Just to keep the "nitrogen in racing tires" debate going a little further...here are some snippets I pulled from various web sites dealing with racing. The primary reason seems to be that the water vapor in air is what causes the most expansion as tire temperature rises. For other applications, such as air in tires with steel rims and perhaps also inside things like shock absorbers and struts, it avoids oxidation problems. Tom ====== Kiekhaefer, an eccentric German and the genius behind the Mercury Outboard Motor dynasty, had burst onto the NASCAR scene in 1955, using the sport as a tool to market his outboard motors. A perfectionist like the sport had never seen, Kiekhaefer revolutionized what until then had been strictly a shade-tree mechanics' sport, instituting such sweeping innovations as team transporters and extensive testing as well as seemingly innocuous improvements like using paper air filters and filling tires with nitrogen to maintain air pressure. === We have switched to nitrogen when inflating the tires. Unlike air, nitrogen contains almost no moisture, so heat does not cause the tires to expand like those filled with air. This allows us to maintain more control of tire sizes. ====== Use nitrogen to fill your tires, it has a much higher expansion rate. It will not expand under greater heat generated by track temperatures and friction created by a tire burn-out. This keeps the tire from growing, allowing for a better foot print and more consistent times. =============== > There is a reason nitrogen is better than air. I'm told the problem with > air in tires is that the water vapor in it expands drastically when > heated, causing a big change in tire pressures as the tires heat up.(I've > seen it change by 4 lbs during a single lap in an autocross.) Bottled So it's not the nitrogen, but the water vapor? Air of course is 79% Nitrogen, 20% Oxygen and 1% trace gasses. The pressure in a tire increases 1 psi for every 10 degrees outside temp (tire carcass or ambient air temp) from what I've heard (I've never done the calcs for that one Mac) regardless of the minor difference represented by the 20% oxygen. Thus Matt R correctly referred to the ideal gas law. > nitrogen is dry, and expands very little when heated, therefore the tire > pressures are much more stable. It's also a very inert gas, so it doesn't > rot the tires. I'll go along with that. The 20% oxygen is probably slightly more active than the if it were another 20% nitrogen. ==== Q. I always hear about problems associated with pressure build-up in the tires, and expensive gadgets to prevent this, like bleeder valves. Why don't they just use an inert gas like nitrogen? A. Everybody uses nitrogen in their tires. There is still pressure built up by heat when the race track meets the tire, but it is not as much as regular air. === By the way, race-car and aircraft tires often are filled with nitrogen, which is inert. An added bonus of this, of course, is that when the tires blow, they don't add "fuel," i.e., oxygen, to the fire, so to speak. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Tom Dittrich wrote: > > Just to keep the "nitrogen in racing tires" debate going a little > further...here are some snippets I pulled from various web sites dealing > with racing. The primary reason seems to be that the water vapor in air > is what causes the most expansion as tire temperature rises. For other > applications, such as air in tires with steel rims and perhaps also > inside things like shock absorbers and struts, it avoids oxidation > problems. > > Tom Well, it's probably about time to kill this thread. It is "off topic," after all. I read all the snippets, Tom, and as far as I know there were only two valid points: 1. O2 in tires will add a (miniscule) amount of O2 to any fire, and may accelerate degradation of the metallic parts inside tires (rims, etc.). I can't believe either of these is a significant reason for avoiding DRY air for inflation. 2. The snippets claim water VAPOR will expand more than any other common inflation gas (i.e., N2 or O2). That's wrong. Probably, racers avoid compressed air right out of the compressor because it likely contains misted water LIQUID (unlike DRY N2 from a tank). And, yes, those water droplets, as they convert to water VAPOR at racing temperatures, will lead to a greater pressure increase than if they were introduced as vapor. That COULD be significant, liquid water has a volume roughly 1800 times smaller than water vapor (same mas of H2O). 'Spect I'm done with this, though I enjoyed the contributions, and Tom's explained where the N2 mythology for racers began. I expect if I could corner the market on argon and get a similar myth going on its superiority to N2 (argon atoms are round, after all, and so they should not resist tire motion as they ricochet off the insides of tires, unlike oblong N2 molecules), I could retire on the profits! -- Dave Kruger Astoria, OR sea kayaker/chemist/one-time motorhead *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Tom: Now THAT makes sense. It's the water which has condensed that would make for the expansion. The water vapor is just another "ideal" gas. Thanks for bringing some light to this. Robert >The primary reason seems to be that the water vapor in air >is what causes the most expansion as tire temperature rises *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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