On 5/16/2019 10:26 PM, Arlen G. Holder wrote:
Two minor questions that came up today when I was showing an inquisitive
teen how to mount & balance his own tires for the car he recently got for
free from a neighbor.

1. The teen asked me why this slit in the typical air chuck...
https://i.postimg.cc/43JN7rWw/valve02.jpg

2. The kid asked me what the practical difference was between choosing
between two air valves, one for up to 65 psi and the other up to 80 psi for
a typical 30 to 40psi nominal economy car tire such as his a
https://i.postimg.cc/76Z6cp7b/valve01.jpg

In both cases, I told the kid that I don't know the answers and that I'd
ask folks on this newsgroup who know more than I do about such things, so
I'll point the kid to this thread, when/if reasonable answers ensue.

I did hazard a guess that I suspect the slit in the chuck is perhaps to
"let air out", although I'm not sure why we'd want to do that except, I
guess, if we use the chuck as the air-release mechanism (similar to the
"nib" on the back of a typical pencil-type air pressure gauge).

Likewise, I told him that it doesn't seem to matter all that much which
pressure valve we use for his passenger car tires, AFAIK, where I like the
brass valve, which happens to handle higher pressure, but I didn't see that
it mattered for a passenger car, particularly since they were both
essentially the same price.

One happens to be a "bolt in" type while the other is "snap in", but I
didn't see that as a practical difference - do you, and one was slightly
shorter but only because O'Reillys didn't have the same lengths in stock
for the two types.

The specs on the back of the O'Reillys packages a

XtraSeal 15-4600 Tire Valves 1-1/4" HP 0.453" TR600HP
o Max cold inflation pressure is 80 psi
o Rim thickness not to exceed 0.205" (5.2mm)

XtraSeal 15-4142 Tire Valves 1-1/2" HP 0.453" TR414
o Max cold inflation pressure is 65 psi
o Rim thickness not to exceed 0.156" (3.96mm)

The slot is just like a slot in the head of a screw. It is used for
assembly, disassembly

The valve stem is for different rims. Typically truck rims are thicker
and heavier and tires have higher pressure.