Rock the late 70's track racing style of Breaking Away's protagonist Dave Stoller.
First, you need a properly outfitted red racing helmet. Any helmet and some red and white paint will do.
Next, you need the shirt. We just happen to have the Cutters shirt, made to spec, right down to Dave's racing number 34 on the back.
You can get one right here.
Then you'll need some black bike shorts. The shorter, the more authentic.
A little bit of blood on the shins really helps bring the whole costume together (and builds up your biker cred, to boot).
And finally, a pair of ratty converse or similar classic trainers; the dirtier and more beat-up the better.