Sizing For BMX Bikes – Bicycles In Motion

Sizing For BMX Bikes

Sizing For BMX Bikes

Micro BMX isn’t the smallest size, and Pro XXL isn’t the largest, but frames that fall outside the norm don’t have names and are typically custom.

However, there is a ton of variation within the named frame sizes and plenty of overlap, so everyone can ride the way they’re most comfortable. How do you choose a BMX size?

Choosing the correct sizing for BMX bikes is relatively simple because all you need to know is the rider’s height, but you can also make an educated guess based on their age. BMX bikes are versatile enough that the size is mostly about comfort and riding style. A racing BMX is a little different from a freestyle bike.

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How To Choose A BMX Bike Size

Choosing a BMX size is not a complex process. The size you need is based on frame size, and the frame size is measured by top tube length.

The tire sizes don’t change much, so both a small child and a tall adult can (and do) ride 20-inch tires.

You need to measure the metal bar at the top of the bike’s frame. This will be just below the saddle (seat) and handlebars.

The length of this piece will tell you what the frame size is called, and it directly correlates to how tall you are. The taller the rider, the longer the top tube should be.

Riding an oversize BMX can be harder to control. Similarly, if your bar rise is higher, it is harder to control but easier to pull up when doing tricks. Finding a balance between comfort and function is essential.

It would help if you decided whether your BMX will be for racing or freestyle before starting your search. The difference is not size but rather in the frame material.

Many new riders make a critical mistake in thinking that the frames will somehow look significantly different.

Most BMX bikes are either Chromoly or aluminum. Racing frames are built lighter so you can move fast, but freestyle frames are made tough, so they can handle stunts and landing tricks hundreds or thousands of times.

Sizing Chart For BMX Bikes

Selecting the best BMX bike starts with finding the right size. Below I’ve created a simple chart to help you figure out where to start.

It’s vital to understand that BMX bikes are rugged and built to withstand impacts for jumping and the pressures of racing, so weight is rarely a factor.

If the manufacturer lists a weight limit, please abide by it to prevent injuries, but otherwise, you should be able to ride any of these styles.

BMX Bike Size Chart By Frame Size & Rider Height

Frame SizeRider HeightRider Age (general)Bar RiseBar WidthStem LengthToptube Length
Micro4’4″ & under2 – 10 years2″ – 2.5″20″ – 22.5″25mm – 35mm15″ – 16.5″
Mini4’2″ – 4’10”8 – 11 years2″ – 3.5″21″ – 23.5″30mm – 40mm16″ – 17.5″
Junior4’6″ – 5’1″10 & up3″ – 5″22″ – 25″40mm – 45mm17″ – 18.5″
Expert5’0″ – 5’4″13 & up5″ – 7″25.5″ – 27″43mm – 48mm18.5″ – 19.5″
Expert XL5’2″ – 5’6″13 & up6″ – 7″25.5″ – 27″43mm – 48mm19.5″ – 20″
Pro5’3″ – 5’8″13 & up7″ – 8″27″ – 28″50mm – 55mm20″ – 20.5″
Pro XL5’7″ – 6″13 & up8″ +28″50mm – 55mm20.5″ – 21.25″
Pro XXL6″ +13 & up8″ +28″52mm – 60mm21.25″ – 22″

You may have noticed the overlap in sizes. This is due to rider comfort. Humans of the same height are not necessarily built the same, and the way they ride changes as a result.

For example, two people who are 5’6″ can have different inseams with longer or shorter legs and different arm lengths.

Most people follow a general pattern, but it’s not immutable. Moreover, the way you carry your weight changes your center of gravity by up to several inches, changing your posture and how you sit on or stand over your BMX.

Try a different toptube length or longer stem if your frame isn’t comfortable. Adjust your bar rise up or down when your arms are sore from overextension or wrong positioning.

BMX bikes are easy to customize.

BMX Wheel Size Chart

Wheels are just as crucial as the toptube size, but there’s not much variation within the BMX bike style.

I put together a basic chart showing frame size, rider height, and the wheel size you need.

As always, these are guidelines, and you can adjust up and down for comfort as long as the wheels fit your frame.

Frame SizeRider HeightWheel Size
Micro4’4″ & under12″ 14″ or 16″
Mini4’2″ – 4’10”14″ or 16″
Junior4’6″ – 5’1″16″ 18″ or 20″
Expert5’0″ – 5’4″20″ 22″ 24″ or 26″
Expert XL5’2″ – 5’6″20″ 22″ 24″ or 26″
Pro5’3″ – 5’8″20″ 22″ 24″ or 26″
Pro XL5’7″ – 6″20″ 22″ 24″ or 26″
Pro XXL6″ +20″ 22″ 24″ or 26″

What Size BMX Stem Do I Need

BMX stems hold the handlebars. The rise of your stem makes the overall height of your handlebars taller, and it can make it more comfortable to ride or easier to control.

