We want to buy a bike for our 4yo, he's about 38 inches and doesn't know how to ride. What size should we get?

He should be able to touch the ground, preferably flat footed while seated for beginning riding. 16" will be too big (it's just a touch too big for my ds who is about 45"). 12" is probably what you'll need, possibly the rare, elusive 14" (not a common size in the States, but there is usually 1 boy style and maybe 2 girl styles).

This is a good link that goes through the sizes:

http://www.ibike.org/education/buying.htm

http://www.toysrus.com/product/index.jsp?productId=2408835&cp=2255961.2256573.2256592.2256602&parentPage=family

Does he like Diego? This is likely the only 14" boys bike available.

You might want to go to a store and try some out. They can vary a lot depending on the frame size (the size is the wheels, some have very short frames, others have big frames).

DS is 5 and about 43". He got a 16" bike last August and it fit him then (and still fits him great). His friend who just turned 4 in April got a 16" for his birthday and it fit him. DD also had a 16" bike when she was 4.

We just bought my daughter a bike for her birthday. She is only about 34-35" tall. We had tried her on different bicycles before to determine which size allowed her to reach the pedals without being too cramped. This time at the store though they had a little sign. You child stood next to it and it measured their inseam length and told you to use that for the size bike to buy. That measurement agreed with our thought and we got her a 10" bike.

oh, the elusive 14" :lol we couldn't find one that wasn't covered in Bratz or my little pony, etc. and they were all online.

dd has a 16" and it's tall for her (she's at least 42" tall) she's getting more comfortable on it but it's definitely big for her.

i absolutely recommend having him try a few sizes to see what he's most comfortable with. you want room to grow but not so big that it's scary!

My 4 yr. old is 43" and has been riding a 16" with training wheels since last summer. But I wish we would have bought a 12" because I know he'd be riding without training wheels if we had. He can't touch both feet flat to the ground on his bike. I bought it so it'd last a long time, but I have two kids, and it would have been worth it to buy a 12". I'll buy my littlest a 12" between 2.5 and 3.5.

How to test any style of bike for proper fit
a. Sitting on the seat with hands on the handlebar, your child must be able to place the balls of both feet on the ground.
b. Straddling the center bar, your child should be able to stand with both feet flat on the ground with about a 1-inch clearance between the crotch and the bar.
c. When buying a bike with hand brakes for an older child, make sure that the child can comfortably grasp the brakes and apply sufficient pressure to stop the bike

http://www.amazon.com/Radio-Flyer-Classic-Bicycle-Chain/dp/B00005A1LK/ref=sr_1_1/104-9422907-9961528?ie=UTF8&s=toys-and-games&qid=1180046029&sr=8-1

That is a pretty good quality 10" bike; I have one. It does not have brakes. I guess if he can put his feet down that would not matter. My son is 36" at 2.3 years old and he cannot put his feet down on this bike, but can pedal it well . The seat hight is actually the same as the seat height on a 12" bike I have for him. Have you looked at balance bikes as a first bike?

Another good bet might be this:

http://www.amazon.com/Schwinn-S6133-Roadster-10-Inch-Scooter/dp/B000IOQ0SY/ref=sr_1_8/104-9422907-9961528?ie=UTF8&s=toys-and-games&qid=1180046477&sr=8-8

My DS is 6 1/2, small for his age, and we just bought an 18 inch at TRU. He just learned to ride a 2 wheeler on a 16 inch and was a tad too small. I wanted him to get the next size before he got too comfortable on a bike he would grow out of soon.

We also bought a 12 inch for my 2 1/2 year old.

We pulled the bikes off the shelf to sit and size.

Trying some bikes out at the store would be the best way.

But I can say that all of my kids got a 16" bike when they were 4yo. A 12" bike would probably be too small- my kids got a 12" bike when they were 2yo.

Ds was about that size at age 4, we went with the 12".
He is very cautious and it took him a long time to get comfortable riding the tricycle, he wouldn't pedal it at all until he was 3.5. Even though he could.

He is still very cautious on his bike, and will probably have the training wheels on for a while yet. He is almost 5 and I'm glad we got the small size bike for him. If he was a more athletic, fearless type kid, I may have gone to a bigger size.

Ds1 is maybe 39 inches tall and my mom got him a 12 inch bike to ride at her house. He does great on it and really likes it. He will outgrow it soon, but ds2 will be able to use it next year. I had ds1 sit on a 16 inch bike in the store and he did fit on it, but he said it was too wobbly. The training wheels seemed to be a bit farther from the ground than on his 12 inch and it rocked back and forth. My dh wants to get him a bigger bike for our house. I think I'll have him try the 16 inch again sometime. He is really confident on the 12 inch and I'm glad we started with that.

We live in Massachusetts and I bought a 14" at Toys R Us! It was the absolute perfect size. It had no characters--there were a few designs and NONE had characters. The one we got was "fire power" design and made by Kent.