A 20-inch bike with training wheels is a pedal bike designed for children roughly 6 to 9 years old, with two small wheels mounted on the rear axle to prevent tipping
The "20 inches" refers to the diameter of the main wheels, measured from edge to edge across the center. Training wheels (also called stabilizer wheels) attach to the back of the bike frame and touch the ground alongside the rear tire, keeping the bike upright while a child learns to pedal and steer. Most 20-inch bikes with training wheels are steel-framed, weigh between 30 and 40 pounds, and come partially assembled — you typically need to attach the handlebars, seat, pedals, and training wheels yourself before the bike is ready to ride.
This size sits between smaller 16-inch bikes (for ages 4 to 6) and larger 24-inch bikes (for ages 9 and up). A child's inseam measurement is more reliable than age alone: if their inseam is roughly 18 to 22 inches, a 20-inch bike is usually the right fit. Training wheels let a child focus on pedaling and steering without worrying about balance, and most can be removed or adjusted as the child gains confidence.
Key Takeaways
- A 20-inch bike with training wheels fits children with an inseam of roughly 18 to 22 inches, typically ages 6 to 9.
- Training wheels prevent the bike from tipping sideways, allowing a child to learn pedaling and steering before learning balance.
- Most bikes arrive partially assembled and require you to attach handlebars, seat, pedals, and training wheels before use.
- Training wheels can usually be adjusted higher as a child gains confidence, or removed entirely once balance improves.
- Steel frames are standard and durable; lighter aluminum frames cost more but are easier for children to handle.
How to measure your child for the right frame size
The most accurate way to check fit is to have your child stand over the bike frame with both feet flat on the ground. There should be 1 to 2 inches of clearance between the child's crotch and the top tube (the horizontal bar running from the seat to the handlebars). If the child is standing on their tiptoes or if there is more than 2 inches of space, the frame is too large or too small.
Measure your child's inseam by having them stand barefoot with their back against a wall, then measure from the floor to the inside of their thigh where it meets the hip. A 20-inch bike typically suits inseams of 18 to 22 inches. If your child's inseam is closer to 16 inches, a 16-inch bike may be more comfortable; if it is closer to 24 inches, a 24-inch bike may be better. Seat height should be adjustable so that when the child sits on the seat with the pedal at its lowest point, their leg is almost straight but not locked at the knee.
What comes in the box and what assembly is required
A typical 20-inch bike with training wheels arrives with the frame, wheels, handlebars, seat, pedals, and training wheels as separate components or partially attached. You will need to attach the handlebars to the steering column (usually with an Allen wrench or Phillips screwdriver), slide the seat post into the frame and tighten it to the correct height, screw the pedals into the crank arms (note that the left pedal has a reverse thread), and bolt the training wheels to the rear axle on both sides.
Most manufacturers include an instruction booklet with diagrams showing each step. If the booklet is missing, the manufacturer's website usually has a PDF version. Assembly typically takes 30 to 60 minutes with basic tools: an adjustable wrench or socket set, Allen wrenches (usually 4mm, 5mm, and 6mm), a Phillips and flathead screwdriver, and sometimes a crank puller if the pedals are stuck. Do not overtighten bolts, especially on plastic components like the seat clamp, as this can crack them.
Training wheels: how they work and when to remove them
Training wheels are small wheels (typically 4 to 6 inches in diameter) mounted on brackets that bolt to the rear axle. They sit slightly higher than the main rear wheel initially, so the bike's weight rests on the rear tire and the training wheels only touch down if the bike tips sideways. As a child gains balance, you can adjust the training wheel brackets upward so the training wheels barely touch the ground — this forces the child to balance more while still preventing a complete tip-over.
Most children can begin riding without training wheels once they can pedal smoothly, steer without wobbling, and stay upright for 20 to 30 seconds without adult support. This usually happens between ages 6 and 8, though every child is different. To remove training wheels, unbolt the brackets from the rear axle (usually two bolts per side) and store them in case the child needs them again. Some parents remove one training wheel first to let the child adjust to partial balance before removing both.
Training wheels do not teach balance the way riding without them does, so a child who has only ever ridden with training wheels may struggle when they are removed. Many parents find it helpful to practice in a flat, open space like a parking lot or park, with an adult running alongside to catch the bike if needed.
Steel versus aluminum frames and what each costs
Most 20-inch bikes with training wheels have steel frames, which are heavier but less expensive and very durable. A steel-frame 20-inch bike typically costs between $80 and $150. Steel frames can rust if left outside in wet weather, so storing the bike indoors or under a cover extends its life. Steel is forgiving if the bike is dropped or crashed, and repairs are usually straightforward.