A front-load stem won’t add much height, but a top-load stem raises the handlebars slightly.

As Dougsterbob points out, “Top load stems are a little stronger because of the block of metal supporting the bars. Upon impact or cases, the weight and pressure are absorbed by the core of the stem instead of the bolts.”

BMX Stem Size Based On Your Frame

Choosing the right stem will make your frame feel longer because it extends the handlebars out in front of you further.

Additionally, the slight height boost can help keep your shoulders comfortable as you ride and make it a little easier to lift the front end as you jump.

Here’s a list to help you get the correct stem size:

  • Micro: 25mm – 35mm
  • Mini: 30mm – 40mm
  • Junior – Expert: 40mm – 45mm
  • Expert – Pro: 43mm – 48mm
  • Pro – Pro XL: 50mm – 55mm
  • Pro XXL: 52mm – 60mm

Are BMX Bikes Supposed To Be Small

BMX bikes are smaller than cruisers and mountain bikes. However, they aren’t the only small-sized bike.

For example, road bikes are about the same size as a BMX, and both are more diminutive than their big cousins.

Yet calling them ‘small’ isn’t quite right since BMX’s are the size they’re meant to be, and ‘small’ often implies undersized.

Can Tall Guys Ride BMX

Tall guys can ride BMX. These bikes are built tough and can handle the weight.

Moreover, height is not a limiting factor for bike riding, and there are even famous BMX riders like Van Homan, David Grant, and Big James who are known for their height as much as their incredible skills.

What Age Is A 20, 24 & 26 Inch BMX Bike For

BMX bikes are not sized by rider age but rather by their height. When you see the sizes listed as 20″, 24″, and 26″, this refers to the tire size, but those tires fit on many different frame sizes.

Typically, a 20-inch tire is for anyone from kids over 10 to adults.

Because BMX isn’t sized the same as other bikes, this can cause some confusion. Size 20″ wheels are standard for any frame from a Junior to a Pro XXL. This size is considered the ‘true’ BMX tire size.

A short, low-to-the-ground body and small twenty-inch wheels are iconic parts of this bike style.

Micro’s Mini’s and Juniors sometimes have smaller tires because smaller children and short adults ride them.

Likewise, any size from Expert to Pro XXL can have larger tires, but that is a variation outside the norm for a BMX.

For more information on what size BMX you need, I recommend checking out this excellent video by Brant Moore.

He explains how to tell what size frame you need and why it’s all about rider height. Plus, he also talks about mods and adjusting based on what feels comfortable for you.

Helpful Tips To Know About Sizing For BMX Bikes

Once you know the rider height and toptube length, you can find a basic BMX in the correct size.

However, sizing is always a matter of personal preference, especially in the world of BMX, where custom work is typical.

Here are more helpful tips to know about sizing for BMX bikes.

  • Your shoulders and arms should not hurt after riding a BMX. If you find they feel abnormally strained, consider swapping your handlebars out for a set with a higher or lower rise. Other than frame size, this is one of very few essential elements you can adjust easily for a more comfortable fit.
  • It’s completely okay to decide that you need a larger or smaller frame size than the one that is generally meant for your height. Riders may find a shorter frame gives them more control, or a longer frame feels better as they ride. The chart above is a general size guide only, and I recommend customizing your BMX to fit the way you enjoy riding.
  • BMX is an abbreviation of the words bicycle and motocross. These bikes were made to do the same racing and stunt tricks as motocross riders, but without the engine, so they are ideal for parks, dirt tracks, and road riding.

Final Thoughts

BMX bikes are a ton of fun to ride but getting into racing or freestyle can be confusing if you don’t know how to size your bike.

Choosing the right fit is based entirely on your height and the length of the toptube on the bike.

A shorter frame offers more control but can feel cramped, while too long can feel unstable or offer a more relaxed, stretched-out position.

The bar rise on your handlebars has a similar effect, with lower bars offering the best control.

However, the nicest thing about BMX is that the sizing is easy to customize, and you can easily swap out parts to get your ideal ride.

Brian Smith

Brian is the founder of Bicycles In Motion and an avid cyclist for 17 years. On the weekends, he enjoys exploring new bike trails and countryside roads to enjoy the outdoors.

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