My son rides a POS transformer bike that is holding him backfor any kind of distane it feels like it weighes as much as my GT MTB. I woul like to get him a BMX 20" bike but the frame will need to be very small. Any help will be appreciated. I do not mind building the bike or piecing one together but I need help where to start. It might be a used bike or new I have no idea.
Visit a LBS that sells used bikes, craigslist, and e-bay.
I found a used trek jet for $60 in good condition, far lighter then walmart/target jobs and a bit cheaper.
The seatpost is about 4-5" above the seat tube, should fit an average 5 y/o standover wise, the top tube might be a little long.
The Lil Ripper is awsome!!! I would get him a 16" again but he basically needs more gear and a lighter bike. The Transformer bike his Aunt got him is killing him but he still goes 4+ miles but he pedals so fast and if he stops pedaling its like an auto brake is ingaged!
I just got a used Kona Makena for my 5 year old, it is about 10 pounds lighter than his previous "bike". I was looking for a trek or specialized bike for him. All of these have aluminum frames and reasonable components.