While listening to the radio the other day, a scientific discussion among motoring experts (alright, it was a factoid on Steve Wright in The Afternoon) advanced the opinion that tyres should be completely deflated every two years as the air in them had absorbed moisture and woud cause the tyre to degrade, thus shortening the life.
Any truth in that, or is it cobblers?
|
Their is probably something in it from a technical angle, but I dare say that it would take many many years for this to happen, and much longer than the time span of what 99.9% of people keep the same tyres on their vehicle.
I would have thought sunlight would do more harm to the rubber than the air inside being moist.
|
|
Tractor tyres are sometimes filled with water to increase weight for better traction, does not do them any damage. Dont think damp air would harm car tyres.
|
Assumes the tyres were inflated in the rain I think! Tyres for serious racing are inflated with dry nitrogen but it is done here to limit the change of pressure with temperature. Principal of a steam engine etc and you get a big rise in pressure as the tyre temperature go up.
Demon Tweaks used to offer it, and I think some others did/do, but I've not been looking lately.
|
Assumes the tyres were inflated in the rain I think! Tyres for serious racing are inflated with dry nitrogen but it is done here to limit the change of pressure with temperature.
How does that work? Can Charles's law not be applied to a mixture of air and water? Is it to do with the water changing state? I thought the supposed reasons for using nitrogen were
- less pressure loss through permeation (N molecules are a bit bigger than O ones even though they are lighter)
- no oxygen to react with and degrade the rubber
- no compressor oil in the gas which also reacts with rubber.
Water vapour aside (what remains of my A level physics can't cope with that complication) it seems to me that if you inflate your tyres with dry air using an oil free compressor then you should keep topping them up rather than fully exchanging the air. Why? Well, if the O leaks out faster than the N, then the concentration of N will gradually increase!
My tyres wear out first anyway!
I can't see why tyres would absorb water. Or do they mean an accumulation of H2O from top-up air? I must hold a cold mirror to my valve and loosen the core...
Edited by Manatee on 09/08/2008 at 10:08
|
>>I thought the supposedreasons for using nitrogen were *blah blah blah*
Twaddle. Absolute twaddle.
Racing cars and aviation has used Nitrogen in tyres for years, due to 1) the problems of any moisture in tyres actually freezing at 35 000 ft ; 2) racing tyres reaching high temperatures, causing the moisture to heat to a steaming point; and 3) in both instances, in the event of a crash, they don't want a few cubic meters of previously pressurised air adding to any conflaguration, should the tyre burst.
I've had Nitrogen in the tyres, has made no discernible differeence, and just costs a few bob.
Marketting hype, in my honest opinion.
|
>>I thought the supposed >> reasons for using nitrogen were >> *blah blah blah* Twaddle. Absolute twaddle.
Don't shoot the messenger - I was talking about road car tyres not racing cars and aeroplanes, and I did say supposed reasons...I have no problems using air.
The exam question is, should you change the air in your tyres? Personally I would put this, as a pastime, on a par with the stuffing of mushrooms - life's too short.
|
|
|
|
|
|
>>I would have thought sunlight would do more harm to the rubber than the air inside being moist.<<
I would agree. The 205 GTi which I have owned for the last two years came with the original (1989) Pirelli P600 unused on the spare, and I have put it into use as it shows no external cracking, having spent its life 'out of sight'. This may be against current thinking on tyres, and I suspect the rubber may have hardened slightly, but I have not detected any drawbacks so far. What is more, the pressure holds up fine, even on the Peugeot alloy.
|
I would agree. The 205 GTi which I have owned for the last two years came with the original (1989) Pirelli P600 unused on the spare and I have put it into use as it shows no external cracking having spent its life 'out of sight'.
Yes, my 1994 Mercedes has what appears to be the original unused spare wheel and tyre and both look pretty much as new. Not sure I'd use the tyre though.
|
Yes my 1994 Mercedes has what appears to be the original unused spare wheel and tyre and both look pretty much as new. Not sure I'd use the tyre though.
IIRC this was one of the reasons (read excuses) offered by the guys who tried to justify space savers... ie, too many drivers use over-age spares, which lead to blowouts, as opposed to fitting a space-saver, and getting the 'proper' tyre fixed poste haste.
Makes sense.
Unless you happen to suffer a puncture on Sunday afternnon, and face a 400km - at 80km/h - journey to the next spot in civilization which might possibly have a tyre fixing/replacement centre.
Try this on a Sunday afternoon in darkest africa.
|
IIRC this was one of the reasons (read excuses) offered by the guys who tried to justify space savers... ie too many drivers use over-age spares which lead to blowouts as opposed to fitting a space-saver and getting the 'proper' tyre fixed poste haste.
This thought occured to me the other day, so many people are so lazy with their cars that if not forced to fix their proper tyre then they would happily run around on the spare ad infinitum.
I passed an Octavia (I think) yesterday that was parked sporting one space saver spare and one very flat front tyre, I bet they wish they'd gotten their original puncture fixed more quickly! :-)
|
|
|
|
|
|
Surely the water or water vapour inside a tyre (& its notional effect) is insignifigant when compared against the water it encounters on the outside? If it really had such an effect you would expect tyres to rot many times faster from the outside, so any internal rot (or effect upon tyre life) is inconsequential.
|
Car tyres are lined with butyl (the same material as a pond liner) as it it better at keeping air inside that natural rubber.
Are you saying that a tyre inflated to 30 PSI and inserted into a bath of water will absorb the water before the air leaks out of the same microscopic holes?
I might invent a gadget that fits between the tyre inflator and the valve that filters any moisture from the air (the only way moisture can enter a tyre thats inflated to some degree), then I could go on The Dragons Den and chat with that nice ice cream man ;o)
|
|
I changed the tyres on my caravan last month for the first time in 36 years. The outsides were degraded by sunlight, but the insides were as bright and sound as new.
|
|
I thought air was 80% nitrogen anyway.
|
>>I thought air was 80% nitrogen anyway.<<
Quite, but cylinder nitrogen will be dry; air from the compressor won't.
Edited by Andrew-T on 09/08/2008 at 17:14
|
>>I thought air was 80% nitrogen anyway.<< Quite but cylinder nitrogen will be dry; air from the compressor won't.
BUT gas in the tyre will contain some air anyway, right?
Because even though you are pressurising the tyre, before you fill a tyre on the rim, there is an amount of air in it already...
Aviation and racing tyres use a recirculating filling system initially, AFAIK, to eliminate ALL traces of anything but nitrogen
|
|
|
|
>>..for the first time in 36 years.>>
Has the caravan survived as well as the tyres?
|
|
|
|
|
|
It's the latter.
|
|
Why does tyre air always smell of fish ?
|
|
Fish smell of urea. Only guessing but I wonder if uric acid is used at some stage of the tyre manufacturing process. Or is it simply that rubber smells a bit like fish ? Think I'm falling asle...............................................................
|
|
|
|
