Bugatti Veyron wheels? Mental.
Discussion
996TT02 said:
The majority of valve caps won't seal anything for any length of time. Hard plastic and brass pressed together by the maximum force that can be generated by means of a crummy and very fine plastic thread don't seal sweet f-a.
This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
You obviously feel very strongly about this - I don't and aren't really interested in arguing on the internet - only trying to promote and engage in healthy discussion on a motoring forum, occasionally venturing a view on something that I have experience of - or can be backed up independently.This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
http://www.michelin.co.uk/tyres/learn-share/care-g...
If it's wrong in your view, or it's wrong full stop, I can only reiterate it's what I have been told / taught / instructed over many years in this industry. It is validated above.
The diatribe about 'deserved condescension' from engineers and linking 'getting your hands dirty' to being the only way you can voice an opinion / share information is a bit much though...after all, you have no idea what experience I or any other poster has on this topic.
996TT02 said:
The majority of valve caps won't seal anything for any length of time. Hard plastic and brass pressed together by the maximum force that can be generated by means of a crummy and very fine plastic thread don't seal sweet f-a.
This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
Utter codswallop. This kind of garbage really annoys me.This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
A standard car or motorbike valve has an o-ring seal in the cap that seals against the valve tube. They can seal against enormous pressures.
Here, you've annoyed me so much I fished one out of my toolbox and took a picture just for you!
supersingle said:
996TT02 said:
The majority of valve caps won't seal anything for any length of time. Hard plastic and brass pressed together by the maximum force that can be generated by means of a crummy and very fine plastic thread don't seal sweet f-a.
This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
Utter codswallop. This kind of garbage really annoys me.This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
A standard car or motorbike valve has an o-ring seal in the cap that seals against the valve tube. They can seal against enormous pressures.
Here, you've annoyed me so much I fished one out of my toolbox and took a picture just for you!
AdeTuono said:
supersingle said:
996TT02 said:
The majority of valve caps won't seal anything for any length of time. Hard plastic and brass pressed together by the maximum force that can be generated by means of a crummy and very fine plastic thread don't seal sweet f-a.
This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
Utter codswallop. This kind of garbage really annoys me.This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
A standard car or motorbike valve has an o-ring seal in the cap that seals against the valve tube. They can seal against enormous pressures.
Here, you've annoyed me so much I fished one out of my toolbox and took a picture just for you!
Every post Max_Torque makes seems to go this way - interesting and informed post followed by a lot of pub expert "well *I* reckon" rubbish. FWIW I thought it was commonly known that the cap seals the valve but there you go.
dme123 said:
AdeTuono said:
supersingle said:
996TT02 said:
The majority of valve caps won't seal anything for any length of time. Hard plastic and brass pressed together by the maximum force that can be generated by means of a crummy and very fine plastic thread don't seal sweet f-a.
This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
Utter codswallop. This kind of garbage really annoys me.This isn't about cars or tyres, any person who actually gets their hands dirty doing whatever will call that theory what it really is. That a plastic valve cap as fitted to the majority of valves is not designed to seal is obvious for any of the above category of person that someone who thinks otherwise evidently is quite the opposite.
If you presented a common dust cap to an engineer as a design for a "seal" for anything you'd get all the condescending looks you'd deserve.
I and no doubt millions of people worldwide have run tyres for years without valve caps, speaking only for myself, I have never had tyres deflate for want of one.
I have no doubt that it is possible to design a valve cap that will seal - and some may well be capable of that - that's not the point, the point is that ordinarily the valve does the sealing and if it does not, then that valve needs replacing, trying to seal it with a dust cap is a bodge.
As for centrifugal force opening a valve, I don't know, certainly theoretically possible, the force keeping a valve closed at a given air pressure can be relatively easily determined knowing the diameter of the valve insert seal, and the centrifugal force the valve is subjected to at a certain radius and angular velocity, too, knowing the mass of this same valve insert, so if anyone is up to it they can do the measuring and maths and find out. I suspect that valve makers have this sussed out however.
A standard car or motorbike valve has an o-ring seal in the cap that seals against the valve tube. They can seal against enormous pressures.
Here, you've annoyed me so much I fished one out of my toolbox and took a picture just for you!
Every post Max_Torque makes seems to go this way - interesting and informed post followed by a lot of pub expert "well *I* reckon" rubbish. FWIW I thought it was commonly known that the cap seals the valve but there you go.
That seal in a plastic cap is there to seal moisture out, not air in.
Valve caps that are used as backup safety seals are generally steel or aluminium, with an o-ring in and a slit down the thread so any entrapped pressure will escape down the thread and not fire a valve cap into your eyeball at 300mph.
If you've ever taken an aluminium/steel cap off your air conditioning system, they are often this design, so are shock absorbers/dampers, I've got some in the car, I'll get a photo later.
