The rolling resistance isn’t low but that’s due to the terribly inefficient rubber wheels. Yet to try it on thane, but I do want to some day. With that said, when freespinning the wheel in the air (with the belt on of course), it actually spins a fair amount. Free spin was definitely better without the idler though. With that said, my guess would be that my wheels are so inefficient at least in summer time (35-38C), that it matters a lot more than the resistance of the belt.
Can’t compare to 190KV from experience sadly, as I haven’t tried 190KV motors yet. Can only write down the theory.
Everything below is assuming your ESC can supply any reasonable KV motor with the maximum current the motor can handle without thermal throttling. If your ESC thermal throttles before your motor, then going lower KV is 100% the right choice. Higher KV is harder to run for the ESC at the same performance level.
My take on which KV to take very much depends on riding style, and be ready because this is gonna get complicated. The two main types of energy losses in the motor are copper losses and iron losses. Copper losses are I^2*R, iron losses are much more complicated and increase with the rotational speed of the motor. This means, that when accelerating hard all the time, copper losses are high, so a higher KV motor with the appropriate gearing makes more sense. When the motor is spinning at a relatively high RPM most of the time, but there are mostly mild accelerations, then a lower KV with the appropriate gearing makes more sense.
Copper losses decrease quadratically as KV increases, while iron losses increase quadratically as KV increases.
Basically balancing out these losses doesn’t affect range a whole lot. Yes it affects it, but it’s not super drastic. I imagine maybe 5-10% at most. Where this matters a lot is motor temperature. Keeping the losses balanced ensures that the motor doesn’t overheat as fast.
Now, this paragraph I am not 100% sure about, so someone please correct me if I am wrong. Copper losses are I^2*R. Iron losses can be calculated for a set speed at BEMF voltage * no load current. This is what I am not 100% sure about. Anyways, I found a source for it at least and it makes sense to me https://youtu.be/WqlQJw9YXhE?t=677
But if that’s right, lets take a Maytech closed can 6374 motor, and compare 190KV vs 150KV. Let’s run both at the same current level, for example 70A @12S, I think that was common for these motors. Shout out to @rusins for the data!
190KV:
Copper losses at 70A = 70^2 * 0.014 = 68.6W
Iron losses at full speed 12S = 50.4 * 1.74 = 87.7W
As you can see, spinning the motor at max speed actually generates more heat than pumping 70A through it.
Copper losses at 70A = 70^2 * 0.032 = 156.8W
Iron losses at full speed 12S = 50.4 * 0.95 = 47.9W
Now lets throw the Flipsky 6384 motor in the mix as well, as that’s the most popular motor people seem to run nowadays. Lets look at the losses at 80A 12S. Sadly there is no 190KV data for this motor though
Copper losses at 80A= 80^2 * 0.017 = 108.8W
Iron losses at full speed 12S = 50.4 * 0.88 = 44.4W
This is a rough extrapolation that I made from the Maytech 6374 closed can 150KV and 190KV data. Calculating with 12S 70A. ((Total loss = copper loss + iron loss))
Now, I think the best is to have the copper losses higher than iron losses for street riding with not many hard accelerations but a lot of high speed riding. For this specific motor, somewhere around 140KV does make sense for this style of riding. If you only accelerate hard once, then hold speed at 30A per motor lets say, then a lower KV does make sense. @30A the copper losses are minimal, and with the lower KV, iron losses are minimized.
As for aggressive street riding and high speed hill climbs, I think the sweetspot is around where the iron loss and copper loss intercepts each other, maybe very slightly below. That’s around 170-180KV according to the graph.
As for hard offroading and track racing with a lot of sharp turns, having the iron losses very slightly above the copper losses or at the same level is the way I would like to go when the graph’s main parameters are the max voltage (so max speed) and max current. 180-190KV according to the graph.
PS: These calculations were made with the Maytech 6374 closed can because that’s the most relevant motor with data for at least 2 KV variants. The Flipsky battlehardened series motors, 6374 and 6384 in particular have much lower internal resistances, so with those we can go even slightly lower KV.
Also sorry, this has become way too long, lol