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In BMX racing, your gear ratio is very important. It's important that you know how to change your ratio and when. Different track conditions, wind factors, ect. may require a different gear ratio. You need to know a little about gears and gear ratios before making gear changes yourself. A gear ratio is the number of times your rear sprocket turns for every full rotation of your front sprocket.

Experiment and don't be afraid to try different gear ratios. You'll see what works best for you.



Since you can't always have a gear chart by your side. It's important to know how to calulate your gear ratio yourself. All you do is take the number of teeth on your chainring and divide it by the number of teeth on your freewheel, that gives you your gear ratio. For example, if your front sprocket is a 45 tooth, and your rear sprocket is a 16 tooth, then your gear ratio would be 2.8125 (45 divided by 16 = 2.8125). You then take that number (in this case 2.8125) and multiply it by 20 (the diameter of a BMX wheel). 2.8125 x 20 = 56.25 (the gear size). You can apply this simple formula to cruisers (BMX bikes with 24" wheels) by multiplying the gear ratio by 24 instead of 20.

If your gear size is large 58 or greater, you will go faster, but take off slower. It will take longer to reach top speed. Snapping out of the gate, going uphill, powering out of turns, etc. will be harder with a high gear. On the other hand, a low gear size of 55 or less will result in a better start, but lower overall speed.

How do I know what size gears I should ride?

Use the chart below to help you decide what size gears you should be riding. 

The Top row of numbers is the number of teeth on your chain ring.  The Rear "XX" column is the number of teeth on your rear sprocket.  Where the two numbers intersect is your gear ratio for the gears selected. 

What do these numbers mean?  Well for every complete revolution of your cranks you go that many inches.  For instance if you have a Rear Sprocket of 16 and a Front Sprocket of 43 and the size of your wheels is 20" X 1.75" then you would get 52.4, meaning you traveled 52.4 inches every time your cranks go all the way around.

Gear Chart for 20" X 1.50" wheels
Chainwheel 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Rear 14 46.8 48.1 49.5 50.9 52.3 53.6 55.5 56.4 57.5 59.1 60.5 61.8 63.2 64.6 66.0
Rear 15 43.6 44.9 46.2 47.4 48.8 50.1 51.3 52.6 53.9 55.2 56.5 57.7 59.1 60.2 61.6
Rear 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 56.5 57.7
Rear 17 38.5 39.6 40.8 41.9 43.1 44.1 45.2 46.4 47.5 48.7 49.8 51.0 52.2 53.1 54.3
Rear 18 36.4 37.4 38.5 39.6 40.6 41.7 42.8 43.9 44.9 46.0 47.0 48.1 49.2 50.3 51.3


Gear Chart for 20" X 1.75" wheels
Chainwheel 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Rear 14 47.4 48.7 50.2 51.6 53.0 54.4 55.7 57.1 58.5 59.9 61.3 62.7 64.1 65.5 66.9
Rear 15 44.3 45.4 46.8 48.1 49.4 50.7 52.0 53.3 54.6 55.9 57.2 58.5 59.8 61.1 62.4
Rear 16 41.5 42.7 43.9 45.1 46.3 47.5 48.8 50.0 51.2 52.4 53.7 54.9 56.1 57.3 58.5
Rear 17 39.0 40.2 41.3 42.5 43.6 44.7 45.9 47.0 48.2 49.4 50.5 51.7 52.8 53.9 55.1
Rear 18 36.8 37.8 39.0 40.1 41.2 42.3 43.3 44.4 45.5 46.6 47.7 48.8 49.9 51.0 52.0


Gear Chart for 20" X 1 1/8" wheels
Chainwheel 34 35 36 37 38 39  40 41 42 43 44 45 46 47 48
Rear 14 48.6 50.0 51.4 52.8 54.3 55.7 57.7 58.6 60.0 61.4 62.8 64.3 65.7 67.1 68.6
Rear 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 62.7 64.0
Rear 16 42.5 43.8 45.5 46.2 47.5 48.7 50.0 51.2 52.5 53.7 55.0 56.2 57.5 58.7 60.0
Rear 17 40.0 41.2 42.3 43.5 44.7 45.9 47.0 48.2 49.4 50.6 51.8 52.9 54.1 55.3 56.5
Rear 18  37.7 38.8 40.0 41.1 42.2 43.3 44.4 45.6 46.7 47.8 48.9 50.0 51.1 52.2 53.3


Gear Chart for 20" X 1 3/8" wheels
Chainwheel 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Rear 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 70.5 72.0
Rear 15 47.6 49.0 50.0 51.8 53.2 54.6 56.0 57.4 58.8 60.2 61.6 63.0 64.4 65.8 67.2
Rear 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 61.7 63.0
Rear 17 42.0 43.2 44.5 45.7 47.0 48.2 49.4 50.7 51.9 53.2 54.4 55.6 56.9 58.1 59.3
Rear 18 39.7 40.7 42.0 43.2 44.4 45.5 46.7 47.9 49.0 50.2 51.4 52.5 53.7 54.9 56.0


Gear Chart for 24" X 1.50" wheels
Chainwheel 34   35  36 37 38 39 40 41 42 43 44 45 46 47 48
Rear 14 55.9 57.5 59.1 60.7 62.3 64.2 65.8 67.4 69.0 70.6 72.2 73.8 75.7 77.3 78.9
Rear 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 72.0 73.6
Rear 16 48.8 50.3 51.8 53.2 54.6 56.0 57.5 58.9 60.3 61.8 63.2 64.6 66.2 67.6 69.0
Rear 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 63.5 64.8
Rear 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 60.0 61.4