99.9% of plastic passenger vehicle valve caps are not generally designed to keep air in, the thread engagement is so poor on most of them you'd be lucky if half of them could generate enough tension.
Valve caps that are used as backup safety seals are generally steel or aluminium, with an o-ring in and a slit down the thread so any entrapped pressure will escape down the thread and not fire a valve cap into your eyeball at 300mph.
If you've ever taken an aluminium/steel cap off your air conditioning system, they are often this design, so are shock absorbers/dampers, I've got some in the car, I'll get a photo later.
99.9% of plastic passenger vehicle valve caps are not generally designed to keep air in, the thread engagement is so poor on most of them you'd be lucky if half of them could generate enough tension.
Edited by PhillipM on Thursday 2nd April 22:15
PhillipM said:
That seal in a plastic cap is there to seal moisture out, not air in.
Valve caps that are used as backup safety seals are generally steel or aluminium, with an o-ring in and a slit down the thread so any entrapped pressure will escape down the thread and not fire a valve cap into your eyeball at 300mph.
If you've ever taken an aluminium/steel cap off your air conditioning system, they are often this design, so are shock absorbers/dampers, I've got some in the car, I'll get a photo later.
99.9% of plastic passenger vehicle valve caps are not generally designed to keep air in, the thread engagement is so poor on most of them you'd be lucky if half of them could generate enough tension.
Valve caps that are used as backup safety seals are generally steel or aluminium, with an o-ring in and a slit down the thread so any entrapped pressure will escape down the thread and not fire a valve cap into your eyeball at 300mph.
If you've ever taken an aluminium/steel cap off your air conditioning system, they are often this design, so are shock absorbers/dampers, I've got some in the car, I'll get a photo later.
99.9% of plastic passenger vehicle valve caps are not generally designed to keep air in, the thread engagement is so poor on most of them you'd be lucky if half of them could generate enough tension.
Edited by PhillipM on Thursday 2nd April 22:15
supersingle said:
I've thought of a destructive test that could easily be done to settle this (on the valve caps not the Veyron wheels )
I'm betting the cap can seal against 120psi from an air compressor. Any takers?
Do it, just to prove/disprove so that the Veyron's parts and service charges can be argued about instead.) I'm betting the cap can seal against 120psi from an air compressor. Any takers?
selym said:
supersingle said:
I've thought of a destructive test that could easily be done to settle this (on the valve caps not the Veyron wheels )
I'm betting the cap can seal against 120psi from an air compressor. Any takers?
Do it, just to prove/disprove so that the Veyron's parts and service charges can be argued about instead.) I'm betting the cap can seal against 120psi from an air compressor. Any takers?
kers.PhillipM said:
That seal in a plastic cap is there to seal moisture out, not air in.
Valve caps that are used as backup safety seals are generally steel or aluminium, with an o-ring in and a slit down the thread so any entrapped pressure will escape down the thread and not fire a valve cap into your eyeball at 300mph.
If you've ever taken an aluminium/steel cap off your air conditioning system, they are often this design, so are shock absorbers/dampers, I've got some in the car, I'll get a photo later.
99.9% of plastic passenger vehicle valve caps are not generally designed to keep air in, the thread engagement is so poor on most of them you'd be lucky if half of them could generate enough tension.
Valve caps that are used as backup safety seals are generally steel or aluminium, with an o-ring in and a slit down the thread so any entrapped pressure will escape down the thread and not fire a valve cap into your eyeball at 300mph.
If you've ever taken an aluminium/steel cap off your air conditioning system, they are often this design, so are shock absorbers/dampers, I've got some in the car, I'll get a photo later.
99.9% of plastic passenger vehicle valve caps are not generally designed to keep air in, the thread engagement is so poor on most of them you'd be lucky if half of them could generate enough tension.
Edited by PhillipM on Thursday 2nd April 22:15
From the link posted above
7.Tyre Valves
VALVES AND VALVE CAPS PROTECT YOU AND YOUR TYRES
Tyre valveValves and their components are ordinarily made of rubber, so they are subject to deterioration over time. Replacing them when you buy new tyres is an inexpensive way to protect your tyres, vehicle and yourself. At high speeds, a cracked, deteriorated rubber valve stem can bend from centrifugal force and allow air loss. The valve cap is also important. It’s the primary air seal and helps to keep out dust and dirt particles. You should check that your valves and valve caps are in good condition to:
Maintain an airtight seal
Maintain the correct tyre pressure
Ensure longer tyre life
I'm actually finding the Veyron talk (the justification for more expense *not* painting a carbon car specifically) *and* the valve talk quite interesting (I thought valve caps were for keeping the valve clean but the 'seal' guys have won me over). This thread is like a buy-one-get-one-free.
Does the Veyron have shiny metal (carbon?) valve caps with a logo or boring black plastic ones?
Does the Veyron have shiny metal (carbon?) valve caps with a logo or boring black plastic ones?
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