Aircraft recaps would be ok on my coach. (1) Airplane tires are rotational(one direction, birth to death. (2) FAA requires nitrogen only. No moisture to migrate to cords and present rust problems. (3) Sprial wrap, seperate textile cords are layered within the replacement tread rubber as it's applied to the tire casing. (4) Time release sidewall antioxidant to prevent cracking. (5) Heres the big one, Tires that have a puncture that has penetrated the innerliner are not repairable..........Thats a flat tire to us........ Guess if I was going to buy some recaps, I'd look inside the tire and see just what I'm getting. Think the last airplane tire I owned was 28 ply.
Nitrogen, that is very interesting. We use that on our hydraulic system accumulators. I would be interested to know the reasoning, is it just for reducing the moisture?
My Father-In-Law used propane to inflate a trailer tire the other day, I had not heard of doing that. He is a Rancher here in Texas, I thought of all kinds of reasons NOT TO. Maybe I am wrong.
Interesting thread NJT5573.
Happy Trails,
Paul
Dreamscape
Check out this info.
http://www.nitrogendirect.com/N2Info.htm
1. nitrogen molecules are larger...thus it doesn't seep through the rubber
2. Nitrogen does not expand as much in volume when heated compaired to air
3. Tires run cooler
Eliminating oxygen from inside the tire reduces tire aging too.
A flat on a plane is a very different issue than on a bus. Neither is good, & I agree that treating our bus tires better is a good idea. My issue with recaps is the unknown history of the casing.
"1. nitrogen molecules are larger...thus it doesn't seep through the rubber
2. Nitrogen does not expand as much in volume when heated compaired to air
3. Tires run cooler"
A rigorous scientific explanation to back these up (in a practical situation) would add some interest to the thread.
Tony
I know of some antique car collectors who maintain a nitrogen tank to keep their tires inflated. It is relatively inexpensive to buy a bottle and a regulator.
Richard
I've seen nitrogen generators advertised, expressly to inflate automotive (and truck) tires to the tune of over $1400.
I think I'll skip it.
ED
78% of the air we breath every day is nitrogen. This sounds like a scam to me.
NJT,
You must have had a heck of a big airplane to have 28 ply tires. My airplane has 4 ply and came originally with 2 ply!
Nitrogen may be required in transport class aicraft but not in light aircraft. 99% of lightplanes use just plain ole local air.
High flying airplanes use nitrogen so the tire won't expand so much at very high altitudes.
Also in light aircraft there is no requirement to replace a punctured tire, repair is up to the A&P doing the work. The only no-no I know of is tread worn down to cord, cuts to cord or deep cracks.
Lightplane tubes used to be made of natural rubber and so would lose air through the tube over time. Don't know if they still are but mine leak down so I guess they are.
teke,
1. Don't buy this one, air is mostly nitrogen anyway.
2. Agree with this one
3. They don't run any cooler they just don't expand as much.
Nitrogen is the latest scam, another way of milking vehicle owners of their dollars. It is obviously better than air but not necessary for normal use.
The biggest problem with nitrogen is that it comes in very high pressure cylinders. Those things can blow a tire to shreds and you too.
Indeed, 78% of regular air is Nitrogen, but it is the water vapor and that pesky little 21% Oxygen that make air less stable. As for how much real benefit there is in using Nitrogen for standard vehicle usage, I am doubtful. I've seen a lot of claims but I feel like it is just a vanity trend.
As I understand it, the reason commercial airlines, military aircraft and the space shuttle use Nitrogen in their tires is for the temperature stability and dryness. The tires can get extremely cold at high altitudes and then heat very rapidly on touchdown. Race cars also use it for temperature stability since their tires get extremely hot. In collectors cars I can imagine the anti-rust and antioxident qualities of Nitrogen (it is a primarily inert element) being mildly beneficial but still more vanity than functional.
I always thought that water vapour and all of the major constituents of air act essentially as ideal gases whose behavior as temperature changes all follow the Gas Law. This means that at practical temperatures found in tyres, the increase in pressure for a given increase in temperature will be the same for normal air as for say, nitrogen.
The only time this will vary a little - and will mean the air mixture giving a lower pressure than nitrogen - will be if the temperature inside the tyre falls below the dew-point causing some of the water vapour to condense out. This effect is small and would need some accurate instrumentation to pick it up.
The amount of water the air in a tyre holds is quite small -- a maximum of about 5 grams. Commercial aircraft fly at high altitudes where the temperature is way below zero and so the effects of ice causing out of balance during the great acceleration as they contact the ground could be significant
As for the oxygen inside the tyre. This is the same as the oxygen on the outside of the tyre and since the UV light and road contaminants are also on the outside of the tyre, it is not surprising that the outside of the tyre is the side to show aging well before the inside.
Tyres running cooler? Maybe the thermal conductivity of nitrogen is different to that of air, but it is hard to see how that would have any significant effect on the tyre temperature. It could be argued that if nitrogen was a better conductor then it would conduct more heat from brake drums and make the tyres hotter. Anyway, it would have to be a second or third-order effect and be far less significant than the much higher temperatures of those tyres on the sunny side of the vehicle.
As for using them on road vehicles -- aren't they all very rounded compared to road tyres, and designed to operate at significantly higher pressures in completely different operating conditions?
As for size of molecules -- oxygen atoms are heavier and so presumably bigger than nitrogen atoms so I guess the molecules might be bigger too -- and anyway, I doubt whether relative permeability of half an inch of tyre rubber would be of any significance at all compared to other types of leakage paths.
