Child Cycle Sizing

Question
My 6 year old son (4 feet tall) just completed a 50 mile bike ride on his little bike.  We're trying to get him a new bike as a prize, but we're struggling to figure the correct size and type of bike to get.  He wants one with gears, and finding that for his height is not the most common.  We've heard that it's important to have just a tiny bit of bend in the leg when the foot is on the pedal, we've also heard that the toes should be able to touch the ground when sitting on the seat, and it doesn't seem like you can have both. Of course, there are also the differences of coaster brakes vs hand brakes, and the longer bike where you lean over vs the shorter bike where you sit up straighter.  Currently he uses the bike mostly for riding around our house (dirt/grass), though he also rides on paved roads for a few miles at times.  This isn't for racing or anything professional, just enjoyment.  What is more important to consider for sizing a child's bike?

Answer
Well the real consideration here what type of riding he will be doing. If he wants a "mountain" type bike with knobby tires, then a lower seat is OK. If he wants a "road" type bike (with thin tires, drop handlebars, etc.) then the slight bend in the knee is the proper measurement.

At 6 years old, he's still growing. So I probablly wouldn't spend too much, since he will outgrow it soon.

Forget coaster brakes, any bike that still has them is really a toy.

If he is going to do a lot of dirt/grass riding, then I would go with a mountain type. You can get some decent ones, even at dept stores for under $200. If he really starts riding more on paved roads, then you can look at upgrading to a road bike.

Hope this helps
Scott<>