So you want to get your child a good BMX race bike. But what size do they need? What brands are good? What else do you need to consider?
This guide is here to help you figure all of that out. We’ll go over the sizes of BMX race bikes, which size your child needs, the best brands and their offerings, and other things you should think about when buying your child a new bike.
Kids BMX Bike Sizes Explained
If you’re new to BMX racing, the bike sizing can be very confusing at first. The naming convention is very different than most kids bikes which are sized by their wheels–i.e. 12 inch bike, 14 inch bike, etc.
There are four sizes of kids BMX racing bikes:
- Micro Mini (under 5)
- Mini (5-7)
- Junior (7-9)
- Expert (9-11)
- Expert XL (10-13)
Teens can fit on a regular adult (Pro) BMX bike, so we won’t focus on those in this article. That said, if you’re looking for a BMX racing bike for your teen, you can still choose a bike from one of the brands we list below.
BMX Bike Size Chart
If you’re not sure which size BMX bike your child needs, this chart should help as a good starting point. Keep in mind that height is a better indicator than age. As we all know, kids grow at different times.
It’s also helpful if your child can try some of these sizes before buying, especially if they are right in between sizes. Many local tracks offer a rental or loaner program.
| Size | Age | Height |
| Micro Mini | <5 | 3’6″-4’0″ |
| Mini | 5-7 | 4′-4’4″ |
| Junior | 7-9 | 4’3-4’7″ |
| Expert | 9-11 | 4’6″-5’5″ |
| Expert XL | 10-13 | 5’3-5’7″ |
Kids BMX Race Bike Brands
Listed below are our favorite brands for kids BMX race bikes and their line-ups. Whatever age or size of your child, you’ll find a bike for them.
DK
DK makes great BMX race bikes and they are (relatively) affordable which makes them attractive for families just looking to try out the sport. In fact, this is the brand we got for my son’s first BMX bike..
They have two different models across sizes–the Swift and the Sprinter. The latter is $150 more but has upgraded components and comes in a little lighter.
Where To Buy:
DK Lineup
| Bike | Size | Price | Weight | Top Tube | Wheels/Tire | Crank |
| Swift Micro | Micro Mini | $499 | 16.3 lbs | 16.25″ | 18 x 1” | 120mm |
| Swift Mini | Mini | $499 | 16.3 lbs | 17.25″ | 20 x 1-1/8” | 140mm |
| Swift Junior | Junior | $499 | 17.3 lbs | 18.25″ | 20 x 1-3/8” | 155mm |
| Swift Expert | Expert | $499 | 20 lbs | 19.5” | 20 x 1-3/8” | 165mm |
| Sprinter Micro | Micro Mini | $649 | 15.9 lbs | 16.25″ | 18 x 1” | 120mm |
| Sprinter Mini | Mini | $649 | 16.1 lbs | 17.25″ | 20 x 1-1/8” | 140mm |
| Sprinter Junior | Junior | $649 | 17.1 lbs | 18.25″ | 20 x 1-3/8” | 155mm |
| Sprinter Expert | Expert | $649 | 18.5 lbs | 19.5” | 20 x 1-3/8” | 165mm |
GT
GT offers two series of kids BMX bikes: the Mach One and the Speed Series. The Mach One is intended as an affordable, entry-level race bike, while the Speed Series is meant for some serious racing. We appreciate that while the cost of nearly everything has gone up in the last year, the GT BMX prices have remained pretty steady.
Where To Buy:
GT Lineup
| Bike | Size | Price | Top Tube | Wheels/Tire | Crank |
| Mach One Mini | Mini | $450 | 17″ | 20 x 1-1/8″ | 140mm |
| Mach One Junior | Junior | $450 | 18.5″ | 20 x 1-3/8″ | 152mm |
| Mach One Expert | Expert | $450 | 20.75″ | 20 x 1-3/8″ | 140mm |
| Speed Series Micro | Micro Mini | $795 | 16″ | 20 x 1-1/8″ | 127mm |
| Speed Series Mini | Mini | $795 | 17.5″ | 20 x 1-1/8″ | 135mm |
| Speed Series Junior | Junior | $795 | 18.5″ | 20 x 1-3/8″ | 135mm |
| Speed Series Expert | Expert | $795 | 19.5″ | 20 x 1-3/8″ | 165mm |
| Speed Series Expert XL | Expert XL | $795 | 20″ | 20 x 1.5″ | 165mm |
Haro
Haro is well known for their freestyle and street BMX bikes, but they make great race bikes as well. New for this year, they only have one model of bike but that helps keep things simple. Most of the sizes have a v-brake, but the Expert XL offers a rear mechanical disc brake.
