Someone kindly posted this picture from a 1913 catalog a while back. I thought I'd print out a paper copy to take to Bakersfield to help identify original caps.
Upon looking at the picture more closely, it appears that the original cap is larger than the two more modern caps on each side. Is that really true that the original caps are distinctly larger, or is it just an optical illusion in this picture ?
Don't forget that dust caps go over them, so they don't show. I leave them off to reduce excess weight.
Well, yeah, I know they don't show. But it's sort of like when your mother told you not to wear ratty old underwear because you might be in an accident on the way to school. (Still don't understand that one.)
What if you have a flat and while you are repairing it alongside the road some pious yuppie in a Prius stops to help you? So, he says, "Say mister, isn't that the wrong type valve stem cap you have there?"
Now, wouldn't THAT be embarrassing?
Agree, valve stems need their caps, my mommy wouldn't let me go out in the winter w/o my cap and mittens
As for the caps, look for 'Schrader' brand marked on the cap base, and a fine vertical knurl, with the top split valve core wrench. You know that little valve core wrench comes in handy, and its on each of the caps!
The modern rubber caps or modern Schrader caps in aluminum , even if they have the valve core wrench aren't as correct as the one shown in this old adv.
Four or five (if the car has a spare tire) caps with the notch for removing valve cores is redundant.
Only one inner tube on the car needs a cap with the notched valve remover. The rest of the caps on the car can be the plain variety (i.e. if you need to remove a valve core, you only need one tool with the car, not four or five).
It's a good idea to have caps on all the valves.
Note that both the plain and notched metal caps have a rubber gasket inside. There is a reason for this. The cap serves as insurance against a leaky valve core. (I recently picked up some brand new Schrader plain metal caps and they are still include the rubber gasket.)
If you really want to get anal on this subject, you should read the information the Model A boys have. They have it down to a science!