The last time I had my tires rotated at Costco, the tire stems had green plastic caps on them, which sort of pissed me off since I had chrome metal ones with O rings (I didn't notice till a few days later). The green caps means the tire has been filled with nitrogen. Costco does that for free, as a matter of policy (at least at the Costco I go to). Good Luck, TomC
Here is the story behind Costco's use of Nitrogen. (article on right side of page)
http://www.costcoconnection.com/connection/200410/?pg=17 (http://www.costcoconnection.com/connection/200410/?pg=17)
I think the benefits they cite are based on careless, or automotively clueless, drivers that don't monitor their tire pressure. A low tire will waste fuel and run hotter. But I don't see any way that a Nitrogen inflated tire will outperform a properly maintained tire inflated with standard air in standard road usage.
If the claim about seepage resistance "holds air" (pardon the pun) then I could see it as a fuel saving measure for drivers who don't routinely check their tires. Perhaps it would be a convenience for those of us who do monitor our tire pressure, fine if it is free but not worth added expense.
On the question of oxygen leaking through the rubber faster than nitrogen, then I agree with Hightechredneck. If you initially fill the tire with 78% nitrogen (ordinary air) and assume that you let all the oxygen escape before topping it up then the tire will be 96% nitrogen (20% of the 20% lost). Do that a second time and the tire will be over 99% nitrogen (the same as the expensive nitrogen generators produce).
Obviously, you don't wait for a 20% loss before you top up, but this just shows how quickly you can change the percentage of nitrogen in the tire by replacing the lost oxygen with ordinary air.
On the topic of leaking: Last summer I donated an old vehicle to a museum. It had new tires and tubes installed in 1964 and sat around outside until 1985 when I moved. I trailered it to my new place and parked it in the back of the shop. When I took it out last year, one tire was flat. The other three looked OK and I didn't have to add any air before loading it.
Here is some info I read while looking for tires on my BMW motorcycle, about nitrogen.
Nitrogen: There is a lot of misrepresentation, and just plain hype, on the use of nitrogen in any type of tire for road (and off-road) use. The facts are, that while there ARE benefits, use of nitrogen to fill tires is NOT practical, for anything but pure racing. On the plus side, molecules of nitrogen are larger than average air molecules. These larger molecules do NOT pass through the rubber used in tires and tubes, as easily as common air molecules. Thus, pressure loss over time is lower. Another plus, is that nitrogen is less prone to accumulate water vapor. Water vapor in common compressed air in tires can lead to rather wild fluctuations in pressure as the tire heats up, and cools down. Obviously, this is minimized by using clean, dry, air. Nitrogen is, due to its lack of extra affinity for water vapor, a safer, more stable, tire pressure, which can be somewhat important for very high speed driving (much more so at racing speeds). The final good point about nitrogen is that it does not contain oxygen, which tends to degrade rubber compounds over long periods of time.
The PROBLEM with nitrogen is cost, not easily available, and if you top off the tire with even a very slight amount of compressed air, the advantage of the nitrogen is LOST.
Aircraft tires!
Well for one thing if you were to put them on a coach you would have to locate split rims as I don't think you could mount these type many ply tires on a regular type Accuride type 22.5 rim.
Also I don't think that you could get very many miles out of a aircraft tire like you will get out of a 12R/22.5 tubeless tire.
The main cause of tread wear on a aircraft tire is not rolling down the runway but landing and braking the airplane to a slow taxi speed.
Airline industry counts landings not miles on the tries.
The major air carrier that I retired from used recap tires and also new tires on their airplanes the tires were re caped as long as the tire carcuss was still good. I have seen quite a few tires that were re-caped more than a dozen times.
Each tire had it's own tire gauge that was used by the flight crew on their walk around inspection to check for low pressure or flat tire ::)after the airplane was sitting over night.
On maintenance checks we would check the tire pressure with a known accurate tire gauge (dial) type to see if the tires were inflated to a proper pressure.
Yes we did use nitrogen to inflate our tires.
Our source was a high pressure nitrogen bottle service cart (3000 PSI) which was reduced down to a lower PSI with a known accurate pressure regulator for servicing the tires.
Nitrogen in the airline aviation industry is wonderful as it is handy and required.
I use compressed air in my tires on all of my cars and my GMC bus/conversion.
Not to say that I would not use nitrogen it if it were as handy as my air compressor.
Hope this helps.
jlv
In my mind, the biggest benefit of nitrogen is it is DRY. Plain ole shop air isn't. How many have air dryers on your shop air compressor? Water inside a tire will make a mess of any tire ballancing powders too.
It's your bus, do what you gotta do.
Stan,
I really like your system-now I know how to get all my tires inflated with free nitrogen!!
Quote from: tekebird on January 27, 2007, 03:47:05 PM
2. Nitrogen does not expand as much in volume when heated compaired to air
The reason for this is the moisture content of "air." Pure nitrogen doesn't have moisture in it, and thus expands at a nice constant known rate. Racers have been using nitrogen filled tires for a while. Me? Yep, I race, but I use plain old cheap/free air. I know that if I start my tires cold with 30psi, when they heat up (usually within 1-2 laps) they will have 40-42 psi, which is the manufacturers recommended pressure.
- John
Speaking of airplane tires, here's what can happen to them if a brake locks up. Bummer.....ghanson
Wow...quite a lil flat spot on that one!
Yes, the mother of all flat spots. Here's a closer in, although it's not got a lot to do with busing. Only thing to do with this one is make a flower pot of it....g