21 inch down to 18 inch, good idea??

ebike11

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Hi everyone!
Had a question about motor/wheel performance.

I have a high Kv (3T) qs205 motor in a 21inch wheel but with the tire mounted it is the same height as a 26in bicycle wheel/tire.
Its a little bit too high. I originally read that the bigger the wheel size the more top speed.
Top speed is my main goal after all.

However I was curious how it would perform if I dropped down to a 18 inch wheel ?
The motor would spin faster but Im not sure how top end results would be.
Im using a 28s (117V) pack and high current controller.

The 18 inch would also allow me to put on smoother road tires compared to the more knobby type of a 21 inch tire.

I think the lower stance would look better as well but Im concerned about the performance.

Thoughts are greatly appreciated...thanks!!
 
Same everything except wheel diameter is smaller = less speed but more torque for the 18" vs the 21" which would have more speed and less torque with everything else being equal.
 
calab said:
Same everything except wheel diameter is smaller = less speed but more torque for the 18" vs the 21" which would have more speed and less torque with everything else being equal.

Yes thats also what I have read.
Problem is there arent many nice street smooth tires in 21inch size
Also how would you compensate for the loss in top speed going down to 18inch?
 
ebike11 said:
Also how would you compensate for the loss in top speed going down to 18inch?

The Grin ebike simulator will tell you definitively the top speed and tork out, per amp. Acceleration for each setup too. 18" and 21". In MPH/sec/sec.

28s pack in a 3T QS205? Goddamn how many rpm do you achieve?

Smooth tires do make one hell of a difference int e rolling resistance in my humble opinion.
 
DogDipstick said:
ebike11 said:
Also how would you compensate for the loss in top speed going down to 18inch?

The Grin ebike simulator will tell you definitively the top speed and tork out, per amp. Acceleration for each setup too. 18" and 21". In MPH/sec/sec.

28s pack in a 3T QS205? Goddamn how many rpm do you achieve?

Smooth tires do make one hell of a difference int e rolling resistance in my humble opinion.

Yeah im crazy for speed...lol
I dont see the qs205 in the simulator though
 
Use the CroMo 5004.

https://ebikes.ca/tools/simulator.html?bopen=true&motor=MCRO5004_Sinks&batt=cust_104_0.02_20&cont=cust_200_400_0.03_T&kv=16&hp=0&cont_b=cust_200_400_0.03_T&motor_b=MCRO5004_Sinks&batt_b=cust_104_0.02_20&hp_b=0&kv_b=16&wheel_b=24i&axis=mph

Cromo 5004 is a 50H 9" stator motor ( same as the QS 205). Adjust the kV value under the "advanced options" for your particular motor. Initial tork ( and resultant takeoff acceleration (in mph/sec^2) depends on the amps of your controller really. I


ebike11 said:
DogDipstick said:
ebike11 said:
I dont see the qs205 in the simulator though
 
DogDipstick said:
Use the CroMo 5004.

https://ebikes.ca/tools/simulator.html?bopen=true&motor=MCRO5004_Sinks&batt=cust_104_0.02_20&cont=cust_200_400_0.03_T&kv=16&hp=0&cont_b=cust_200_400_0.03_T&motor_b=MCRO5004_Sinks&batt_b=cust_104_0.02_20&hp_b=0&kv_b=16&wheel_b=24i&axis=mph

Cromo 5004 is a 50H 9" stator motor ( same as the QS 205). Adjust the kV value under the "advanced options" for your particular motor. Initial tork ( and resultant takeoff acceleration (in mph/sec^2) depends on the amps of your controller really. I



not a big difference in top speed to be honest
 

No. It is not.

Better efficiency with the 18" too. 78% vs 75%. You reach a higher RPM. You also use less amps to maintain that (top) speed.

So the range would be better.
 
DogDipstick said:

No. It is not.

Better efficiency with the 18" too. 78% vs 75%. You reach a higher RPM. You also use less amps to maintain that (top) speed.

So the range would be better.

Ok thx for the help...its interesting!
 
DogDipstick said:

No. It is not.

Better efficiency with the 18" too. 78% vs 75%. You reach a higher RPM. You also use less amps to maintain that (top) speed.

So the range would be better.

Hi
I noticed that increasing the battery and phase amps dont increase the top speed..for example, 200A and 400A to 400A and 800A
 
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