A 20-inch bike with training wheels is built for children roughly 6 to 9 years old, though size depends more on inseam and riding confidence than age alone

A 20-inch wheel diameter is the standard size for this stage because it bridges the gap between smaller 16-inch bikes and adult 24-inch models. The wheel size refers to the diameter of the tire, measured in inches. Training wheels (also called stabilizer wheels) bolt to the rear axle and keep the bike upright while a child learns to pedal, steer, and balance separately.

The frame itself is usually steel or aluminum, and the bike typically weighs between 25 and 35 pounds. Most come with hand brakes, coaster brakes (where you pedal backward to stop), or both. The seat height is adjustable on most models, which matters because a child should be able to touch the ground with their toes while seated — this is the single most important fit measurement.

Training wheels are temporary. They come off once a child can balance and pedal together, usually within weeks or months. Some bikes ship with training wheels included; others sell them separately. Removing them is straightforward — two bolts per wheel — and the bike becomes a standard 20-inch model that a child can ride without stabilizers.

Key Takeaways

  • A 20-inch bike fits children whose inseam is roughly 18 to 22 inches, which usually means ages 6 to 9, but measure your child's inseam before buying.
  • Training wheels should be removable bolts, not welded or glued, so you can take them off once your child no longer needs them.
  • Seat height is the most critical fit measurement — your child should touch the ground with their toes while seated, not their full foot or just their heel.
  • Hand brakes and coaster brakes each have trade-offs: hand brakes teach the skill your child will use on adult bikes, but coaster brakes are simpler for younger riders.
  • Most 20-inch bikes with training wheels cost between $100 and $250 new, depending on frame material and brake type.

How to measure your child for the right frame size

The most reliable measurement is inseam, not age or height. Have your child stand barefoot with their back against a wall, then measure from the floor to the inside of their thigh (where the leg meets the body). A 20-inch bike typically fits an inseam of 18 to 22 inches. If your child's inseam is under 18 inches, a 16-inch bike may be more appropriate; over 22 inches, a 24-inch model might work better.

Once you have a candidate bike, have your child sit on the seat with the pedal at its lowest point. Their leg should be nearly straight but not locked — there should be a slight bend at the knee. The seat should be high enough that your child can pedal efficiently but low enough that they can touch the ground with their toes when seated upright. If the seat cannot be adjusted low enough, the frame is too large.

Reach is a secondary concern. Your child should be able to grip the handlebars comfortably without stretching or hunching. If the reach feels too long, the child may tire quickly or develop poor posture. Most 20-inch bikes have adjustable stem heights (the part that holds the handlebars), so some reach issues can be corrected after purchase.

Training wheels: removable design and adjustment

Training wheels should attach to the rear axle with bolts that you can remove with a wrench — usually a 10mm or 12mm socket. Avoid bikes where the training wheels are welded, glued, or otherwise permanent, because you will not be able to take them off without damaging the frame or paying a mechanic.

Most training wheels sit slightly higher than the rear tire when the bike is upright, so they only touch the ground if the bike tilts. As your child gains balance, you can gradually raise the training wheels so they barely graze the pavement. This teaches the child to balance without suddenly removing the wheels entirely. Some training wheels have a screw adjustment for this; others require you to unbolt and reposition them.

Training wheels add weight and drag, so they slow the bike down slightly and make pedaling a little harder. This is intentional — it gives a child time to react and learn. Once removed, the bike will feel noticeably faster and more responsive, which is why the transition to riding without them can feel like a step up.

Brake types and what each one teaches

Coaster brakes work by pedaling backward. They are straightforward, require no hand coordination, and cannot fail due to cable stretch or rust. A child learning to ride often focuses hard on pedaling forward, so coaster brakes mean they do not have to think about a separate braking action. The downside is that coaster brakes do not work if the pedals are not moving, and they teach a braking method that adult bikes do not use.

Hand brakes (usually rim brakes or V-brakes on this size bike) require the child to squeeze a lever with their fingers while pedaling. This is more complex at first, but it is the braking method used on nearly all adult bikes. A child who learns hand brakes on a 20-inch bike will not have to relearn braking when they move to a larger bike. Hand brakes also work regardless of pedal position, which is safer in an emergency.

Many 20-inch bikes come with both — a coaster brake and hand brakes on the front wheel, or hand brakes on both wheels with a coaster as backup. This gives a child options and lets them learn hand braking at their own pace. If you are choosing between the two, consider whether your child will ride mostly in your yard (coaster is fine) or on streets and paths where they need to brake while coasting (hand brakes are better).

Frame material: steel versus aluminum

Steel frames are heavier, more durable, and less expensive. A steel 20-inch bike typically weighs 28 to 35 pounds. Steel resists dents and can be repaired by a welder if bent. Steel frames are common on bikes under $150 and are a solid choice if the bike will be ridden hard or shared among siblings.

