Hello all, I have a 20 month old son who has always been very mobile and my wife and I have been thinking about getting him one of those 12" bikes with training wheels. We also see the tricycles but I would like him to have something for him to grow into. My question is when did you begin to have your child ride a bicycle? is it an age thing, height thing, or just when we feel comfortable? just looking for others experiences with this. Thanks!