BMX Frame Geometry information

What size BMX frame should I ride?

We recommend that riders from 160 - 180cm tall should choose a top tube length between 20.25 and 21 inch.

Riders 180cm and taller should choose 21 inch top tube frames and up. A shorter size frame could be chosen for street riding or competition park style riding, while a longer frame could be chosen for bowl riding or trail riding.

What is a '21"tt'?

BMX frames are typically sized in inches, with the top tube, or 'tt', being the determining factor for suiting riders of different heights.

So in this example, a '21"tt" refers to a 21 inch top tube length frame.

What type of BMX frame geometry is best?

The short answer is, there's no 'best frame geometry'. Frame geometry differs to suit different styles of riding.

Generally the shorter the chainstay and top tube, the more suited to quicker spins and movements, while a longer chainstay and top tube provides a more stable ride.

BMX frame geometry terms

Top tube length: The distance measured from
the center of the head tube, to the center of the seat tube.

The top tube length is the only factor that comes into play when looking for
a BMX frame size that suits your height, as it provides more room
between your seat and handlebars.

Head tube angle: The angle of the head tube from the ground.

Generally anywhere from 74° to 76°. The bigger the
number, the steeper the head tube angle, which translates to faster

You will find steeper head tube angles on BMX frames that are
catering towards street riding and quick movements, while mellower head tube angles allow for a more stable bike at higher speeds. 

Stand over height: The length of the seat tube, measured from the center of the bottom bracket, to the center of
the top tube.

The stand over height gives a BMX frame more stability by
having more frame under your legs! A taller stand over can also help
with tricks like barspins, as your seat is higher. On the contrary, a
low standover will help move your legs over the frame for tricks like

Chainstay length: The length of the
chainstay (bottom rear triangle tube), measured from the center of the
bottom bracket to the dropout. Generally distances between 12.5 to 14.8
inches. This measurement affects being able to lift the front wheel off
the ground, as well as ability to spin a BMX bike quickly, due to change
of distance between the wheels. A shorter chainstay length comes at a
cost of stability at faster speeds.

Bottom bracket height: The height of the
center of the bottom bracket shell from the floor, measured based off a
20 inch wheel in the dropouts. Generally ranging from 11.3 - 11.8
inches. The bottom bracket height determines your center of gravity on
the bike. A higher bottom bracket creates a lively feel BMX frame, while
a lower bottom bracket makes it more stable.

Seat tube angle: The angle of the seat tube
from the ground. Generally anywhere from 69°to 72°. The smaller the
number, the further back the seat would be, giving you the feel of
a larger BMX frame without having to make any other measurement larger. 

Looking for a BMX frame?

Whether it's swapping out your tired current frame, or upgrading your complete bike frame to an aftermarket BMX frame, there's no better feeling than bolting on a new BMX frame.

Riding a new BMX frame can be the best investment you've ever made in your riding lifetime. The sturdiness and 'pop' you feel is unlike anything else.


There's a lot of options, a lot of features, a lot of geometry.. a lot of things to get confused by.

Take yourself from unsure, to confident that you'll be choosing the absolute best BMX frame for your needs.

3 easy ways to find the best BMX frame for you:
  1. Find the right top tube length:
    Does the frame you're about to buy have the top tube that suits your height style of riding?

    You don't want to feel cramped and you don't want to feel like you're riding a cruise liner, either.

    Let's start by saying this is a guide only, it's going to be up to the individual at the end of the day!

    But here's how we work it out.

    As a standard, a general rider 180cm (5ft 10inch) should ride a 21" top tube frame with a 0.1" deviation +/- (20.9" - 21.1")

    For every 5cm (2 inches) taller, you should move up 0.25" in top tube (tt) length.

    Similarly, for every 5cm shorter, you should move down 0.25" in tt length.

    Example: General Rider 170cm tall = 20.5" tt (20.4" - 20.6" tt)

    Variants: If you are a BMX rider who rides trails or prefers to jump stuff, you would add 0.25 inches to the top tube length.

    Example: Rider 185cm tall has a standard 21.25" tt (21.15" - 21.35" tt) + top tube increase for jumping of 0.25 inches =
    New recommended size 21.4" - 21.6" tt

    There will always be individual preference, but if this is your first BMX frame buying experience, we'd suggest breaking out the calculator so you can make sure you're looking at the best size BMX frame for your needs.

  2. Choose the right features:

    If you do a lot of grinding and street riding, make sure the frame you're drooling over has things like:

    - Ovalized or dent resistant down tubes. Some frames even offer ovalized chainstay tubing for extra toughness
    - Chain tensioners to keep your wheel in place while grinding (because that peg wants to spin loose while you're grinding)
    - A higher bottom bracket can be beneficial for certain grinds
    - A shorter chainstay length can help for spins in and out of grinds.
    - Some frames are fully brakeless (no removable brake tabs) for an even cleaner look.

    If you're a park rider, features you may want to look out for:

    - Frames that offer removable or welded (very rare) gyro tabs
    - A lower standover (8 inches or less) can help with getting your legs over while tailwhipping
    - Steeper head angles (75°+) can help with rotational tricks

    If you're the type of rider to be tearing through the deep end of a concrete bowl, or sweating it out riding trails, then no doubt you'll want:

    - A mellower head tube angle (74.75° or less) to keep your bike feeling stable while going fast
    - Chainstay brake mounts for the classic trails look
    - Disc brake mounted trail frames are now appearing for an easier way to stop if things go wrong
    - Taller stand over height can give your bike a more stable feel
    - Lower BB heights (11.625" or less) will give you a lower center of gravity and more stability at higher speeds
    - Gussets play a crucial role in trusting your frame while riding big sets.

  3. Are you choosing a new BMX racing frame?

    You can race just about any frame (as long as the abillity to run brakes), but if you're in the market for a specific BMX race frame, then a bunch more factors come into play.

    While the features and geometry plays just as much of a factor for your new racing frame, it is important to make sure that your frame will build up to your existing parts.

    Pay special attention to:
    - Head tube size (1 inch, 1-1/8" or tapered 1-1/8" - 1.5") as this will determine how easy your current forks and headset will fit.
    - Seat tube diameter can vary between brands and sizes, so double check the size will meet your needs, or buy a suitable seat and post as well as the correct seat post clamp.
    - Bottom brackets can vary between sizes and brands, so make sure you can get a BB to suit your cranks.
    - Does your new BMX race frame use disc brakes or V-Brakes? Make sure you can use the brakes you intend to, including any adapters in your cart.

Now you are ready to get a new BMX frame.

If you have any questions or are trying to find a product that isn't showing up on the website, 99.9% of the time we can get it (or we have it and it's not showing), contact us with anything BMX frame related and we'll sort you out.