New to BMX, need help getting bike for son
My 9 year-old son wants to race BMX. Last year, before I knew he wanted to race, I bought him a GT Mach One Pro based on what the LBS guy told me, to "grow into". Riding around the neighborhood, it's fine. But my son is small for his age, and after watching him ride his bike at the local track (Chandler BMX), it's apparent that the bike is way too big for him. He looks strained riding it, and after a few laps, his back hurts. He's all of 4'3", 54 lbs.
His skill level is Novice, so I don't want to buy a $400+ bike at this point, but I do want to get him on something that fits right. Problem is, I don't know what "right" is, and after the last LBS selling me a too-big bike for him, I'm not too trusting of the shop guy who just wants to move a bike that day. If anyone can recommend a good shop and someone knowledgeable to talk to in the Chandler/Phx, Az area, that would be great.
Can I make this bike fit him with a different stem/handlebar setup? Is it worth the effort/expense? Any advice or pointers to stuff already written on the subject of fitting a rider to a BMX bike would be much appreciated.