I recently read an article (I don't remember where) that said valve caps are necessary for schrader valves because dirt and dust can foul the mechanism, but caps aren't necessary on presta valves because they seal themselves when screwed down properly. I use caps so the presta valves don't rip my jersey when I fix a flat and take the bad tube home for repair or disposal. I also think it looks better, but that's just me.

Shipping regulations?

Where have you been?

This is a great idea, however, the first couple of times I cut the end off they didn't work, you have to cut it and then test it, if it doesn't work try cutting a tiny bit more off the end, I wasted a cap trying to make it work, not a big deal, but you can't just cut it and think it's good to go unless you get lucky. There are two problems with doing this, the first problem is that you have to have a press on style pump instead of screw on, press on you find at gas stations so not much of a problem; the second issue in my case was that it worked only one time, after that it wouldn't work, not sure why. So I got tired of playing with it, so for $1 I went and got the one made of aluminum (they also come in brass) and it's threaded. The only reason I carry it is in case my rubber Presta seal on my pump fails due to wearing out, then I can just reverse the rubber seal and use it as a Schrader pump, screw on the adapter to the Presta valve and pump away.

Yes, that is true, the valve core in a Schrader is subject to damage and or clogging due to dirt and water, and that crap can also make the valve leak if you don't keep the valve cap on.

Now there is possible same situation with the Presta as well, but most people do not use the cap because those valve just don't seem to care as much as Schrader does, like I said earlier if you're going to be in a wet and or muddy environment you should use the presta cap, and the schrader cap. Most roadies don't ride in the rain so most roadies ditch the presta caps, but my touring bike came with Presta valves so on that bike I use the cap, but not on my regular bikes.

I ride in the rain and snow and never had a problem from not having a cap on.

More of a problem is the tire sealant making the valve stick and clogging the pump head.

I would rather be safe than sorry, and the weight of a cap is so slight I can't even feel the weight in my hand, so I'm not bothered by the weight of it.

Its not the weight,if it was i'd put light weight water in my bidon and helium in my tires.

Presta caps a t!ts on a bull. They serve no purpose.

Yes this is true, Some brands of Prest tube have screw in valves just like Schraders, be sure and check this out before throwing away what is a good tube.

Just use a different spoke color:
P1030026 on Flickr

Personally, I find the presta valve to be a homely little device, so even if the cap isn’t really needed, and it isn’t, my preference is to cover it up.
Tim