Tire valve caps must be of metal construction?

solo

Member
[FONT=&quot] [/FONT][FONT=&quot]Tire[/FONT][FONT=&quot] valve caps must be of metal construction?

I just read that in prep of a motorcycle for racing, and for the life of me, I can't see why?
It makes more sense to me that they be of plastic, due to if they ever fell off, that they most likely wouldn't go through a tire.

Could someone please tell me why they have to be metal, and does it matter if they are gold plated? Cause I have some really nice good plated tire valve caps that most likely would make me go faster on the track... well, maybe make me look like I'm going faster..lol
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Juan42

Active Member
I don't know this for absolute fact, however I suspect that a good quality metal cap with a rubber sealing ring inside has a better chance of holding pressure in the case of an internal valve stem leak than a plastic cap would.
 

solo

Member
I don't know this for absolute fact, however I suspect that a good quality metal cap with a rubber sealing ring inside has a better chance of holding pressure in the case of an internal valve stem leak than a plastic cap would.

That does sort of make sense, but a good plastic cap should do the same thing. I wonder if a person was to use shrink tubing over the metal cap if that could also help in preventing a possible puncture, if the cap worked its way off and onto the track.
 

jetfixer15

Active Member
Juan is absolutely correct. A metal valve stem cap will grip the metal valve stem threads better than a plastic one, giving it a much better ability to hold air in the tire in case of valve faliure or leakage. Many metal valve stem caps also have a rubber ring inside that provides even a better air seal in the event of faliure. A lot of metal valve stem caps are rated to a maximum PSI retention value for tire valves, dependant on their intended use. I have never seen a metal valve stem cap puncture a tire. We use them in aviation, and it's not an issue there at all, and have never seen them loosen themsleves off if properly installed in the first place.
 

solo

Member
Juan is absolutely correct. A metal valve stem cap will grip the metal valve stem threads better than a plastic one, giving it a much better ability to hold air in the tire in case of valve faliure or leakage. Many metal valve stem caps also have a rubber ring inside that provides even a better air seal in the event of faliure. A lot of metal valve stem caps are rated to a maximum PSI retention value for tire valves, dependant on their intended use. I have never seen a metal valve stem cap puncture a tire. We use them in aviation, and it's not an issue there at all, and have never seen them loosen themsleves off if properly installed in the first place.

Well, rules are rules.. so on go the gold valve caps... man I'm gonna fly now..lol
Thanks!
 

Tinker

New Member
I'm not sure how accurate this is, but I was told that in some cases, depending on valve stem spring quality and tension, it is possible that sheer centrifical force can sometimes be enough to over come a faulty stem spring and at high speed, the valve stem actually opens and the metal valve cap is capable of being turned onto the valve stem at a higher torque than plastic thereby ensuring a tighter seal.
 
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