<VV> Tire life

Hugo Miller hugo at aruncoaches.co.uk
Mon Jan 27 05:24:16 EST 2020

Is that why they use nitrogen in tires today? To stop oxidisation? I 
thought it was because the molecules were bigger so the pressure stayed 
up longer, and apparently they are affected less by heat?
Boeing had a 747 explode once because it had been sitting on a very hot 
runway for hours with a nearly empty fuel tank, and there was a spark in 
the wiring inside the tank which set everything off. Their solution was 
ingenious, by "filtering" the air going into the tank. Only the oxygen 
atoms could get through, and they were thrown away, leaving the tank to 
fill with non-explosive nitrogen. I think I got tht the right way round 
re molecule size.

On 2020-01-27 06:24, Jay Maechtlen via VirtualVairs wrote:
> On 1/21/2020 5:32 PM, Bryan Blackwell via VirtualVairs wrote:
>> For those of you who wish to read further on tire life (in years), 
>> here are links to some studies on the subject from the folks who 
>> declared our Corvair safe:
>> NHTSA Tire Aging Test Development Project Phase 1:
>> https://one.nhtsa.gov/DOT/NHTSA/NRD/Multimedia/PDFs/Crash%20Avoidance/2009/811201.pdf
>> NHTSA Tire Aging Test Development Project Phase 2:
>> https://www.nhtsa.gov/DOT/NHTSA/NVS/Vehicle%20Research%20&%20Test%20Center%20(VRTC)/ca/capubs/811780.pdf
> The accelerated aging test is interesting - note what they did -
> "50 percent nitrogen gas and 50 percent oxygen gas (50%N2/50%O2) and
> aged in a circulating air oven for 3 or 5 weeks at 65°C. The fill gas
> was vented and refreshed weekly to maintain a sufficient supply of
> oxygen gas in the tire cavity to support oxidative aging."
> That is  50% oxygen in the tires - not the 21% of standard atmosphere
> - and vented and refreshed weekly to keep that percentage up.
> I don't see any references to actual tests of tires used on the road.
> I wonder how relevant this artificial aging of the inner tire is, 
> when
> in service the oxygen content of the air in the tire will drop as
> oxidation takes place.  The failures of the inner surface and between
> layers could be heavily influenced by this.
> If nothing else, don't run old tires underinflated or at the maximum
> rated loads for long periods of time!
> Jay
>> Personally in the DC area I go with 10 years from the sidewall date. 
>> Since our Corvairs don't get a lot of miles, choosing to change them 
>> by age rather than tread depth seems to make sense, and some of our 
>> other tires (winter, trailer, etc.) have the same issue.
>> BTW, if you don't know how to read date codes, I have a how to here:
>> http://autoxer.skiblack.com/tires.html#age
>> --Bryan
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