Black and gray bikes:
Spiderman drag bikes, gutted to remove zip action
flick trix bike tire to fill gap in rear wheel

Green and Red/White bikes:
the corpse crotch rocket type bikes
rims, tires, disc brakes from diecast 1:18 bikes
nails for axles
wire jump rings and heat shrink
metal duct tape

When CCXIII got rolling it was announced that video games was the theme. I racked my brain, and it was difficult since I have done at least 2 video game theme projects for past CC's. Looking around in my parts stash I found some crotch rocket style bikes, and instantly thought about road rash. I played the sega version of road rash or maybe V2 until the moving background went blurry as a kid. Hours and hours of the intro to "rusty cage" and a 2 litre of Mt Dew piloting a seemingly stationary bike dodging all kinds of hazards.