Aluminum frames are lighter, usually 24 to 28 pounds, and do not rust. They are stiffer than steel, which means the bike feels more responsive but also transmits more vibration from bumps. Aluminum cannot be welded easily, so a bent aluminum frame usually means replacement rather than repair. Aluminum bikes typically cost $150 to $250.

For a child learning to ride, the weight difference matters. A lighter bike is easier to maneuver and less tiring to pedal. However, a heavier steel bike is more forgiving if the child crashes or tips over. If your child is small or tires easily, aluminum is worth the extra cost. If durability and cost are priorities, steel is the practical choice.

Accessories and safety gear to consider separately

Most 20-inch bikes ship with pedals, grips, and a seat, but they often do not include a helmet, lights, or reflectors. A helmet is essential — it should fit snugly on your child's head without tilting forward or backward, and the straps should form a V under the chin. Helmets are not expensive and can prevent serious injury.

Reflectors and lights are useful if your child will ride near dusk or in low light. Many bikes come with reflectors on the wheels and pedals, but front and rear lights (battery-powered or rechargeable) make the bike visible to cars. A bell or horn is not required but helps your child alert pedestrians.

Kickstands are helpful for parking but add weight and can catch on clothing or obstacles. Some bikes include them; others do not. Training wheels themselves act as a parking aid, so a kickstand is less critical on a bike with stabilizers.

Common issues and how to prevent them

Training wheels that are too high or too low will either not support the bike or will prevent your child from learning to balance. Check the adjustment regularly — as your child grows or as the bike settles, the wheels may need repositioning. If the training wheels are dragging constantly, raise them slightly so they only touch when the bike tilts.

Seat slippage is common on cheaper bikes. If the seat keeps sliding forward or backward, tighten the seat post clamp (the bolt that holds the seat to the frame) with an Allen wrench. Check it every few weeks, especially if the bike is ridden frequently.

Flat tires happen, but they are preventable. Keep the tires inflated to the pressure printed on the tire sidewall — usually 40 to 65 PSI on a 20-inch bike. Check pressure monthly. If a tire does go flat, most bike shops can patch or replace it for $10 to $25.

Chain rust and noise are signs that the chain needs cleaning and lubrication. Wipe the chain with a dry cloth and explore bike-specific chain lube (not WD-40) every month or after riding in wet conditions. A rusty chain will eventually break, so maintenance is worth the five minutes it takes.

When to remove training wheels and what to expect

Most children are ready to ride without training wheels once they can pedal smoothly, steer without wobbling, and stay upright for at least a few seconds. This usually happens within a few weeks of regular riding, though some children take longer. There is no rush — training wheels are not a failure, and removing them before your child is ready can be frustrating for both of you.

When you do remove the training wheels, lower the seat slightly so your child's feet can touch the ground more easily. This gives them confidence and a way to catch themselves if they start to fall. Have them practice in an open, flat area — a parking lot or empty field — rather than on a street or path with obstacles.

The first few rides without training wheels will feel wobbly and uncertain. Your child may need you to hold the seat or run alongside. This is normal. Most children find their balance within a few rides and quickly forget they ever needed training wheels. Once they do, the training wheels can be stored or removed permanently.

Frequently Asked Questions

What is the difference between a 20-inch bike and a 24-inch bike?

A 24-inch bike has larger wheels and a longer frame, fitting children with inseams over 22 inches (usually ages 9 and up). The larger wheels roll faster and handle rougher terrain better, but they are harder to control for a child still learning. If your child is between sizes, measure their inseam and choose based on that rather than age.

Can I use training wheels on a bike that did not come with them?

Yes. Universal training wheels bolt onto the rear axle of most 20-inch bikes and cost $20 to $40. Make sure the axle is the right diameter (usually 3/8 inch) and that the training wheels are rated for the bike's weight. Installation takes about 10 minutes with a wrench.

How long do training wheels usually last?

Training wheels wear out slowly because they do not bear the full weight of the bike — the rear tire does most of the work. They typically last several years of regular use. If the wheels become flat or the bolts rust, replacement wheels cost $15 to $30.

Should I buy a bike that is too big so my child can grow into it?

No. A bike that is too large is harder to control, more tiring to pedal, and more likely to cause crashes. Your child will outgrow a properly fitted 20-inch bike within a few years, but that is normal. A bike that fits now is safer and more fun to ride than one they will fit into later.

What should I do if my child is afraid to ride?

Start in a safe, flat area with no traffic or obstacles. Let them get used to sitting on the seat and pushing with their feet before pedaling. Ride alongside them or hold the seat for the first few rides. Fear usually fades once they realize the training wheels will keep them upright. Patience and practice matter more than speed.