FYI bullet-proof vests aren't stab-proof.

I'm currently running a cheap Cheng Shin front tire with a Mr. Tuffy liner on my commuter. I've picked up glass, sharp rocks, even the side of a nail where the head - not the sharp end - embedded into the tire. No flats yet. My average cruising speed is 30 km/h (~20 MPH) so I'm not gently rolling over these objects, either.