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South Park BMX Map

800 East Park Drive
Bethel Park PA 15102
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Jonathon Spynda

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BMX Race - Size Charts

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


BMX Race - Size Charts

The charts below are provided to help “guide” you to the right size equipment. Please keep in mind they are guidelines. Ideally, the best way is to try a loaner bike or borrow a bike and gear to see you how feel.


FRAME size

BMX 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 center of the seat tube to the center of the head tube. 

To determine your frame size, you must measure you height. Take off your shoes and remove anything from your head. Put a book on top of your head and mark the place on the wall where the bottom of the book is resting. Then measure from the floor to the pencil mark with a measuring tape. 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.

We get a lot of new parents and riders 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 we 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 staff to try our 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. We 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 West Newton Bike Shop and ask for Floyd, a/k/a The Bike Doctor. He has a wealth of knowledge and will be glad to size you up.






15.25" to 16.50"

UP TO 4'


16.75" to 17.50"

4' to 4' 4"


17.75" to 18.50"

4' 3" to 4' 7"


18.75" to 19.50"

4' 6" to 5' 5"


19.75" to 20.50"

5' 4" to 5' 8"


20.75" to 21.50"

5' 8" & UP





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 145 lbs 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

55lbs & below

Under 5

18 x 1'

55 -80 lbs

5 to 10

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

80 - 115 lbs

9 to 12

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

115 - 145 lbs

12 to 14

20 x 1.5
24 x 1.5

145 lbs +

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.


Where can I purchase BMX Race parts?

Local Bike Shops:

  • West Newton Bike Shop
  • Pro Bikes
  • Performance Bikes
  • Iron City Bikes


On-Line Bike Shops:

  • J&R Bicycles –
  • Powers Bike Shop –
  • Fly Racing –
  • Faith Race Apparel –
  • G-Form Protective Gear –