Hello Welcome to the forums. I agree with Homebrew check your local bike shop (BS), we used to have these great serrated or knurled washers for mounting freestyle pegs and cases just like yours.
What kind of bike is it? Does it have a coaster brake or hand brakes? is the coaster connected correctly?
Also if he is strong enough to keep pulling the wheel loose consider signing him for a Junior track racing.
http://www.niagaracycle.com/product_...ducts_id=34309
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk
Last edited by Bianchigirll; 05-01-12 at 06:34 AM.