<VV> Tire life

[Jay Maechtlen]

On 1/27/2020 2:24 AM, Hugo Miller via VirtualVairs wrote:
> 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.
>
Well, the sales pitch is that Nitrogen reduces tire aging.

But filling once with air isn't a big deal.

Filling repeatedly with 50% oxygen might be...


>
> 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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-- 
Jay Maechtlen
SoCal
'61 2-dr modified w/fiberglass skin,
transverse 3.8 Buick V6 TH440T4 trans