Nitrogen for street tires?
06-23-2006, 08:55 AM
#31
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I don't know if it is a correct assumption that these places that use so many air tools don't have an in-line moisture traps...even the ones that supply room air. I might swing by one today and find out. In any event, I think we are all in agreement that street tires derive little benefit from nitrogen, and that the benefit for track tires is probably minimal, and even that is debatable.
06-23-2006, 11:36 AM
#32
Rennlist Member
Originally Posted by JasonAndreas
FAA regulations require it to reduce fires hazards during landings caused by overheated rims.
“PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES 25.733 (e) For an airplane with a maximum certificated takeoff weight of more than 75,000 pounds, tires mounted on braked wheels must be inflated with dry nitrogen or other gases shown to be inert so that the gas mixture in the tire does not contain oxygen in excess of 5 percent by volume, unless it can be shown that the tire liner material will not produce a volatile gas when heated or that means are provided to prevent tire temperatures from reaching unsafe levels.”
Water vapor is still a gas and won't deviate that much from pv = nRT at the tire pressures we use. Even if the error was 5% (the maximum error rate listed in Marks' Standard Handbook for Mechanical Engineers) and the tire contained 1% water vapor you'd still be below the accuracy level of most tire gauges. Maybe in F1 where 1/8 PSI matters. But in this case Costco is not selling dry gas they are selling 95% nitrogen which as the Finn points out can be just as wet as air coming out of regular air compressor with an inline dryer.
Because it's a sales gimmick that is not free everywhere and the advertised reasons for using it don't past the smell test.
Its a convenient source of dry gas, that I can understand but any other reason...
"Pressure will increase or decrease to the same extent as the temperature increases or decreases regardless of which gas is in the tire."
“PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES 25.733 (e) For an airplane with a maximum certificated takeoff weight of more than 75,000 pounds, tires mounted on braked wheels must be inflated with dry nitrogen or other gases shown to be inert so that the gas mixture in the tire does not contain oxygen in excess of 5 percent by volume, unless it can be shown that the tire liner material will not produce a volatile gas when heated or that means are provided to prevent tire temperatures from reaching unsafe levels.”
Water vapor is still a gas and won't deviate that much from pv = nRT at the tire pressures we use. Even if the error was 5% (the maximum error rate listed in Marks' Standard Handbook for Mechanical Engineers) and the tire contained 1% water vapor you'd still be below the accuracy level of most tire gauges. Maybe in F1 where 1/8 PSI matters. But in this case Costco is not selling dry gas they are selling 95% nitrogen which as the Finn points out can be just as wet as air coming out of regular air compressor with an inline dryer.
Because it's a sales gimmick that is not free everywhere and the advertised reasons for using it don't past the smell test.
Its a convenient source of dry gas, that I can understand but any other reason...
"Pressure will increase or decrease to the same extent as the temperature increases or decreases regardless of which gas is in the tire."
Thank you for interjecting some science to this discussion. It was needed. 10 respect points to you, sir.
06-23-2006, 01:28 PM
#33
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so I was just thinking, how about pulling the core of the valve stem on one of these hydrogen filled tires, and lighting a match as the gas rushes out? that would be one cool flame thrower!
06-23-2006, 01:49 PM
#34
Rennlist Member
Here is the scoop...
There is a chap in SoCal that sells an "Octopus" device that connects all four tires to your nitrogen line. It then goes through a number of cycles where it fills and subsequently purges the tires of air. It costs about $350...I have not bought one yet.
The expense of nitrogen is not much at all, limited to purchasing a regulator with two gauges, one tells you the pressure inside the tank and the second shows the pressure are injecting into the tires. You will also need to purchase an an air inflation hose with the attachment for the valve stem. Total cost for this stuff was about $150. You will also need to refill the tank at about $20 a charge...you get lots of nitrogen for $20. The tank is on permanent loan.
What I do is pull the valve stem and let all the "free" air out. Next I purge the tire by filling with nitrogen and letting it out about 3 times. On the fourth inflation, I fill the tire to the recommended cold pressure.
Does this approach get all the "free" air out? Who knows. It seems to work for me. The other big benefit is the tank. I got a smaller one that is about 2 1/2 feet tall and about 10" in diameter. It hold a lot of nitrogen, thousands of pounds.
An finally, once you have the rig, that's it. No fuss, no muss. If you lug air to the track, the bottle and the regulator will fit into the trunk of a 993. I am hooked on nitrogen.
The expense of nitrogen is not much at all, limited to purchasing a regulator with two gauges, one tells you the pressure inside the tank and the second shows the pressure are injecting into the tires. You will also need to purchase an an air inflation hose with the attachment for the valve stem. Total cost for this stuff was about $150. You will also need to refill the tank at about $20 a charge...you get lots of nitrogen for $20. The tank is on permanent loan.
What I do is pull the valve stem and let all the "free" air out. Next I purge the tire by filling with nitrogen and letting it out about 3 times. On the fourth inflation, I fill the tire to the recommended cold pressure.
Does this approach get all the "free" air out? Who knows. It seems to work for me. The other big benefit is the tank. I got a smaller one that is about 2 1/2 feet tall and about 10" in diameter. It hold a lot of nitrogen, thousands of pounds.
An finally, once you have the rig, that's it. No fuss, no muss. If you lug air to the track, the bottle and the regulator will fit into the trunk of a 993. I am hooked on nitrogen.
06-23-2006, 03:19 PM
#35
Rennlist Member
all I know is from my kid's quarter midget racing experience...we'd set tire pressures based upon track conditions and weather. you want better grip, reduce the amount of air pressure (a generalized statement). Say for example using normal good ol fashion air, it would not be uncommon to see pressure increases of 2-4 pounds at the end of a race. This is caused by the heat build up in the tires. This increase in pressure would mean the car would handle considerably different during the end of the run as opposed to the beginning. We used Nitrogen because it would retain that same tire pressure throughout the end, giving more consistant handling characteristics.
I suppose the same could be true for the big cars, but I have no personal experience in that regard.
that costco is putting nitrogen into passenger cars is snake oil to some extent...most sunday drivers would never feel the difference in tire pressure and the handling of their cars.
I suppose the same could be true for the big cars, but I have no personal experience in that regard.
that costco is putting nitrogen into passenger cars is snake oil to some extent...most sunday drivers would never feel the difference in tire pressure and the handling of their cars.
06-23-2006, 05:09 PM
#36
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Originally Posted by slider
all I know is from my kid's quarter midget racing experience...we'd set tire pressures based upon track conditions and weather. you want better grip, reduce the amount of air pressure (a generalized statement). Say for example using normal good ol fashion air, it would not be uncommon to see pressure increases of 2-4 pounds at the end of a race. This is caused by the heat build up in the tires. This increase in pressure would mean the car would handle considerably different during the end of the run as opposed to the beginning. We used Nitrogen because it would retain that same tire pressure throughout the end, giving more consistant handling characteristics.
I suppose the same could be true for the big cars, but I have no personal experience in that regard.
.......................................
I suppose the same could be true for the big cars, but I have no personal experience in that regard.
.......................................
06-30-2006, 01:00 AM
#38
Ok I was so disgusted that I was "fooled" by Costco when I bought my Pilots Sports that I just went to the garage and purged all the Nitrogen from my new tires!!!!! Anyone have a compressor? Maybe a can of Fix-O-Flat??? 
Wonder how I'm gonna get to work tommorow??
Curse you COSTCO!!!
Wonder how I'm gonna get to work tommorow??
Curse you COSTCO!!!
