How do I know what size bike and parts I should ride?

How do I know what size bike and parts I should ride?

BMX Race - Size Charts

It is strongly recommended to try a loaner bmx race bike or borrow a bike and gear to see your child feels. the charts below are provided to help “guide” you to the right size equipment. be sure to keep in mind these are only guidelines and one size doesn't fit all in BMX racing. 


FRAME size

BMX racing bikes come in many different sizes--from micro, mini, junior, expert, expert XL, PRO, PRO XL, etc.  A frame’s size is determined by measuring the top tube length of the frame. The top tube (tt) measurement is taken from the centre of the seat tube to the centre of the head tube. 

To determine your frame size, you must measure your little BMX racers height. Take off their shoes and measure to top of head. Find your size on the chart below. This should get you into a good ballpark for size by using the chart below. Though these charts provide a good model, it is not a science. Frame size will always vary slightly with a rider’s overall body size and build.

A lot of new parents and riders are asking what size BMX frame they or their child should ride. There are a ton of frame size charts out there an almost every bike shop and manufacturer has one. The rule of thumb to go by is to try a couple loaner bikes from the track in different sizes and see which one fits best.

Ideally, the best way to size a bike to a rider is to ride them. Ask any of the track officials at your local BMX race track to try a loaner bikes. Take it for a spin and see how you or your rider feels on the bike. Some like to be stretched out and others ride more upright. you see this all the time. Though you would expect every rider to ride a certain frame or bar and then they want something different based on your particular build and riding style. It may take some trial and error, but this is the most accurate way.  

If you’re unable to stop by the track to try a loaner bike, we recommend you stop by your local BMX track or bike store.






15.25" to 16.50"

UP TO 120cm


16.75" to 17.50"

120cm to 140cm


17.75" to 18.50"

130cm to 150cm


18.75" to 19.50"

145cm to 160cm


19.75" to 20.50"

165cm to 175cm


20.75" to 21.50"

170cm to 180cm

 there is multiple other sizes available but these are the most popular.




A common mistake is to buy crank arms that are too long. Arms that are too long make the rider swing their bike side-to-side., “wag your tail’ and ride in a zig-zag line instead of a straight line. If the arms are too short, they will not give enough leg extension or enough power. The key is to buy the right size for your legs. You can do that by measuring the inseam of your rider’s leg.

If you purchase a complete bike, you will want to make sure the crank arms are the right size for your rider. To determine the crank size, you measure the rider’s inseam.



Tire size corresponds with the rim size shown on the chart below and primarily based on the Rider’s weight. Riders who weigh 65 kgs or more should run at least a 20 x 1.75 tire on the front wheel. Skinnier tires lighten up a bike but wider tires will give more traction in the turns.

Wheel/Tire Sizing Chart



Wheel/Rim Size

25kgs & below

Under 5

18 x 1'

25 -36 kgs

5 to 10

20 x 1-1/8
24 x 1-1/8

36 - 50 kgs

9 to 12

20 x 1-3/8
24 x 1-3/8

50 - 65 kgs

12 to 14

20 x 1.5
24 x 1.5

65 kgs +

14 +

20 x 1.75
24 x 1.75



What other BMX bike parts should I check over?



Every 6mm of stem length is equal to a 1/4". You will always want to try to run the shortest stem possible for the frame to make sure the steering is proper. The longer the stem, the more "Oversteer" you will feel.



Typically, you want your bars in line with your head tube angle for proper handling. You can pull them back slightly to bring your bars back for a shorter rider area, but do not go back to far. In addition, the same going forward, you can push them forward slightly, but do not "Chicago" your bars. Never go past Vertical on your bar set up.

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