Frame Size Chart
Wondering what size Frame is right for you? Check out the chart below and maybe it will help narrow down those decisions.
Rider Height Frame Size Top Tube Length
4'0" & under Micro-Mini 15"-15.5"
4'0"-4'6" Mini 15.5"-16.5"
4'4"-4'10" Junior 16"-17.5"
4'8"-5'4" Expert 17"-18.5"
5'2"-5'8" Expert XL 18"-19"
5'6" - 5'10" Pro 18.5"-19.5"
5'10"-6'1" Pro XL 19"-21"
6' & over 6' & over 20.5" & over
Crank Arm Length Chart
Wondering what size Crank Arm is right for you? Check out the chart below and maybe it will help narrow down those decisions.
Rider Inseam Crank Arm Length
20" 140 mm
21" 145 mm
22" 150 mm
23" 155 mm
24" 160 mm
25" 162 mm
26" 166 mm
27" 171 mm
28" 175 mm
29" 177 mm
30" 180 mm
31" 182 mm
32" 185 mm
33" 185 mm
34" + 190 mm
Stem Size Chart
Wondering what size of Stem is right for you? Check out the chart below and maybe it will help narrow down those decisions.
Rider Height Stem Size
4'0" & Under Mini
4'0" - 4'6" Mini / Mini XL
4'4" - 4'10" Mini/ Mini XL
4'8" - 5'4" Pro
5'2" - 5'8" Pro
5'6" - 5'10" Pro / Pro XL
5'10" - 6'1" Pro / Pro XL
6' & Over Pro XL / Pro XXL
In BMX racing, the gears you run can make or break you. It's important that you know how to change gears and when. Track conditions and other factors may warrant a gear change. 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 (or freewheel) turns for every full 360 rotation of your front sprocket (or chainring).
It's really simple; you 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. Easy enough? You can use this formula to help solve common problems. For example, which gear size is bigger - a 42/15 or a 45/16? Unless you have a gear chart handy, this formula is the only sure way to answer that question. In doing the math, you'll find that a 45/16 gear ratio is just slightly bigger than the 42/15.
If your gear size is large (about 58 or greater), you will go faster, but you will accelerate slower; it will take longer to get going and 'wind out'. 'Winding out' or 'topping out' refers to when you are at top speed; pedaling the bike does not make it go any faster. Snapping out of the gate, going uphill, powering out of turns, etc. will be harder with a high gear. Conversely, a low gear size (about 52 or less) will result in faster acceleration, but lower overall speed. For most racing situations, a 55 gear size is almost perfect; not too high, and not too low. However, a different gear may be more appropriate, depending on track conditions. The overall slope of the track (uphill, downhill, etc.), length of the track, angle/slope of starting gate/hill, overall track layout, and the track surface are just some of the conditions that might warrant a gear change.
Experiment with different gears and see what works best. You'll be glad you did.
Gear Size Chart
Wondering which gears you should be running? Check out the chart below and maybe it will help narrow down those decisions. 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 1.75" 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 61.9 62.7 64.1 65.5 66.9
Rear 15 44.3 45.4 46 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 52.7 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 1.50" 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 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 52.8 53.9 55.5 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 1.3/8" 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 50.4 51.6 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 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 57.1 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 45.0 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 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 50.0 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 1.50" 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 48.4 50.3 51.8 53.2 54.6 56.0 57.5 58.9 60.3 61.8 63.2 64.6 66.2 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 1.3/8" 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 71.3 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 66.0 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 63.3 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 77.6
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
