Originally Posted By: CapriRacer
Originally Posted By: Ducked
......I might do some crude “bench” testing with bits of tyre and / or inner tube.
First, innertubes are made with different types of rubbers than tires. Do a search and you'll find there are many types of rubbers and they have different properties - and react differently to chemicals - oil being one of them…
Well, sure. I don’t imagine that any testing I might do would be remotely definitive, but if I test inner tube with veg oil and it disintegrates that’ll be more worrying than if it doesn’t. Tyre sidewalls are relatively robust and are going to be difficult or impossible for me to “bench” test on useful timescales.
Originally Posted By: CapriRacer
Oh and John Baldwin's paper? There has been much discussion in the tire world about oxidation and the breakdown of the rubber over time - and John's paper was just one of the points of interest. The discussion has centered around that fact that the Law Partial Pressure of Gas indicates that the use of nitrogen as an inflation medium only results in changing the rate of oxidation by 50% - and that oxidation doesn't seem to be the deciding factor.
Tests have not established a good link between nitrogen inflation and tire durability.
So the idea the nitrogen inflation has some benefits for tire longevity doesn't have experimental support.
Well, I have to say your general conclusion doesn’t match the research reports I’ve seen, though they may not represent the concensus of opinion, if there is one. I looked on your website but could only find a mention of a single unpublished study.
I know this is a controversial area, with large vested interests, and a history of legal dispute. (If truth is the first casuality of war, it probably doesn’t survive boot-camp where there is litigation).
Much of the research I’ve seen comes from reports produced by, with or for the (US) National Highway Traffic Safety Agency. I don’t necessarily take them as an unimpeachable source, but I doubt they have any commercial interest in promoting nitrogen tyre filling.
They are of the opinion that internal oxidation is a (in fact, according to the NHTSA, the) main cause of tyre age-related failure, and that measures to prevent this oxidation will reduce the effect of tyre ageing. I've quoted experimental research above (Baldwin, 2004) that supports this for nitrogen filling and for butyl rubber linings, but I have seen other references Sperberg (1967); Tokita (1985), Karmarker, (2006) to studies supporting the importance of oxidative ageing and a protective role for nitrogen. These studies (which I havn't read in the original) generally seem to involve accelerated aging tests with different gas fills.
I get that oxygen is going to diffuse into the tyre, and there is apparently an optimum purity of N filling beyond which this oxygen diffusion increases. Nevertheless, according to Dawes (2010) [these are essentially the same paper]
http://www.moderntiredealer.com/files/st...ktires-daws.pdf
http://www.dawsengineering.com/linked_files/practicalaspectsofnitrogentireinflation-daws.pdf
the tyres lifetime exposure to oxygen is significantly reduced (by about 50% over its lifetime) by N filling even with air top off. If N is used to top-off or re-inflate the tyre, the reduction is greater.
This is of mostly academic interest to me since I'm not currently using N inflation, but I'm told its cheap/free here in Taiwan, so I may start, especially if/when I get new tyres.
If it wasn't cheap/free, I might look into CO2 inflation. CO2 is not as inert as N, but its pretty inert, and it could probably be simply and cheaply arranged with some yeast and sugar. AFAIK there's no data available on its protective effect, if any.
Baldwin, J.M., Bauer, D.R., and Ellwood, K.R., “Effects of Nitrogen Inflation on Tire Aging
and Performance”, presented at a meeting of the Rubber Division, American Chemical Society,
Grand Rapids, MI, May 17-19, 2004.
Sperberg, L.R., “Tire Durability with Nitrogen Inflation”, Rubber Age, 99(11), 83 (1967).
Karmarker, U., “Effect of Nitrogen Purity on the Oxidation of Belt Coat Compound”, Presented
at a Meeting of the International Tire Exhibition and Conference (ITEC), Akron, OH, September,
2006, Paper No. 19B.
Tokita, N., et al., “Long Term Durability of Tires”, International Rubber Conference
Proceedings”, Kyoto, Japan, October 15-18, 1985, Paper 18D17, pp. 672-679.