Today whilst driving, in a place I am not normally in, I saw a streetside ad (Nationwide Autos I think) saying "Tyres Inflated With Nitrogen Here" or something similar but definately Nitrogen!! What's all that about, anybody know??
Cheers
John
They probably say that oxygen-free tyres make the in-car sound better.... ;-)
Apparently nitrogen does not leak through the tyre walls as quickly as oxygen and stops oxidisation of the insudes of the tyres prolonging their life. Done on aircraft where tyres are retreaded and the carcass needs a long life. Prob. a complete waste of time on a car.
It could be just air. Even an ordinary pump puts nitrogen in the tyre. It's just that there's some oxygen as well. Bet it doesn't say '100% nitrogen'. You could have some fun and ask.
Peter Scott
Since the partial pressure of oxygen inside the nitrogen inflated tyre is 0 Pa, the oxygen in the atmosphere passes through the oxygen-permeable walls of the tyre, leaking into the tyre, despite the
2 or 3 bar adverse total-pressure difference. After some time, you would still get a nitrogen/oxygen mixture in the tyre, although it should remain stable.It is the same mechanism that allows oxygen to leak through the walls of pressurized, non-barrier, plastic heating pipes, causing corrosion of the ferrous components in the system.
and the same mechanism which allows air to leak in to pressurised sealed heating systems through any tiny water leaks, even though the heating system is 1 bar more than atmospheric pressure.
LOL Bob that is brilliant - made me smile - you should post it on one of the audio groups about the OFC cable mobs
Regards, Mike
The theory is that nitrogen has larger molecules than other constituents of air, so will retain the correct pressure longer. And that the oxygen present in air attacks the 'rubber' of the tyre.
But I'd guess most little used tyres - like say on a caravan - will suffer more from sunlight than oxygen damage. And that all car tyres will be worn out long before it becomes a problem.
Just to add it's common practice in commercial aircraft tyres - I'm told.
Seems to be common practice in a certain tyre fitters round here. Quote you a nice cheap price for the tyre then add £4/tyre for the gas inside. Won't be using them again.
I suppose it is easy to think of air as being free - but it must cost heck of a lot to buy and legally maintain a Compressor. I wonder if some fitters are finding more economical to use nitrogen than air - but profiteer from it because it is 'different' and will appeal to some?
It's the obvious explanation. Good tyres on good wheels simply don't lose pressure these days. You're likely to lose more in the act of checking them - which you'd still have to do with nitrogen.
And as regards damage to the rubber, the tyres on my SD1 are far older than most would have due to the low annual mileage and even wear you get with a RWD. But still hold air perfectly adequately on a good wheel.
Could be on an aircraft that smoking the tyres at every landing - and that they are subsequently re-moulded - has some bearing on the use of nitrogen. But neither really applies to the average car.
I have a V reg landrover defender, 45000 miles from new, and I have never pumped up any of its tyres, and they are still going strong and still have plenty of tread.
Possibly its a better feeling to have anintert gas that can't support combustion.
spot on.
i used to work in aerospace industry and that is the reason that nitrogen is used. brake fluid is hydraulic oil which will burn, so makes sense to use an inert gas for the tyres, as they can get very hot on a bad landing from the multiple disks. if there was a tyre explosion, due to heat, the an awful lot of oxygen would be made available to the fire.
sorry for lack of caps, i'm holding a very nice bit of piazza in my left hand as i type
dave
The Natural Philosopher wrote in news:crj5tm$6bv$3$ snipped-for-privacy@news.demon.co.uk:
Last time I got a tyre, must be at least 18 months ago, they used nitrogen. I tend to agree with the 'cheaper than cleaning the compressed air' theory
- certainly I wasn't charged anything extra for it (and competitive for the tyre). They also offer to top up the tyres they fit (for free) if ever you need it.
But rather than the nitrogen issue, the biggest improvement seemed to me that they used proper torque wrenches to tighten the wheel nuts. Couldn't help wondering how many wheels had fallen off after being over-tightened?
It was somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave" saying something like:
Aye, the surrounding air being seriously low in it.
Nice marble?
But did they look up and adjust the torque wrench before using it? Last time I saw a fast fit place use one, it was handed from one person to another working on different cars and used without adjustment. Of course they could have had the same torque setting and the operator knew this. But there again...
Probably very few, compared to those that have been under tightened by 'want-ta-be' mechanics or helpless owners.....
Yes.20% at 1 bar, compared to 20% at maybe 10 bar? Not sure what aircraft tyres are inflated to, but its pretty high.
I can see the point.
Wheel nuts are nearly alway *over* tightened in my experience, both by 'professional' tyre fitters when they use pneumatic spanners and by car owners when they use a spanner and jump on the end 'just to make sure'.
In reality even somewhat under tightened (i.e. less than the specified torque figure) nuts will be fine. In my very many years of removing and replacing wheels on all sorts of vehicles I've only once had a wheel come loose and that was when I hadn't tightened the nuts at all, only put them on loosely by hand. There was no harm done, it was very obvious that there was something wrong long before the wheel was anywhere near actually coming off.
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