From Size to Brakes to Gears, We Guide You Through the Features that Really Matter
What size bike does my child need? This is probably the most common question we get from parents. Bikes, like kids, come in all shapes and sizes. They are not one-size-fits all, and even a bike that “technically” fits your child won’t necessarily be best for them. Some bikes are better for petite or timid kids, while others are better for taller or more aggressive riders.
Over the years we’ve reviewed almost 100 different bikes and concluded that there is no such thing as “the best” kid’s bike, but there are bikes that are best for various types of kids or budgets. Here are 7 main criteria that will help you choose the perfect bike for your son or daughter of any ability or age: 1) Size 2) Weight 3) Geometry (frame shape) 4) Brakes 5) Gearing 6) Bike Width and 7) Price.
1. What Size Bike Does My Child Need?
Size is the most important feature to get right when buying your child a new bike. If a bike is too big or too small, it’s going to be difficult and potentially dangerous for your child to ride. Kids’ bikes are categorized by tire size (the diameter of the tire). Most brands make models in 12″, 16″, 20″ and 24″ tires, while smaller brands and some big-box companies sell a 14″ bike. Most balance bikes come with 12″ tires.
Unfortunately, it quickly gets confusing because the actual size of a bike can vary drastically within a tire size category. As a result, seat height (compared to inseam) is by far the most accurate measurement for buying a bike with a proper fit.
Kids' Bikes Sizing Guide
2 - 3
|15" - 18"||3T||36" - 39"|
2 - 4
|15" - 20"||WOOM2, ByK E-250, Pello Romper||3T - 4T||37" - 44"|
4 - 6
|16" - 22"||4T - 5||41" - 48"|
4 - 6
|16" - 22"||Priority Start 16, Pello Revo, Raleigh MXR 16||4T - 5||41" - 48"|
5 - 8
|19" - 25"||6 - 8||45" - 54"|
8 - 11
|23" - 28"||WOOM5, Guardian 24"||10 - 12||49" - 59"|
|25" +||WOOM 6||12+||56"+|
If you’re a visual learner, check out our infographic: The New and Better Kids Bike Sizing Guide.
Kids’ bikes are categorized by tire size, and as kids get older and bigger, they also need bigger tires. 12″ bikes are generally for kids 18 months old to 4 years and are usually best for balance bikes. By the time kids are ready to transition to a pedal bike, they are usually ready for a 14″ or a 16″ pedal bike, versus a 12″.
The overall size of the bike, however, is not solely determined by tire size, which is why a vast range of ages can ride the same size tire. The height of a child (and their inseam measurement) is also a major factor.
While tire size is the most common indicator of overall size for kids’ bikes, the seat height is the most accurate indicator of how a bike will fit your child. Due to differences in frame design, bikes with the same size tire can fit a child very differently. The WOOM3 and Next Rocket are both 16″ bikes, yet there is a 4″ difference in their minimum seat heights. Most bike manufacturers do not state the minimum and maximum seat height of their bikes, so those measurements can be hard to come by. The seat heights of many bikes, however, can be found using our Kids’ Bikes: Product Filter Tool.
First Pedal Bike: A child’s first pedal bike needs to fit differently than his subsequent bikes. All kids just learning how to balance and/or pedal a bike need to be able to stop the bike with their feet. This applies to kids transitioning from a balance bike, a tricycle, or a bike with training wheels. As a result, a child’s inseam should match the minimum seat height on the bike so both of their feet can easily touch the ground (not just tippy toes). Even if a child can easily pedal and ride a bike with the training wheels on, the bike is still too big for him if he can’t touch the ground with both of his feet.
Here are a few additional seat height considerations based on your child’s ability:
a) Kids who are have mastered a hand brake on their balance bike may be able to ride a bike that has a minimum seat height of 1″ to 1.5″ taller than their inseam. If they can confidently brake with their hand, they only need to be able to touch the ground with their tippy toes.
b) Timid or less coordinated kids are always better off starting on a bike on which they can place their full foot on the ground.
c) More aggressive or eager balance bike graduates generally don’t have a problem riding a bike with a minimum seat height 1″ to 1.5″ taller than their inseam.