Gear Chart for 24" X 1.75" wheels
Chainwheel 34 35 36  37 38 39  40 41 42  43 44  45 46 47  48
Rear 14  58.3 60.0 61.7 63.3 65.0 66.9 68.6 70.3 72.0 73.7 75.3 77.0 78.9 80.6 82.3
Rear 15 54.4 56.0 57.6 59.3 60.7 62.4 64.1 65.5 67.2 68.9 70.3 72.0 73.7 75.1 76.8
Rear 16 51.0 52.5 54.0 55.5 57.0 58.5 60.0 61.4 63.1 64.5 66.0 67.4 69.1 70.5 72.0
Rear 17 48.0 49.4 50.8 52.2 53.6 55.1 56.5 57.9 59.3 60.7 62.1 63.6 65.0 66.2 67.7
Rear 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 62.6 64.1


Gear Chart for 24" X 1.1/8" wheels
Chainwheel 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Rear 14 54.9 56.5 58.1 59.7 61.3 63.1 64.7 66.3 67.9 69.4 71.0 72.6 74.4 76.0 77.5
Rear 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 70.8 72.4 
Rear 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 66.5 67.9
Rear 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 62.4 63.8
Rear 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 59.0 60.4


Gear Chart for 24" X 1.3/8" wheels
Chainwheel 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Rear 14 58.3 60.0 61.7 63.3 65.0 66.9 68.6 70.3 72.0 73.7 75.3 77.0 78.9 80.6 82.3
Rear 15 54.4 56.0 57.6 59.3 60.7 62.4 64.1 65.5 67.2 68.9 70.3 72.0 73.7 75.1 76.8
Rear 16 51.1 52.5 54.0 55.5 57.0 58.5 60.0 61.4 63.1 64.5 66.6 67.4 69.1 70.5 72.0
Rear 17 48.0 49.4 50.8 52.2 53.6 55.1 56.5 57.9 59.3 60.7 62.1 63.6 65.0 66.2 67.7
Rear 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 62.6 64.1

Is your bike set up properly?
Just like people are built different, bikes are built different too. Use the sizing charts on this page to help you make sure your bike is set up properly.

How do I know what size frame I should ride?
Use the chart below to help you decide what size frame you should be riding.

Frame Sizing Chart
Frame Size Micro - Mini Mini Junior Expert Expert XL Pro Pro XL Pro XXL
Top Tube Lenght 15"-16" 16"-17.5" 17.5"-18.5" 18.5"-20" 19"-20" 20"-20.5" 20.5"-21" 21"-22"
Riders Height 4'0" & under 4'0"-4'6" 4'4"-4'10" 4'8"-5'4" 5'2"-5'8" 5'6" - 5'10" 5'10"-6' 6' & over
Riders Weight 40-65 lbs 50-85 lbs 60-100 lbs 70-110 lbs 75-125 lbs 100 lbs & over 140 lbs & over 160 lbs & over

How do I know what size wheels I should ride?
Use the chart below to help you decide what size wheels you should be riding.

Wheel Sizing Chart
Riders Age Under 5 5 to 10 9 to 12 12 to 14 14 to 19 19 & up
Riders Weight 55lbs & below 55-80lbs 80-115lbs 115-145lbs 145-190lbs 190lbs & up
Wheel Size 18 x 1" 20 x 1-1/8"
24 x 1-1/8"
20 x 1-3/8"
24 x 1-3/8"
20 x 1.50
24 x 1.50
20 x 1.75"
24 x 1.75"
20 x 2.00"
24 x 2.00"
It is recommended riders who weigh 145lbs or more should run atleast a 20 x 1.75 tire on the front wheel.

 

 

 

 

How do I know what size cranks I should ride?
Use the chart below to help you decide what size cranks you should be riding.

Crank Sizing Chart
Inseam up to 15" 15" to 16" 16" to 17" 17" to 18" 18"- 20" 20" - 24" 24" - 28" 28" - 30" 30" - 32" 32" - 34" 34" +
Crank Length 135 mm 140 mm 145 mm 150 mm 155 mm 160 mm 165 mm 170 mm 175 mm 180 mm 185 mm

How do I know what size stem I should ride?
Use the chart below to help you decide what size stem you should be riding.

Stem Size Chart
Rider Height 4'0" & Under 4'0" - 4'6" 4'4" - 4'10" 4'8" - 5'4" 5'2" - 5'8" 5'6" - 5'10" 5'10" - 6'1" 6' & Over
Stem Size Mini Mini / Mini XL Mini/ Mini XL Pro Pro Pro / Pro XL Pro / Pro XL Pro XL / Pro XXL


 

General bike information if you plan on racing.

Any standard BMX bike will do. So before you go investing $100's of dollars in a race bike, start off on what you have or something low cost. If you decide you like it and want to stay racing, then start looking or building that perfect race bike.

Handlebars can not exceed 30" in width. Handlebar grips are required & must be sufficient to fully cover & enclose all  metal & openings on the handlebar ends.

You can not have the following items on your bike.

Reflectors -Freestyle Pegs - Kickstands - Chain Guards - Front Brakes

Rider requirements.

All riders must wear the following:

Helmet (preferably full-faced) with a working strap, no snaps.
Pants.
Long sleeve shirt.
Enclosed shoes.

 

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