A friend of mine son is 9 and his weight is 125 and she wants to get him a mountain bike for christmas?

What size should she get. Can she still get a childrens bike

It is not really based upon weight as much as it is upon height. I would say she should get a bigger bike for him as long as he is tall enough for it

It isn't based on weight, but height. He needs a bike that he can pedal comfortably while sitting on the seat.
Don't get a childs bike, get a 26" wheel with a frame size that fits 13" or 15" seat tube size., Go to the bike shop to get the right fit.
i would recommend getting a 20" with a small frame. the weight doesnt really matter, its the hight and inseam (the length of the inside of his leg) if you want to get a good fit, then measure his leg from the bottom of the foot to just below the hips. get a bike with a frame that is about 2" less than the length of his leg. this way, he can stand over the bike with at least 2" of clearance.

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Kids Bike Schwinn Bike Cruiser Bike Road Bike Folding Bike Mountain Bike

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