Arguably the least important part on any bike is the inner tube valve stem cap. It doesn’t hold in air. It does keep water and dust and grime and such out of the valve. Although, if you’ve got Presta valves, they’re pretty well sealed off by that little screw down plunger nut. And I don’t see this as even a slight issue no matter what kind of valve you’re running.
I noticed/realized something comical the other day when I was preparing Humble Horse for a ride up Brown Mountain. HH is my “good” mountain bike, the one with shocks and disk brakes and fanciness. I use it exclusively for dirty work up on the mountain. And yet it’s the only one of my bikes (n+1) that has no valve stem caps.
If I don’t need caps on HH then why in the world would I need them on T80’s or MM or SSSS… Well, I don’t, but I guess as long as they’re already on there I’m not going to leave them off the next time I pump.
And actually, now that I think about it, some of those caps do have a purpose. The inner tubes I’ve been buying recently from my LBS have, for some reason, yellow valve stem caps. I’ve grown to like these. They look especially sharp on Purple People Eater as they set off his yellow lettering. And they’re on the Mule, too, because even though she’s not the snappiest dresser I do like her to get some attention here and there.
An additional plus to the yellow caps is that they’re easier to find. It seems like, so often when I’m pumping my tires, the valve stem temporarily eludes my eyes. They seem to hide out tucked just inside the brake calipers or behind a seat-stay.
Plus, once you set down a black valve stem cap on the ground you can pretty much forget about ever finding it again. But not yellow! It’s all making sense to me now. Le cap jaune.