Gear motor and 29r wheel

HI,
Is anyone using gear motor (especialy mxus mx01c 500W) with bike 29" wheel ? and 13S supply ?
What is max speed ? Any problem with temperature ?

I have now ebike with 26", mx01c and 13S5P battery and max speed is 45 km/h.
I want get a little bit more speed and and i wondering to change bike for 29".
Mostly i ride on flat road.

The speed you get will be proportional to the change in wheel size, minus a bit for the power used up by the change in wind resistance at the new speed vs the old.

Since the change in wheel size is only 29 / 26 = 1.12, then the speed change would be about the same, so originalspeed * 1.12 = newspeed.

Then you can look up the speed-to-powerusage charts or calculators like on http://www.kreuzotter.de/english/espeed.htm , and see how much power it takes to do that speed. If you don't have enough power (which you can figure out based on your battery voltage and current capability, and the current capability of the controller), then you won't reach that speed.

If the motor isn't heating up much now, then the increase in heat will again be proportional to the increase in power usage. (though that will be higher than the ratio of the change in wheel size/speed)

If the pedals are geared high enough, then you can add more power that way, and if not y0u cna change to larger front chainring to do it.


Keep in mind that changing the wheel size (and chainring size) to larger ones increases top speed, but it also takes away some of your startup torque, making it harder for the motor (and pedals) to get you started from a stop, by the same ratio the top speed increases.

You might consider 14s as a way to get 2-3 mph more speed, or simply adding more 13s to eliminate sag under load.

Either of those ways to stiffen the battery voltage will help more than a small increase in wheel size.

If you are looking for big increase in speed, its time to bump up the size of the motor, allowing much higher wattage, faster windings, and such. That usually will require a HUGE improvement of your battery, either much larger, or much higher discharge rate, allowing you to run 2000-4000w. This effectively removes your bike from the bike category, and changes it into a home made, usually street illegal, small motorcycle. Fun thing though! 40 mph club, if not more.


But if you just want a more steady 30 mph, then try 14s, and enough of it to not sag much under load. Experiments can be done with an affordable pack wired for 1s, added to the 13s you have. ( 13 plus 1s, in series) That results can help you decide if its worth it to invest in new 14s battery later on, or go for the 40 mph club.

The larger the wheel, the harder it is on the motor. There are good reasons to go 29’’, but I find faster speed is not one of them. Up the volts, is going to do it better than a larger wheel.

When I decided to build a faster commuter, the first mod I did was to go 24’’. Lower bike, lower air drag, lesser leverage on the motor. All benefits to compensate for higher power requirement.

My dirt bike is on 26 with 3.0 tires, that is making 28.5’’ od. It is a good ride on the rough, but a current sucker.

Larger the wheel the hotter everything gets.

My experience w/ higher-speed motors or larger wheels is the controller is most likely to get hot. If the motor is struggling to get up into the higher, more efficient rpm zone, the controller tries to supply as many Amps as it can. I'm talking about climbing mostly.

MadRhino said:

The larger the wheel, the harder it is on the motor. There are good reasons to go 29’’, but I find faster speed is not one of them.

Click to expand...

Unless you are pedaling, then bigger wheels are easier to gear. Pedelecs need conventional wheel sizes to run bicycle speeds with available gearing; it's hard to pedal a small wheel at speed with MTB rings. The best solution considers all factors, not just the motor. Maybe the OP cares about pedaling, maybe he doesn't.

Also, bicycle aerodynamics is overwhelmingly dominated by the rider so lowering the bike a couple inches with a smaller rear wheel is meaningless. Proper bike fit and riding posture are far more important than smaller wheels, even proper clothing would be.

Hi
Thank evryone for reply.

I use my ebike to get to work (about 90%) time - mostly flat road.
I am pedaling all time (i use max 200W electric power).
Now avarage speed is about 30 km/h
I want to incrase avarage speed to 35-40 km/h.

Propably i will change bike to 29" with slim tire (<2 inch) and incrase voltage to 14S with MX01C and 25A controller (sin wave)