In all cases, never put a child on a bike that they cannot stop! Kids transitioning from balance bikes cannot rely on a coaster brake (back pedal brake) to stop until they have mastered pedaling, which can take time.
2nd Pedal Bike and Beyond: Having mastered the use of brakes, a child should no longer be depending on his feet to stop. A child should be standing on his tippy toes when seated on the seat in order to allow for proper leg extension when pedaling. If they can place their entire foot on the ground, they can’t get proper extension on the pedal, causing each pedal stroke to be much more inefficient.
When purchasing a bike, especially a 20″ or 24″ kids’ bike when the child’s inseam is always less than the minimum seat height, it is also important to take note of a bike’s standover height. The standover height is the height required to stand over the top tube of the bike (the top tube of the frame that connects the front of the frame to the back). When standing over the bike (not on the seat) there should be an inch or two of clearance. The gap helps prevent injury if the child slips forward off the seat during a fall. Most top tubes of kids’ bikes are slanted downwards for this reason. For really aggressive riders, it also allows for more clearance when leaning into a turn. The “standover” height is a common measurement provided by both big and small bike manufacturers.
Measuring Your Child: The easiest way to measure a child’s inseam is with a hardbound book. Without shoes on, have the child stand against a wall, squeeze the book between their legs, and then slowly raise the book up until it hits their crotch. Level the book with the floor, then measure the distance between the top of the book to the ground.
2. How much should my kids’ bike weight?
Most adults ride bikes that are about 20% of their total weight, while kids’ bikes are usually around 50% of their weight! Ideally, a child’s bike should be less than 40% of their weight, but often this is not possible. When choosing the right bike for your child, seek out the lightest bike you can find in your price range.
Weight, however, should never be looked at in isolation. Many cheap big-box-store bikes are similar in weight to higher-end bikes, but weigh less due to their too-small frames and lack of hand brakes. Decreasing the weight on a child’s bike is a priority for well-designed bikes, so higher-end kids’ bike companies proudly display their bikes’ weights, while most major bike companies refrain from publishing them.
3. What is the best frame design for kids bikes?
A child’s body position on the bike plays a large role in how well they can ride the bike. Like cars, bikes with a high center-of-gravity and a short wheelbase (distance wheel to wheel) are going to lose their balance and tip over more easily. When designed correctly, bikes with a longer wheelbase provide more stability and control for the rider. Handlebar placement contributes to the overall maneuverability of the bike and comfort of the rider.
BALANCING FEATURES (COCKPIT AND WHEELBASE):
For beginning riders, bikes with a lower overall center-of-gravity tend to be easier for kids to balance and maintain balancing (especially since they often ride at slower speeds). These bikes generally have lower minimum seat heights and longer frames (wheelbases) than other bikes with the same tire size. The easiest way to determine the difference in wheelbases between two kids’ bikes is to look at the amount of space between the seat and the handlebars (called the cockpit of a bike). The Huffy Rock It 12″ has a significantly shorter wheelbase and smaller cockpit than the Islabikes CNOC 14 Large.
A smaller cockpit provides less room for the rider and can cause kids’ knees to hit the handlebars when turning. The shape of the handlebars can also minimize the cockpit and significantly affect the maneuverability of a bike. Tall handlebars that sweep back, often found on big-box-store bikes, limit the rider’s space and prevent them from applying more force on the handlebars. This is especially important for beginning riders. Being able to lean in towards their handlebars helps them get in a better position to begin pedaling as well as get more leverage on the handlebars.
On the contrary, handlebars that are too low place beginning riders in a really aggressive position, which can cause them to tire out more easily as well as put strain on their neck. For more adventurous riders, a more aggressive position can be beneficial, but for the average young child rider, a mid-rise handlebar is ideal. For experienced older riders, the shape of the handlebars best for them depends on the type of riding they want to do, but for the average rider, low-rise to mid-rise is best.
