As we all know, kids grow fast so buying a bike for them is not the easy for their parents.Childrens bikes generally fall into one of a number of different size categories which are based on their size and age. For toddlers ages 3-6, a 12-inch bike is recommended. Kids between the ages of 7 and 12 can pick from either 14-inch or 16-inch bikes depending on how tall, strong and skilled they are. Once you've determined the look and size of the bike, it's time to think about what kind of bike your kid needs. If he or she is going to be riding out in the countryside or on unpaved roads, you're going to need to select a bike with more rugged, chunkier tyres with a deeper tread that will hold up to a lot of abuse.