I found this while lookimg into tyre life.
www.nitronics.com/research.htm
On my 1989 Range Rover Vogue (US Spec 3.6L with all options) They rot before they wear out at 5000 miles a year about 1/3 of that in low range in very soft sand on the beach)
I am constantly using dressing on the outside but this site seems to say thay rot from the inside out...
Any comments?
~R
|
Humm I guess no one else drives so little that their tyres rot before they wear out... sorry I thought this would be an on topic post... guess not
~R
|
Actually I was thinking about it....
I didn't really understand your first note, other than the subject, and I haven't looked up the link last night.
However, in the traffic jam last night I did notice that they have Nitrogen Pumps for tyres as well as the more normal Air ones.
What's supposed to be the advantage then ?
|
Randolph
I'm a bit lost on this one.
The key factor in external 'rot' is UV light (sunshine), or perhaps, as you've said, contact with salt water, but that's pretty rare for most people. I'm sure Mark can confirm if the sunshine is a big issue in tyre life in Brazil!
Never heard of a car tyre rotted internally though. May be a problem in climates different to UK, but I'm not sure it would happen in the normal lifetime.
May be different with aircraft where the tyres are subject to very low temperatures at 35000 feet, followed by rapid flexing and heating on landing.
Main benefit of nitrogen - large molecule size so reduced leakage rate. Can't think of any other significant benefit.
The shuttle? - Beats me how a helium filled tyre retains any pressure. Must be a pretty trick material.
Regards
John
|
|
|
|
Well For Aircraft Tire rot is a more common problem Esp for those that use grass fields or for other small private aircraft so it has been normal there for years O2 and O3 are the things that rot tyres the fastest
also Air can have a lot of water in it and if it freezes can cause out of balance problems in the winter until the tyre warms up and it melts (which also can cause special Aircraft problems when a chunk of ice breaks loose in a tyre at 160mph while landing it can tear up the inside of the tire...
in cars and trucks I would expect the main benifit to stop tyre rot from the inside out... not many will demout their tyres ever few months to put a dressing inside the thing... and most of the world will weare out tyres before they rot
~R
|
And, for the chemically ignoranbt such as myself, there's no fire risk with Nitrogen ?
And despite my lack of knowedge of things chemical, wouldn't there be some issue with the potential for permeation depending on the molecule/atom size ?
I'm sure I remember reading somewhere that different gases can need different seals/valves ? Or am I just totally confused ?
|
|
|
|
Air is 70% Nitrogen N2 which in the absence of things like electric sparks is inert there is on problem with leakage... some high tech applications (Space shuttle?) use He for the tyres I think don.t know why but it does leak through almost anything
I do not see a down side other than finding places that provide it
~R
|
Well, strangely, it seems pretty common here. I really don't know why that should be, unless its advantages are related to heat and expansion.
Its the end of winter here and the temperature today was 37 degrees. It will get a lot hotter and it plays hell with cars & fuel, and I guess, tyres.
But then, gas as engine fuel is also pretty common here, more common then diesel.
Which triggers another, mostly irrelevant, thought in my mind, with approximated conversion rates, then fuel cost here is as follows;
Gas - 25p per litre
Diesel - 34p per litre
Petrol - 50p per litre
|
|
|
|
I cant think of any related to heat and expansion... At the presures we are using here almost anything would obey the Ideal gas law...
Perhaps to help withthe rot problem in a hotter place?
|
|
|
Well the Paper on the site refernced in the first msg ends with this bit about leaks... I have seen Water being caried over in petrol station air pumps and seen rust inside of rims from it so it seems plausable But the paper is on a site pushing a product
*************
Today probably 99% of all tires are tubeless - truck, passenger, giant - and these tires are inflated with air, and all too frequently with wet air, i.e. air where the water has not been drained from the compressor tank as it should be. This moisture laden air (oxygen catalyzed by water) attacks the paint in the wheel well ultimately penetrating the paint and oxidizing the iron below it to form iron oxide or rust. Even aluminum is not immune from rusting, forming aluminum hydroxide, that gives an extremely fine dust that is difficult to even see inside the tire. The iron oxide rust is present within the tire in varying sizes ranging from coarse to extremely fine. Aluminum hydroxide dust is never coarse only extremely fine.
Whenever a tire is checked for its inflation pressure the pressure gauge requires a small gulp of air to activate the gauge. When the small gulp of air escapes from the tire the turbulence created picks up the finely divided rust and the dust enriched gulp of air passes around the open valve core which has been opened by the tire gauge. When the valve core drops backward into place after the gauge is removed some of the tiny rust particles get trapped between the rubber or plastic seal and the metal housing surrounding the seal.
