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BMX Bike Sizing

Choosing the right size BMX Bike!

Subrosa Tiro

A lot of people look at BMX as being a simplistic bike; just a BMX. Most of the people couldn’t tell you the difference between department store disaster and a purpose-built machine, but we know better! We know the kind of engineering and design that goes into making a BMX capable of the handling punishment we dish out. Basically, we know not all BMXs are created equal.

First things first, size does matter! However, it’s not a matter of bigger is better so let us explain:


The Top Tube (TT) is the top tube on a BMX bike frame that connects the front of the bike (HT) and the seat post tube (ST). Like any bike, there are different sizes to suit different size riders. Here is an approximate guide to BMX Bike Sizing:

Height / Discipline



Under 100cm

(Under 3’3”)

12” Wheel Size Balance or Pedal

(Based on confidence)

12” Balance*

Class Size

99cm – 122cm

(3’3” to 4’)


Wheel Size

Micro Mini*

Class Size

122cm - 137cm

(4’ to 4’6”)

16” – 18”

Wheel Size


Class Size

137cm – 147cm


18” – 20”

Wheel Size (Small TT size)


Class Size

142cm – 177cm


19.5” – 20.4”

Top Tube Length


Class Size

162cm – 178cm


20.25” - 21”

Top Tube Length


Class Size

172cm – 180cm



Top Tube Length

Pro XL

Class Size

180cm +

6ft +

21” - 22”

Top Tube Length


Class Size


Next to consider is what kind of riding will you be doing:

Most complete bikes will sit somewhere in the middle, and will be fairly well setup to take on most things, with the exception of some higher end bikes which are clearly orientated towards a more specific discipline.

  BMX Bike Wheel Sizes

Next up, lets talk price points - Key things to look for are:

Now that we have touched on sizing, let’s get a little more involved. When looking at bikes, what is the first thing you notice? Most of the time, it will be the price.  But, what do you get for your money?

Up to $550:

Bike will feature economical parts, Hi-Ten Steel, single-wall rims and mostly unsealed bearings. These bikes are for entry level guys that aren’t as likely to take BMX too far. Most sizes will be under 20.5”.

$550 - $800:

Now you’re starting to get Cro-Mo Main tubes and mostly sealed bearings. You will start seeing double wall rims, parts based on pro models and sizes will typically run between 20.4”-20.8” top tubes.

$800 - $1000:

Full Cro-Mo frame, fork and bar, some after-market parts and premium quality components. These bikes will normally size from 20.5”-21” top tubes.

$1000 and up:

Now you’re playing the real game. Full Cro-Mo parts and littered with pro model parts and accessories. Most of these bikes (if not all of it), you could pick off a shelf part for part. This is the big leagues and will be sized to suit.


-Hi-Ten: Hi-Ten or High Tensile Steel. Cost effective to manufacture, easy to work with and stronger than your average mild steel.

-Cro-Mo: Chromoly Steel is a mixture of Chromium and Molybendium to form the most popular steel available in BMX. This is lighter and stronger than Hi-Ten Steel.

-Heat Treating: On high-end bikes, you may come across “heat treated” steel. What this is, is a special process of heating and cooling the steel, after welding to increase the strength of the Cro-Mo steel tubing.

Typically, you can make a fair judgement on what the quality material is being used, based on price range.

Other key things to take into account:


-Unsealed Bearings: These are loose bearings or bearings in a cage that sit in a purpose-made race. Under abuse, these may need to be tensioned and maintained. For a basic bike, these are fine, however, they will not be as good as sealed bearings.

-Sealed Bearings: Sealed bearings means that a sealed cartridge bearing is being used. In BMX these typically mean they are higher quality, will take more abuse, have less maintenance, and generally last a lot longer than Unsealed bearings. This is something you should look for in any high-quality complete.

Semi-Sealed: A mixture of sealed and unsealed bearings. Normally this will relate to the rear wheel.


-Single Wall Rims: Refers to the inner wall of the rim itself. Single wall rims are your standard rim, with only one horizontal wall. If it doesn’t say double wall, you can be safe to assume it is a single wall.

-Double Wall Rims:This means you have two horizontal walls in your rim, which, means more strength. The shapes in which these walls and ribs run can vary, but if it says double wall, you can expect it to be much higher quality than a single wall rim.

Now you should have everything you need to get the right bike, right size and right price!

You can always give us a call or drop into the store and check out the range of bikes we have available.

The most important thing to consider when buying your new bike is: The one you like most, is the one you will ride most!

BMX Bike Range

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