who cares? i do this all the time, sometimes with a rubber grommet, sometimes without. I'd rather ride my bike than worry about what kind of valve stems it has. I also don't carry a pump, i carry a small flat kit with a few CO2 cartridges, a presta/schrader adapter, and a patch kit of a few sizes. I've only had to walk home (closer than the nearest LBS) once, knock on wood.