Where To Buy:
| Bike | Size | Price | Weight | Top Tube | Wheels/Tire | Crank |
| Micro Mini | Micro Mini | $639 | 15.5 lbs | 16.75″ | 18 x 1″ | 130mm |
| Mini | Mini | $639 | 15.7 lbs | 17.6″ | 20×1 1/8″ | 130mm |
| Junior | Junior | $639 | 16.3 lbs | 18.3″ | 20×1 1/8″ | 145mm |
| Expert | Expert | $639 | 16.8 lbs | 18.87″ | 20×1 3/8″ | 155mm |
| Expert XL | Expert XL | $689 | 19.4 lbs | 20″ | 20×1.65 F/ 20×1.50 R | 170mm |
Redline
Redline is one of THE original names in BMX. Like most of the other brands listed here, Redline offers two product lines: the entry-level MX and the higher-end Proline.
Where To Buy:
| Bike | Size | Price | Top Tube | Wheels/Tire | Crank |
| MX Mini | Mini | $465 | 18″ | 20 x 1-1/8″ | 140mm |
| MX Junior | Junior | $465 | 18.5″ | 20 x 1-1/8″ | 155mm |
| MX Expert | Expert | $465 | 19.5″ | 20 x 1 3/8″ | 165mm |
| MX Expert XL | Expert XL | $480 | 20″ | (F) 20 x 1.6″ / (R) 20 x 1.4″ | 170mm |
| Proline Expert | Expert | $650 | 19.5″ | 20 x 1-3/8″ | 165mm |
| Proline Expert XL | Expert XL | $650 | 20″ | 20 x 1.60″ | 170mm |
Jet
Jet offers simple, entry-level race bikes. This is a UK company, but you can get their bikes in the US via SourceBMX or Amazon.
Where To Buy:
| Bike | Size | Price | Top Tube | Wheels/Tire | Crank |
| Accelerator Mini | Mini | $339 | 17.5″ | 1-1/8” | 140mm |
| Accelerator Junior | Junior | $359 | 18.5″ | 1-1/8” | 150mm |
| Accelerator Expert | Expert | $369 | 19.75″ | 1-3/8” | 160mm |
Chase
Serious racers (and those with no budget), take note. Chase makes some of the nicest BMX race bikes around. This is the brand our son is currently riding on.
In addition to the complete bikes listed below, Chase also sells individual frames.
Where To Buy:
| Bike | Size | Weight | Top Tube | Wheels/Tire | Crank |
| Edge Micro | Micro Mini | 15.4 lbs | 16.25″ | 18 x 1″ | 130mm |
| Edge Mini | Mini | 16.7 lbs | 17.25″ | 20 x 1-1/8″ | 140mm |
| Edge Junior | Junior | 17.5 lbs | 18.75″ | 20 x 1-1/8″ | 155mm |
| Edge Expert | Expert | 18.6 lbs | 19.75″ | 20 x 1-3/8″ | 165mm |
| Edge Expert XL | Expert XL | 19.5 lbs | 20″ | 20 x 1.60″ F / 20 x 1.40″ R | 170mm |
| Edge Element Expert | Expert | 18.4 lbs | 20″ | 20 × 1-3/8″ | 165mm |
Supercross
If you are interested in building up a bike from the frame, check out Supercross. These frames aren’t cheap, but they do give you the option to create an amazing custom build.
