Kids grow so if they are in a child seat or trailer it won't be long until they outgrow it. At 2-4 years they can move on to their own appropriately sized tri-cycle. On a bicycle, kids can experience/learn the laws of inertia, pedaling, steering, braking and sitting on a saddle. Trikes don't do much to develop a sense of balance and they can be tippy (excluding low-lying "big wheels").
Most kids try a two-wheeler with training wheels around age 3 years.
Between the ages of 4 and 8 years most kids have developed sufficient physical coordination and agility, good balance, and master starting and stopping on a tricycle or training wheels so that they are ready to learn to ride a bicycle. (Note: Kids generally lack the coordination and strength for hand brakes until at least 5.) But, along with physical skills it also takes mental readiness (self-confidence) and motivation to learn to bicycle. Some kids don't develop this until they are 10 or more years old. It sometimes takes a lot of patience on the part of parents. Interest and readiness to learn to ride a bike can manifests itself as questions about bicycles, a desire to ride with friends, talk about tricycles and training wheels as things for "babies," etc. For tips on how to teach a kid to learn to bicycle click on this link.
Guide to Kid Bike Sizes: Children's bike sizes are determined by wheel diameter, not seat height and frame size as is the case with adult bicycles. The chart below should help you narrow your search, but it is not a substitute for an expert helping you find a bike that is most suitable. A critical factor is the brakes. Coaster brakes tend to be easier for young kids to use but they become less common as the bikes get bigger. It can be a conundrum and dangerous when kids who are tall for their age fit bigger bikes with hand brakes that they can't operate well. After kids outgrow children's bikes they'll move into small-framed adult bikes with 26 inch, 27 inch or 700c wheels, which are sized by the length of the seat tube.
| Approximate Age | Child's Inseam | Wheel diameter "bike size" * | Comments: |
| 2-4 years | 14-17 inches 35-42 cm | 12 inches | Most come with training wheels, some are direct drive |
| 4-6 years | 16-20 inches 40-50 cm | 14 inches | not commonly available |
| 5-8 years | 18-22 inches 45-55 cm | 16 inches | Most have rear coaster breaks and pneumatic tires, some have front hand brakes. |
| 6-9 years | 20-24 inches 50-60 cm | 18 inches | not commonly available |
| 7-10 years | 22-25 inches 55-63 cm | 20 inches | Some models are multi-speed with hand brakes. |
| 9+ years | 24-28 inches 60-72 cm | 24 inches | Can have most of the feature of adult bikes. |
Note: the highest rate of bike-related head injuries is among boys 10-14 years old. For more information on helmets go to www.ibike.org/education/helmet.htm.
Children under 12 years going solo on a tri-cycle or bicycle have a very limited range and don't get as much pleasure from simply cycling. If you want to have a family outing with more cycling, as you child outgrows their child seat (age 3) or trailer (age 4), there are a couple of options to consider: tandems with kid-kits on the rear seat and third wheel kid's seats. But you will still need destinations and activities that appeal to them. Whether by tandem or third wheel, your children will be right with you no matter how fast you ride. On a conventional tandem both cyclists have to pedal together, so when the adult pedals the child will have to pedal, unless they take their feet off the pedals. The third-wheel cycles are designed to be free wheeling so the child can sit back and enjoy the ride anytime they want. For links to equipment providers go to our link section and click on "technology & innovation".
To know more details read- http://www.ibike.org/education/buying.htm
