When contemplating a non-hub motor, the maximum motor RPM target and gearing equations can get complex. By selecting the lowest top speed that can satisfy your performance needs, torque will be maximized across the resulting rpm band.
From reading here, most builders have settled on wheel diameter and top speed desired when they begin pondering motor Kv selection, voltage to be used, and gear-down options. I have compiled this chart to make the process a little easier.
This link is a pedal cadence calculator (thanks, Drunkskunk), but if the sprocket and chainring tooth-count numbers entered are the same (1:1) then the pedal-cadence will be the same as the rear-wheel rpm.
http://www.machars.net/bikecalc.htm
If you want to use a tire with an odd outside diameter (such as a fat moped tire on a 20-inch bicycle wheel, which would typically be 22-inches), you go to the tire selection and click on “other", then enter a number of the tire outside diameter into the next square in inches (decimals allowed, 1/4-inch is 0.25).
For instance, if using a custom tire with an outside diameter of 60-centimeters, you would use an online conversion calculator, then enter the result of 23.62 (inches) into the cadence calculator
Other---> wheel (using 1:1 gears) to find the top-speed/rpm result. Suggestions welcome...
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Here's another method:
(10 mph x 5280 feet/mile) / 60 min per hr = 880 feet per min, so...
10-MPH = 880 feet per minute
The diameter of the wheel is X inches. In one revolution, it travels a distance equal to the circumference of the wheel, which is Pi times the diameter:
(X inches x 3.14159) / 12 inches = Y feet (if X is 26-inches, Y = 6.81 feet)
Then we just calculate the number of revolutions needed to travel 880 feet:
(880 feet/min) / (Y feet/rev) = Z RPM (880 / 6.81 = 129.3 RPMs for 10-MPH)...which is equal to 12.9 for 1-MPH
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http://www.onlineconversion.com/
1 mph = 1.609 kph
1 kph = 0.621 mph
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29 inch tire
11.6 RPM per one-MPH
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27.5 inch tire
12.2 RPM per one-MPH
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26-inch tire
1 mph = 12.93 rpm
1 mph = 1.609 kph
1 kph = 8.10 rpm
MPH (km/h) = RPM
01__(1.61)___12.9
02__(3.22)___25.9
03__(4.83)___38.8
04__(6.44)___51.7
05__(8.05)___64.7
06__(9.65)___77.6
07__(11.26)__90.5
08__(12.87)__103.4
09__(14.48)__116.4
10__(16.09)__129.3
11___(18)___142
12___(19)___155
13___(21)___168
14___(23)___181
15___(24)___194
16___(26)___207
17___(27)___220
18___(29)___233
19___(31)___246
20___(32)___259
21___(34)___272
22___(35)___285
23___(37)___297
24___(39)___310
25___(40)___323
26___(42)___336
27___(43)___349
28___(45)___362
29___(47)___375
30___(48)___388
31___(50)___401
32___(51)___414
33___(53)___427
34___(55)___440
35___(56)___453
36___(58)___465
37___(60)___478
38___(61)___491
39___(63)___504
40___(64)___517
MPH (km/h) = RPM
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24-inch tire
1 mph = 14.00 rpm
1 mph = 1.609 km/h
1 kph = 8.80 rpm
MPH___(km/h)___RPM
01__(1.61)___14
02__(3.22)___28
03__(4.83)___42
04__(6.44)___56
05__(8.05)___70
06__(9.65)___84
07__(11.26)__98
08__(12.87)__112
09__(14.48)__126
10__(16.09)__140
11___(18)___154
12___(19)___168
13___(21)___182
14___(23)___196
15___(24)___210
16___(26)___224
17___(27)___238
18___(29)___252
19___(31)___266
20___(32)___280
21___(34)___294
22___(35)___308
23___(37)___322
24___(39)___336
25___(40)___350
26___(42)___364
27___(43)___378
28___(45)___392
29___(47)___406
30___(48)___420
31___(50)___434
32___(51)___448
33___(53)___462
34___(55)___476
35___(56)___490
36___(58)___504
37___(60)___518
38___(61)___532
39___(63)___546
40___(64)___560
MPH (km/h) = RPM
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22 inch diameter tire (Pirelli ML75 moped tire on a 20-inch rim)
15.3 RPM per one-MPH
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20-inch tire
1 mph = 16.81 rpm
1 kph = 10.50 rpm
10 mph (16 kph) = 168 rpm
11 (18) = 185
12 (19) = 202
13 (21) = 219
14 (23) = 235
15 (24) = 252
16 (26) = 269
17 (27) = 286
18 (29) = 303
19 (31) = 319
20 (32) = 336
21 (34) = 353
22 (35) = 370
23 (37) = 387
24 (39) = 403
25 (40) = 420
26 (42) = 437
27 (43) = 454
28 (45) = 471
29 (47) = 488
30 (48) = 504
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16 inch tire
21 RPM per one-MPH
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