet was starting with u=0
So those figures are actually for 0-20 kph
20-40 kph in 3 seconds requires around 1400W with a 15W saving for 0.5kg rim mass. Time saving is the same at 0.03 sec.
Either way it's not a lot for a seriously major acceleration and very large rim mass saving.