4. What are the best types of brakes for kids’ bikes?
A child’s bike is only as good as its brakes. All bikes are required to have brakes, but the overall quality and performance of brakes vary greatly. High-end bikes generally have responsive dual handbrakes that are easy to activate, while lower-end bikes generally only have a coaster brake. The pros and cons of various systems are outlined below, but before you place a child on a bike, it is essential that they know how to stop it.
Coaster brakes (back-pedal brakes) are the standard on most 12″ to 16″ bikes as they are cheaper and essentially maintenance free, but they can be a headache for kids learning how to pedal. Kids naturally pedal backward on a bike when they start to lose their balance, or when riding uphill. On a freewheel bike (a bike without a coaster), backpedaling helps kids regain their balance and allows them to keep riding.
On a bike with a coaster brake, backpedaling causes unexpected stops, leading to falls and also delaying a child from mastering pedaling. For experienced riders, coaster brakes can cause them to lose all their momentum when riding uphill. As a result, we recommend freewheel bikes for beginning and experienced riders, BUT they can be expensive and hard to come by. In fact, coaster brakes are required by the CPSC on most 12″ and 14″ kids’ bikes, but not on 16″ and up.
Around the age of 3.5, kids have enough hand-eye coordination to use a properly designed hand brake. Hand brakes are generally more efficient and much more intuitive than coaster brakes, but they aren’t without their downfalls. Hand brakes do require maintenance and the vast majority of hand brakes on kids’ bikes, especially those on lower-end bikes, are poorly designed.
Hard to reach and hard to activate, most of these brakes are not designed for kids’ smaller and weaker hands. To test whether a hand brake is easy to use, pull the brake lever with your pinky finger. If the brake is hard to activate with your pinky, you can try to adjust the brake lever, but more than likely the brake is poorly-designed and will be a challenge for your child to use. Kids should NOT have to slam on their brakes to stop.
On the contrary, well-designed brakes are very responsive and when activated, easily stop a bike with minimal efforts by the child. Designed with small reach levers, that are much closer to the handlebar grips than standard levers; well-designed brakes are easier to activate and easier to pull. In fact, when riding a high-end bike for the first time, we highly recommend having kids walk the bike before riding it to help get a feel for the proper amount of pressure needed to stop the bike (which is usually much less than they anticipate).
It is also important to note whether the hand brakes activate the front or rear tire. While unlikely on small 12″ to 16″ bikes, kids on larger 20″ and 24″ bikes can endo (fly over the handlebars) if they brake only on the front tire. Upon doing so, the front tire of their bike will quickly stop, causing the rear tire to come off the ground, creating the potential to go flying over the handlebars. In the U.S., it is standard for the right-hand brake to activate the rear tire and the left brake the front. As a result, it is vital to teach kids to brake with BOTH their hands or with just their right.
SPECIALTY HAND BRAKES
To prevent potential injuries from braking (going over the handlebars), Guardian Bikes created a unique SureStop system that allows both front and rear brakes to be activated with one pull on the right brake lever. Currently only available on 16″, 20″ and 24″ bikes, more information about their unique system can also be found in our Guardian 20″ bike review. WOOM bikes also developed a clever solution for improving safety. Young kids often get confused between their left and right, so WOOM bikes made their right-hand brake lever green to remind kids which brake lever to use. To prevent the possibility of endos, Pello Bikes only includes a rear hand brake, as well as a coaster, on their 14″ and 16″ models (read our Pello bike review).
5. Do I need to worry about the gearing of a bike (gain ratio)?
Single Speed Bikes
The gain ratio of a bike determines how easy it is to start pedaling a bike as well as how fast you can get going on the bike. Gain ratios are only a concern for single-speed bikes. Bikes with gears, generally only on 20″ and up, have multiple gears to choose from. Single-speed bikes, essentially all 12″ to 16″ bikes, only have one.
