Flat and Curved adhesive mounts are the key piece to mounting GoPro's securely on many things. This complete set includes 6 adhesive mounts with 3M adhesive backing. 3 curved and 3 flat. They are compatible with all Hero camera bodies.
On a bike, frames and helmets can both be a key spot for one of these mounts. One thing we have found is the more you get into using your GoPro, the more of these mounts you tend to go through. Stock up because you don't want to be out of them when you really need one.