Where To Buy:
| Frame | Size | Price |
| Envy Micro | Micro Mini | $699+ |
| Envy Mini | Mini | $699+ |
| Envy Junior | Junior | $699+ |
| Envy Expert | Expert | $699+ |
| Envy Expert XL | Expert XL | $699+ |
Things To Know Before Buying
Wheel And Tire Size
Most kids BMX bikes have 20 inch wheels. The exception is the micro mini bikes which have 18 inch wheels. (And cruiser bikes which have 24 inch wheels).
Tire width is the other thing to consider. The skinnier the tires, the lighter they will be. Fatter tires, on the other hand, provide additional traction.
You want to consider the type of track your child will be racing on. Many tracks have concrete start hills and paved corners. In this case, you can get away with skinnier tires. If the track is entirely dirt, than you may want a little wider tire with more traction for the corners.
Top Tube Length
Not all bikes that are “Minis” will have the same top tube length. The longer the top tube length the further the reach and the bigger the bike will essentially feel.
This means that if your child is on the bottom end of a size range, look for a bike with a shorter top tube length. Or, if your kiddo is on the bigger end but not yet ready to size up, consider a bike with a longer top tube length.
It’s also worth mentioning that different riders may prefer different fits. Some kids will prefer to be more stretched out in a more aggressive position, while others may prefer to be more upright. Again, trying some loaner bikes before buying can be helpful for this.
Crank Length
We see way too many kids riding a bike with crank arms that are too long. This can rob your child of power as well as simply being unergenomic.
The best way to determine which size crank length your child needs is to measure their inseam. Even if the bike you are considering has the wrong size cranks, this is always something you can swap out on your own.
| Rider Inseam | Appropriate Crank Length |
| 16″ | 120mm |
| 18″ | 130mm |
| 20″ | 140mm |
| 21″ | 145mm |
| 22″ | 150mm |
| 23″ | 155mm |
| 24″ | 160mm |
| 25″ | 165mm |
| 26″ | 170mm |
Gearing
BMX race bikes only have a single gear. This means that it needs to be the “right” gear, or your child will be spun out or struggling to turn over the pedals.
The good news is that you don’t need to worry about this too much when buying a bike, because you can always swap out the front or rear sprocket later. Still, most kids will want to run one of the combos below. (The first number is the number of teeth on the front chainring and the second number is the number of teeth on the rear cog).
44/16
39/14
36/13
33/12
25/9
Note that these are for 20″ wheels.
Weight
Remember, the heavier a bike is the more challenging it is going to be for your child to race on. The lighter the bike, the faster they’ll be able to go.
Of course, the lighter a bike, generally the more expensive the bike will be. In fact, serious racers will spend a lot of time and money upgrading components to build a bike as light as it can be.
Choose the lightest bike that is realistically within your budget.
Building a BMX Bike
If you are new to the sport, on a budget, or have limited bike mechanic experience, the easiest thing to do is to buy a complete bike like those listed above. That said, as your child progresses in their BMX career, there is a good chance that you’ll decide to build up a bike at some point.
Fortunately, BMX bikes are fairly simple and far easier to build that a mountain bike, for instance. You will need to buy a frame, fork, and components (wheels, handlebar, stem, chain and sprockets, pedals, saddle, etc….), but this can be a fun project to work on with your child.
Similarly, you can buy a stock bike and upgrade components as you go.
Buying A Used BMX Bike
The bad news is that kids grow out of bikes quickly. The good news is that this means someone is always selling their child’s bike.
We have had great luck buying our son used bikes. You can also find parts and components used if you’re thinking of building or upgrading a bike.
The best place to buy a used bike is at your local BMX track. Many people will bring bikes they are looking to sale to race or practice, and just throw a for sale sign on it.
Similarly, many BMX tracks have their own swap and sale Facebook pages. This is a great way to get a good deal.
Any recommendations for a bmx race bike smaller than the micro mini… Or the smallest micro mini available? Thx
U can swap 18 inch wheels onto a gt Mach 1 16 inch by slightly grinding front fork for clearance and running a road bike brake caliper to make an 18 inch micro wit a 15is inch top tube @troygreenebmx on ig and look back to around 2018/early 2019 for pictures of one black red and green bike, hope this helps