Gain ratio is number calculated using the wheel size, crank arm length (the pedal arm length), and the number of teeth on the front and rear cogs. A high gain ratio requires more effort to get started but allows the bike to travel further with every pedal (like a high gear on an adult bike). A low gain ratio requires less effort to get the bike started but requires more “pedal spinning” to get the bike going (like a low gear on an adult bike). Then older and/or stronger a child, the higher the gain ratio they will be comfortable riding.
The differences between the gain ratios of kids’ bikes is slight, but does make a difference in the ride-ability of a bike. Lower gain ratios, like a 3.02 on the WOOM3, are better for timid kids or those who plan on riding up hills. Higher gain ratios, like a 4.5 on the Dimensions 16, are best for eager kids who are ready to muscle their way up hills or quickly gain speed on flat surfaces. Gain Ratios are NOT provided by any bike manufacturer, but we have calculated many for you and have them listed in our Kids’ Bikes: Product Filter Tool.
Bikes with Gears
Gears and shifters are available on some 20″ bikes and most 24″ bikes. The components on a geared bike add weight to a bike, often require maintenance, and can be hard for a child to use. As a result, we recommend only getting a bike with gears if your child truly plans on using them. The average neighborhood bike rider does not need gears, while a child going on a long bike ride or on a ride with great changes in elevation would benefit from being able to shift gears with speed and elevation changes.
6. What makes a bike easier to ride (q-factor)?
The Q-factor of a bike is the distance between the inside edges of the pedals. If the pedals on a bike are far apart, kids have to splay their legs out to pedal, which is inefficient and often uncomfortable. When pedals are close together, kids can pedal without splay, providing an easier and more efficient pedal stroke. The smaller or younger a child is, the more important the Q-factor is.
Petite kids and/or younger kids with smaller frames benefit the most from a narrow Q-factor. Many kids’ bikes have wide Q-factors because they are built with adult bike components, as they are readily available and cheaper to produce. Due to the specialty parts required to create a kids’ bike with a narrow Q-factor, they are generally only found on higher-end brands such as Islabikes, WOOM, Pello and Frog. We have yet to find a budget bike with a narrow Q-factor. Q-factors are rarely provided by bike manufacturers, but we have many listed in our Kids’ Bikes: Product Filter Tool.
7. How much should I spend on a kids’ bike?
In the end, price (and your budget) is going to dictate your decision quite significantly. More expensive bikes are almost always going to perform better than cheaper bikes, BUT as long as it is safe, any bike is better than no bike. Buy the best bike you can afford. Do not be discouraged if you can’t afford the top rated bikes on this site, but also be patient with your child when learning to ride on a less-than-ideal bike. More often than not, a bike’s geometry and design cause more delays in mastering a pedal bike than a child’s effort.
If your budget is tight, always consider buying used. The first kid’s bike we ever bought was an old Specialized Hotrock we got off of Craigslist for $30. It took a lot of elbow grease to get it up and running, but once we did it lasted our kids for several years. Also, be mindful that kids outgrow their bikes within a year or two, but purchasing a larger bike that they will grow into will likely only delay their ability to truly master and/or enjoy riding.
Which bike is best for your child?
Now that you know what to look for, head over to our Kids’ Bikes Product Filter Tool for help finding the bike that best matches your desired features, your child’s age and size, and your budget.
- The New and Better Kids Bike Sizing Guide: An easy-to-understand infographic breaking down kids bike sizing
- Why You Should Never Buy a 12″ Bike (with a few exceptions): The problems with 12″ bikes.
- Best 16″ Kids’ Bikes: A comparison of over 20 different 16″ pedal bikes.
- Best 20″ Kids’ Bikes: A comparison of over 15 different 20″ pedal bikes.
- Best 24″ Kids’ Bikes: Our quick list of our favorite bikes for kids 8 to 11-years-old