CHANDLER
BMX RACING
 

BIKE-TECH

This page will be dedicated to helping parents & racers in their quest for the best information on bikes and gear...

HOW DO I KNOW WHAT SIZE BIKE I SHOULD RIDE?
Well, Here is a Little HELP...

 

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 = 21.0"    20 x 1.125 = 20.0"

24 x 1.75 = 23.5"    24 x 1.50 = 23.0"    24 x 1.375 = 24.0"    24 x 1.125 = 22.6"

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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BMX Gear Charts

 

Most Pro BMX'rs Run Approximately 54 gear inches

44/16 gear ratio with 20x1.75 tire is the most commonly used combination in BMX

 

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)

 

click here to link to more in depth gear charts on crupi's website

 

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 (21" tire diameter) = riders under 120lbs
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 14 51.0 52.5 54.0 55.5 57.0 58.5 60.0 61.5 63.0 64.5 66.0 67.5 69.0
Freewheel 15 47.6 49.0 50.4 51.6 53.2 54.6 56.0 57.4 58.8 60.2 61.6 63.0 64.4
Freewheel 16 44.6 45.9 47.3 48.6 49.9 51.2 52.5 53.9 55.2 56.5 57.8 59.1 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

 

24" X 1.375" (1 3/8") GEAR CHART (24" tire diameter) = riders under 120lbs
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 15 54.4 56.0 57.6 59.3 60.7 62.4 64.1 65.5 67.2 68.9 71.3 72.0 73.7
Freewheel 16 51.1 52.5 54.0 55.5 57.0 58.5 60.0 61.4 63.1 64.5 66.0 67.4 69.1
Freewheel 17 48.0 49.4 50.8 52.2 53.6 55.1 56.5 57.9 59.3 60.7 62.1 63.3 65.0
Freewheel 18 45.3 46.5 48.0 49.4 50.7 52.0 53.3 54.7 56.0 57.3 58.5 60.0 61.4

 

24" X 1.125" (1 1/8") GEAR CHART (22.6" tire diameter) = riders under 80lbs
CHAIN WHEELS
34
35
36
37
38
39
40
41
42
43
44
45
46
Freewheel 15 51.3 52.8 54.3 55.8 57.3 58.8 60.3 61.8 63.3 64.9 66.3 67.9 69.4
Freewheel 16 48.1 49.5 50.9 52.3 53.7 55.1 56.6 57.9 59.5 60.8 62.2 63.9 65.1
Freewheel 17 45.2 46.6 47.9 49.3 50.6 51.9 53.2 54.6 55.9 57.2 58.6 59.9 61.3
Freewheel 18 42.7 43.9 45.2 46.6 47.7 49.1 50.3 51.5 52.8 54.0 55.3 56.6 57.9

 

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