Aluminum frames are lighter (often 5 to 10 pounds less than steel) and do not rust, making them easier for a child to handle and better for long-term outdoor storage. Aluminum 20-inch bikes typically cost between $150 and $250. The lighter weight can make a difference for a smaller or less confident child, but it is not necessary for most riders. Aluminum frames are also more prone to bending in a crash, though they rarely break completely.
For a child learning to ride, a steel frame is usually the better choice because cost is lower, durability is high, and the extra weight is not significant enough to prevent learning. If the child is particularly small or will be riding frequently, aluminum may be worth the extra cost.
Brakes, pedals, and other features to compare
Most 20-inch bikes with training wheels use one of two brake types: coaster brakes (you pedal backward to brake) or hand brakes (you squeeze levers on the handlebars). Coaster brakes are simpler and require no maintenance, but they do not work if the pedals are not moving — a child cannot brake while coasting. Hand brakes give more control and work while coasting, but they require more hand strength and coordination. Many entry-level bikes use coaster brakes; mid-range bikes often have hand brakes on the front wheel and a coaster brake on the rear.
Pedals on children's bikes are usually plastic with rubber grips. Some bikes have pedals with reflectors or cages to keep feet from slipping. Toe clips (small cages that surround the pedal) are less common on 20-inch bikes but can help keep a child's foot in the right position. Handlebars should be padded or wrapped in foam to reduce injury if the child falls forward.
Tires are typically solid rubber or pneumatic (air-filled). Pneumatic tires provide a smoother ride and are easier to pedal, but they can puncture and need occasional air. Solid rubber tires are maintenance-free but provide a rougher ride. Most 20-inch bikes use pneumatic tires because the smoother ride encourages children to ride more.
Maintenance and storage tips for a 20-inch bike
Check the tire pressure every two to four weeks if the bike has pneumatic tires. The correct pressure is printed on the tire sidewall (usually between 30 and 50 PSI for a 20-inch bike). Underinflated tires make pedaling harder and are more prone to pinch flats; overinflated tires provide a harsh ride and can burst. Use a floor pump with a pressure gauge for accuracy.
Wipe the chain with a dry cloth after riding in wet conditions, and explore chain lubricant (a light oil designed for bikes) every month or after riding in rain. A dry, rusty chain makes pedaling harder and wears out faster. Check that the training wheels are still bolted securely before each ride, especially if the bike has been stored for a while.
Store the bike indoors or under a cover to protect it from rust and UV damage. If the bike will be stored for more than a few months, deflate the tires slightly (to about 80% of normal pressure) to reduce stress on the tubes. Before bringing the bike back out, re-inflate the tires and spin the wheels to make sure nothing is stuck or bent.
Frequently Asked Questions
Can I use a 20-inch bike without training wheels from the start?
Yes, but it is much harder. A child learning to ride needs to focus on pedaling and steering first; balance comes later. Training wheels remove the balance challenge, letting a child build confidence with pedaling and steering. Most children find it easier to learn with training wheels and transition to riding without them once they are comfortable.
How long do training wheels usually last?
Training wheels typically last two to four years of regular use before the axles wear out or the wheels become flat-spotted (worn unevenly). If the bike is used only occasionally or stored indoors, they may last longer. Replacement training wheel sets cost $20 to $40 and are available from most bike shops or online retailers.
What if my child is between sizes — should I buy a 16-inch or 20-inch bike?
Measure the inseam first. If it is between 16 and 18 inches, a 16-inch bike is the safer choice because the child will have better control and confidence. A bike that is too large is harder to mount, steer, and stop. A child can outgrow a 16-inch bike in one to two years, but it is better to buy the right size now and upgrade later than to buy too large and risk discouraging the child from riding.
Do I need to buy safety gear along with the bike?
A helmet is the most important piece of safety gear and should be worn every time the child rides. Helmets cost $20 to $60 and should fit snugly without moving when the child shakes their head. Wrist guards, elbow pads, and knee pads are optional but can reduce scrapes and bruises during falls, especially for a child who is nervous about riding.
Can training wheels be adjusted or do they need to be removed all at once?
Most training wheel brackets can be adjusted upward by loosening the bolts and sliding the wheels higher on the mounting brackets. Raising them gradually forces the child to balance more while still providing a safety net. Some children transition better with one wheel removed first, then both removed once they are confident with partial balance.