USABMX Track # 862

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BMX RIDER BIKE SIZING CHART
RIDER HEIGHT
FRAME SIZE
TOP TUBE LENGTH
STEM LENGTH
BAR RISE
CRANK LENGTH
4'0" & under Micro-Mini 15"-16" Mini 2"-2.5" 135-140mm
4'6" & under Mini 16"-17" Mini-Mini XL 2"-3.5" 140-155mm
4'4"-4'10" Junior 17"-18.5" Mini XL-Pro 3"-5" 155-170mm
4'8"-5'4" Expert 18.5"-19.5" Pro 5"-7" 165-175mm
5'4"-5'10" Pro 20"-20.5" Pro-Pro XL 7"-8" 175-180mm
5'10" & over Pro XL or Pro XXL 20.5" & over Pro XL-Pro XXL 7"-8" 175-185mm

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Gear Inch/Actual Rollout Calculator

Enter the values in the three boxes above and press the Calculate the Gear Inches button.
Front Gear Size (teeth):
Freewheel Size (teeth):

Wheel Height in Inches:

(From Ground to Top of Tire)

20 x 1.75 = 19.5"    20 x 1.50 = 19.0"    20 x 1.375 = 20.5"    20 x 1.125 = 20.0"

24 x 1.75 = 23.5"    24 x 1.500 = 23.0"  

these sizes are for general reference - actual tire diameter varies from brand to brand

 

The Gear Inch Calculation Is ....
Distance traveled in one full crank revolution    ...measured in inches
If you used a   chainring, you would travel inches.
If you used a   chainring, you would travel inches.
If you used a freewheel, you would travel inches.
If you used a freewheel, you would travel inches.

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For Exact Gear Measurement... Divide Front Gear by Rear Gear and Multiply by Tire Diameter

Example: 44/16 = 2.75 x 19.5 = 53.625 gear inches (20x1.75 tire)

 

these charts are for general reference - actual tire diameter varies from brand to brand

 

20" X 1.75" GEAR CHART (19.5" tire diameter) = any size rider
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 14 47.4 48.7 50.2 51.6 53.0 54.4 55.7 57.1 58.5 59.9 61.9 62.7 64.1
Freewheel 15 44.2 45.5 46.8 48.1 49.4 50.7 52.0 53.3 54.6 55.9 57.2 58.5 59.8
Freewheel 16 41.4 42.7 43.9 45.1 46.3 47.5 48.8 50.0 51.2 52.4 53.6 54.9 56.1

 

20" X 1.50" GEAR CHART (19" tire diameter) = riders under 150lbs
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 14 46.8 48.1 49.5 50.9 52.3 53.6 55.0 56.4 57.5 59.1 60.5 61.8 63.2
Freewheel 15 43.6 44.9 46.2 47.4 48.8 50.1 51.3 52.8 53.9 55.2 56.5 57.7 59.1
Freewheel 16 40.9 42.1 43.3 44.5 45.7 46.9 48.1 49.3 50.5 51.7 52.9 54.1 55.3

 

20" X 1.375"(1 3/8) GEAR CHART (20.5) = riders under 120lbs
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 14 49.7 51.2 52.7 54.2 55.7 57.1 58.7 60.2 61.6        
Freewheel 15 46.4 47.8 49.0 50.4 51.6 53.2 54.6 56.0 57.4 58.7      
Freewheel 16   44.8 45.9 47.3 48.6 49.9 51.2 52.5 53.8 55.2 56.4 57.8 60.4

 

20" X 1.125"(1 1/8) GEAR CHART (20" tire diameter ) = riders under 80lbs
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 14 48.6 50.0 51.4 52.8 54.3 55.7 57.1 58.6 60.0 61.4 62.8 64.3 65.7
Freewheel 15 45.3 46.7 48.0 49.3 50.7 52.0 53.3 54.7 56.0 57.3 58.7 60.0 61.3
Freewheel 16 42.5 43.8 45.0 46.2 47.5 48.7 50.0 51.2 52.5 53.7 55.0 56.2 57.5

 

24" X 1.75" GEAR CHART (23.5" tire diameter) = any size rider
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 15 53.2 54.8 56.4 58.0 59.5 61.1 62.6            
Freewheel 16 49.9 51.4 52.8 54.3 55.8 57.3 58.5 60.2 61.6 63.1      
Freewheel 17 47.0 48.4 49.7 51.1 52.5 54.0 55.3 56.6 58.2 59.4 60.8 62.2  
Freewheel 18       48.3 49.6 50.9 52.2 53.5 54.8 56.1 57.4 58.7 60.0

 

24" X 1.50" GEAR CHART (23" tire diameter) = riders under 150lbs
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 15 52.1 53.7 55.2 56.7 58.2 59.8 61.3 62.8 64.4 65.9 67.4 69.0 70.6
Freewheel 16 48.4 50.3 51.8 53.2 54.6 56.0 57.5 58.9 60.3 61.8 63.2 64.6 66.2
Freewheel 17 46.0 47.3 48.7 50.0 51.4 52.8 54.1 55.5 56.8 58.8 59.5 60.8 62.3
Freewheel 18 43.4 44.7 46.0 47.2 48.5 49.8 51.1 52.4 53.7 54.9 56.2 57.5 58.9

 

website by troy@ApexBMX.com