Bugatti Veyron wheels? Mental.
Discussion
robinessex said:
The centrifugal force acts in an OUTWARD direction (obviously), so the centrifugal force on the valve core is ADDED to the force being applied to the valve core by the tyre pressure.
It isn't though, is it? The centrifugal force is subtracted from the tyre pressure force. The tendency will always be for the valve core to be flung to the outer diameter i.e. to open, overcoming tyre pressure.LukeR94 said:
Why? Surely every Bugatti Veyron owner isnt taking their car to 250+ every journey, so why would it matter?
No, but I was told by someone at the factory that Bugatti insist every Veyron should always be capable of reaching its maximum speed at any given time if required. I can tell you this much, I had a leaky valve on the dirt bike which I sealed with a metal cap c/w o-ring it held a pressure of 15 psi which is all I needed.
wiki sayeth :
Cap[edit]
A valve cap is important on a Schrader valve because if one is not fitted, dirt and water can enter the outside of the valve, potentially jamming it or contaminating the sealing surfaces and causing a leak. Rock salt and other chemical de-icers used in the winter are especially damaging for the brass components in the Schrader valve.[citation needed]
Some valve caps have a rubber-washer seal (or a synthetic-rubber-washer seal) inside to help make a hermetic seal (airtight seal). Such a rubber-washer-sealing-type cap also helps prevent air from escaping from a slightly leaking valve. In addition, the rubber washer prevents the cap from loosening and falling off due to vibrations and hence being lost, by acting as a cushion between the cap and the valve stem and in this way damping the vibrations
wiki sayeth :
Cap[edit]
A valve cap is important on a Schrader valve because if one is not fitted, dirt and water can enter the outside of the valve, potentially jamming it or contaminating the sealing surfaces and causing a leak. Rock salt and other chemical de-icers used in the winter are especially damaging for the brass components in the Schrader valve.[citation needed]
Some valve caps have a rubber-washer seal (or a synthetic-rubber-washer seal) inside to help make a hermetic seal (airtight seal). Such a rubber-washer-sealing-type cap also helps prevent air from escaping from a slightly leaking valve. In addition, the rubber washer prevents the cap from loosening and falling off due to vibrations and hence being lost, by acting as a cushion between the cap and the valve stem and in this way damping the vibrations
AdeTuono said:
robinessex said:
The centrifugal force acts in an OUTWARD direction (obviously), so the centrifugal force on the valve core is ADDED to the force being applied to the valve core by the tyre pressure.
It isn't though, is it? The centrifugal force is subtracted from the tyre pressure force. The tendency will always be for the valve core to be flung to the outer diameter i.e. to open, overcoming tyre pressure.braddo said:
This is interesting. 
Perhaps the pressure in your test rig will settle to something like, say, 50 psi - as long as the valve cap is an effective seal up to about 40-50 psi then that would always be sufficient to seal a car tyre, right?
Even a Veryron's at 250mph? Especially as the centrifugal force would be pushing the valve cap down onto the stem?
I tested the pressure this morning and it was down to 18psi. There's a leak and I don't think it matters how low the pressure goes, it'll continue to lose air until there's no pressure. The cap is made of stiff plastic, it's not like a rubbery inner tube which might seal up as the rubber contracts. Perhaps the pressure in your test rig will settle to something like, say, 50 psi - as long as the valve cap is an effective seal up to about 40-50 psi then that would always be sufficient to seal a car tyre, right? Even a Veryron's at 250mph? Especially as the centrifugal force would be pushing the valve cap down onto the stem?
I've got some metal caps on the way...
So after two days the pressure has gone down to 72psi. Holding the rig underwater reveals a tiny leak in one of my crappy welds. The cap itself is totally leak proof. Not bad for 7p. If you have a Veyron it's probably worth the investment in metal valve caps rather than trying to economise by using cheapo plastic items. 
Gibbo998 said:
DonkeyApple said:
It's become quite clear that 10p plastic dust caps are more interesting than a set of VW wheels. So why don't you jog on you stupid arse.
Your tag is quite appropriate...... A f
king complete donkey!supersingle said:
So after two days the pressure has gone down to 72psi. Holding the rig underwater reveals a tiny leak in one of my crappy welds. The cap itself is totally leak proof. Not bad for 7p.
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