Originally Posted by
motobecane69
Presta valve stems are metal so evenif they move around a bit they shouldn't get damaged which is why I think many people report not putting anything in the valve hole and not having problems. OF the people that do put something in the valve hole, it's probably a case of rather being safe than sorry. I would think once the tire is inflated, it's pushing against the tire, it's not going to move around a whole lot or get caught up in the valve hole but I suppose it's possible.
Yes, it is possible. In fact, I've had something similar happen to me. When I built the wheels for my touring bike, I decided to try using Velocity's VeloPlugs rather than rim tape. The notable problem with this system is that there is no protection around the hole where the valve stem goes through the rim. Sure enough, every tube that I installed developed a leak near the base of the valve stem within short order.
A good cloth rim tape will help prevent problems like these... but it's still not a bad idea to install a shim or grommet. Let me tell you from experience: successfully patching a hole near the base of the valve stem is not easy.