This results in an extremely slow air leak that all too often escapes detection by the person gauging the tire and unless a metal valve cap which has another sealing surface in it is screwed onto the valve stem the tire will continue to lose air, albeit very slowly. When a larger rust particle is trapped between the core and housing, the escaping air is easily recognized so that proper action can then be taken immediately to correct the problem.
The perennial problem of low tire inflation can be effectively solved by the simple expedient of using nitrogen to inflate tires. Nitrogen is dry and contains no moisture. Nitrogen is inert so rust cannot form since there is neither oxygen nor moisture present to cause oxidation of the wheel
**********
|
|
|
Randolph
The nitrogen is not used as an anti-rot treatment in aircraft, most commercial airplanes have their tyres remoulded too regularly for the rubber to rot!
The reason in planes is that nitrogen is inert, cheap and helps reduce the risk of fire in an emergency stop as there is no oxygen to feed the fire from inside the tyre. Same at 35,000 feet, lack of oxygen in the air outside, so remove the oxygen from inside the tyres also.
I suppose you could use helium to reduce the unsprung weight on a car by a few grammes, but you'd be reduced to giggles if there was a leak.
Colin
|
|
|
With you On Jet Tyres as I am an ex ATP (though I think the dryness is a major factor as well) but on light aircraft esp ones that run from grass fields the do rot first And Even if coated on the outside with anti rot dressing compound they seem to rot from the inside when filled with air and I see the same thing on the tyres on my Range Rover
from the web page again As I have had Private email saying that it could not be reached...
*********************
THE ENEMY - OXIDATION
Causing the deterioration are oxygen molecules contained in the inflating air which is a mixture of gases - nitrogen 78%, oxygen 21%, argon 0.9%, and miscellaneous O.1%. Tires are designed to be protected from this deterioration by their liners which are supposed to keep air from percolating through them into the tire body, which they never do, and by chemicals called antioxidants or age resisters whose job is to intercept and neutralize any invading oxygen - which they do until they are themselves used up, which occurs too soon after a tire enters into service.
So the deterioration spreads. It starts within the tire interior and moves outward. it first invades and consumes the tire liner. It then ravages the insulation rubber adjacent the liner. It marches inexorably outward - because of the pressure differential of the tire inflation on the inside and the atmospheric pressure on the outside. As the decay moves ever outward - the oxygen molecules react chemically with the unsaturated double valence bonds present in all rubbers, causing the rubber molecules to lose their strength and their elasticity, so that they no longer act as rubbers, but instead take on the characteristics of a non rigid plastic. The decay is constantly being fueled by the fresh all too often moist air being injected into the air chamber to maintain the desired inflation pressure.
How do you get a truck tire to go a million miles? It's simple. TAKE THE OXYGEN OUT OF THE AIR!
TRUCK TIRE TESTS
A total of 175 truck tires were tested until they were worn down to the tread wear indicators (TWI). About 125 of these tires wore out without failing at mileages ranging from 125,000 to 225,000. About 50 of the tires failed physically at varying mileages generally on the low side. All the tires had been carefully monitored, measured for tread loss etc., and inspected at 10,000 mile intervals, a lot of them at 2000 to 3000 mile intervals. Tire sizes were mostly 11R24.5 & 11-24.5 with a very few 10R20 and 10-20's. About half of the tires had operated over the eastern part of the United States while the other half had run mostly in the southwestern part of the U.S.
When the tires were removed from service small samples of tread rubber were taken from the shoulders of the unfailed tires and from the actual failed areas of the destructed tires. These specimens were then subjected to the electron microprobe examination that has been described previously. The examination was specifically directed at determining oxygen and sulfur levels which was best accomplished by using IOKV (10000 electron volts) electron beam And an exposure of 30 seconds.
Both of the figures tell the same story. When a tire lives to wear out, the oxygen slowly migrates and permeates its way into and through the tire cord body and finally into the under tread and then into the tread itself. It takes a long time for an appreciable amount of oxygen to reach the tread since most of the oxygen gets waylaid along the way by the liner, and then the cord arid cord insulation compound.
One reason that truck tires can run 250,000 miles with the original tread while passenger tires can only go 50 to 60,000 miles lies in the relative bulk of the 2 different tire bodies. The bulkier the body the longer it takes for the oxygen to work its way into the tread. Unfortunately the bulkier the body the higher is the heat buildup and the faster is the rate of oxidation of the available double bonds. Once the tire body is all oxidized the tire is dead no matter how much tread remains on it. The thinner the tire body the lower the running temperature and the slower the rate of oxidation with a correspondingly longer life.
Practically all tire engineers throughout this century attribute the gradual loss in tire strength to be the result of "fatigue" when in reality this "fatigue" is nothing more than a slow inexorable oxidation taking place at the available double bonds of the rubber molecules.
**************
|
|
|
