Tricycle 

• Miniature-size bike with three wheels is perfect for the smallest cyclists.
• Help a child learn the basic mechanics of riding a bike with the added safety and comfort of three wheels for extra balance.
• Perfect for children ages 2-4.
• A child from 28 to 38 inches tall or with a 14-17 inch inseam will need the smallest 12-inch wheel size.
• Average cost: $50

With Training Wheels 

• These are slightly bigger and some have removable training wheels. All have rear coaster brakes. Some have a hand brake. They are great because they grow with your child as he or she learns to ride a bike.
• For children ages 4-6.
• A child 38 to 48 inches tall with an 18-21 inch inseam will need 16" wheels.
• Average cost: $75+

Mountain Bike 

• Once your child has gotten a bit bigger they will need a bike with more adult features, more gear speeds, hand brakes, and a kick stand.
• For 7-8 year olds (48 to 60 inches tall) stick to the 20" wheel models, and for 9 years and up go for the 24" models.
• Prices start at $100 but can go up to $300 or more.

BMX 

• They have a T-handlebar and usually only rear coaster brakes.
• No matter how big the child gets, a BMX bike can always have its charm, especially if he or she gets into extreme sports.
• There are three types: BMX racing  for normal kid stuff like riding around the block, BMX freestyle  with pegs and spinning handlebars for doing tricks, and BMX jumping bikes  with extra solid 48-spoke wheels.
• Prices range from about $150-$200.