Lotus Elan

Tyre aging and the use of Nitrogen in tyres.

PostPost by: billwill » Thu Apr 12, 2018 3:19 pm

Here are some interesting articles on tyres relating to the rubber aging etc
and another on the use of nitrogen in tyres (something I had never heard of).

https://www.thoughtco.com/the-science-o ... ng-3234377

https://www.thoughtco.com/nitrogen-in-tires-607539
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PostPost by: 69S4 » Thu Apr 12, 2018 4:21 pm

billwill wrote:r on the use of nitrogen in tyres (something I had never heard of).
https://www.thoughtco.com/nitrogen-in-tires-607539


I noticed a few years ago my local tyre depot was plastered in posters about the wonders of nitrogen and the staff were advocating its use with the zeal of the born again. We even had a few of our wheels done when new tyres were being fitted as paying the extra was cheaper than arguing with them. I can't say I ever noticed any difference.

When we were having a couple of tyres fitted there a few weeks ago there was no mention of it, no posters, nothing. I wonder why. :roll:
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PostPost by: alan.barker » Thu Apr 12, 2018 4:41 pm

Are you sure they fill the Tyres with nitrogen or is it a way to charge you more :roll:
Do they have an Air Line + a Nitrogen Line :wink:
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PostPost by: 69S4 » Thu Apr 12, 2018 5:00 pm

alan.barker wrote:Are you sure they fill the Tyres with nitrogen or is it a way to charge you more :roll:
Do they have an Air Line + a Nitrogen Line :wink:
Alan


Wasn't there some shock horror tv expos?s - BBC Watchdog or similar - where they secretly filmed tyres being pumped up with compressed air round the back while the customers were being charged for nitrogen.
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PostPost by: Bud English » Thu Apr 12, 2018 5:06 pm

My last set of tires for the truck and the tires on my subcompact, when new, both came filled with nitrogen (green valve stem caps and all). That's a great beginning and all good in theory. The rub comes when you start to lose pressure even if it is at a somewhat slower rate than with air (78% nitrogen anyway). Finding pure nitrogen to top them up can be hard depending where you live. Setting yourself up with a pressure bottle and regulator will set you back several hundred bucks. Unless you are close to a tire shop set up with nitrogen, and most aren't, you end up topping up with good old air. Luckily I live where the air coming from my compressor is relatively dry.

I like Tire Rack's take on the subject. "Rather than pay extra for nitrogen, most drivers would be better off buying an accurate tire pressure gauge and checking and adjusting their tire pressures regularly". https://www.tirerack.com/tires/tiretech ... techid=191

...or better yet, get the accurate pressure gauge, air them up, and wear them out before they are old enough to deteriorate. :wink:
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PostPost by: Spyder fan » Thu Apr 12, 2018 6:18 pm

I remember my parents buying me a foot pump as a present along with a generic car maintenance manual upon the purchase of my first everyday car in 1977 ( a 1968 Mini 1000 mk2) the maintenance manual gave precise instructions regarding regular checks, the most important were, oil levels, water levels and tyre pressures on a weekly basis.
I studiously used the foot pump and tyre pressure gauge ( my Uncle gave me that) every Saturday and checked the tyres for flat spots, wear and other damage religiously, oil and water was checked and topped up as required at the same time, it was probably the most well maintained Mini in South London especially one of such an advanced age..... remember that any car older than 5 years back then was considered to be a banger.

You can buy a car these days that has 7 year unlimited mileage manufacturers warranty (Kia), my daily driver was only warranted for 3 years, but it?s a VW Golf, they really don?t go wrong and the computer tells me when the tyres need a pressure top up.... no nitrogen needed, just a bit of common sense to do a few visual checks on the tyres and check the oil and water at least once a month ( I still do it weekly).
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PostPost by: billwill » Fri Apr 13, 2018 10:58 am

Reading the two articles together the main benefit of using nitrogen as filler gas would not be the slower leakage, but the oxygen avoidance should let the rubber last longer before oxidising -> hardening -> cracking.

The earlier article seems to find that the tyre aging problem is mostly caused by the high pressure oxygen part of the air in the tyre.
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PostPost by: rgh0 » Fri Apr 13, 2018 11:42 am

I am no tyre expert but I also do not have any agenda. I also worked in the industry manufacturing rubber for major tyres manufacturers and understand the engineering principles around the design and construction of tyres and the rubbers that go into it and their operation.

A few comments

1. Nitrogen filling is a load of marketing hype. The leakage is no slower, the heat build up is no lower, the oxidation is no slower, in a road tyre the pressure stability not significantly better. The only potential benefit is that it is moisture free due to its cryogenic manufacturing process so the effect in race tyres that get very hot may be to improve their temperature related pressure stability a little.

2. Tyre aging is a very complex process and the tyre companies in response to potential lawsuits that would be hard to defend in this age of class action choose to go down an easily defend-able route of telling you to replace them as early as they think they can get away with... it does not hurt profits when it helps sell more tyres before they wear out also. Tyre companies make almost no money from OE fitted tyres, they make their money from replacements as the consumer tends to replace their tyres with the same brand so fitting tyres to new cars is really a marketing exercise. Rubber deterioration is principally driven by UV initiated free radicals and and sun exposure temperatures and cracking due to fatigue flexing.

3. The inner butyl rubber layer ( or before that the inner tube) is what seals the air in the tyre. The rest of the tyre is relatively porous and air (and oxygen and water) gets in and any leakage past the inner liner gets out so nitrogen on the inside makes no real difference to whats present in the tyre rubber itself.

4. Tyres these days last 10 time longer than they did 50 or 60 years ago from a wear perspective due to far superior rubbers and construction so aging is a potential problem more so now than maybe 60 years ago but in the real world nitrogen makes no difference and the failure of a tyre due to age in a car that is routinely used as an everyday driver extremely rare and driven by unusual environment factors before the tyre itself wears out. That does not say its not sensible to replace the tyres on your 30 year barn find before driving it :lol:

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Last edited by rgh0 on Fri Apr 13, 2018 12:24 pm, edited 1 time in total.
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PostPost by: Spyder fan » Fri Apr 13, 2018 11:55 am

Rohan,
That?s a very impressive summary of your thoughts on the matter based on experience and also expertise in the industry.

Do you have any thoughts on the other products that have done the rounds of being ?must have upgrades?, such as ?waterless coolant?, ?silicone brake fluid? and ?fuel catalyst pellets?? I have my own thoughts on all of those products, but I can?t claim to speak with any authority.


( Bill, sorry for the hijack, I can move this onto another topic if you want?)
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PostPost by: 69S4 » Fri Apr 13, 2018 12:15 pm

billwill wrote:Reading the two articles together the main benefit of using nitrogen as filler gas would not be the slower leakage, but the oxygen avoidance should let the rubber last longer before oxidising -> hardening -> cracking.

The earlier article seems to find that the tyre aging problem is mostly caused by the high pressure oxygen part of the air in the tyre.



Can't say I've ever taken a used tyre off of any vehicle and seen any interior degradation that's given me cause for concern. I replaced a tyre on a motorcycle a few months ago because of external cracks but the interior looked fine. That tyre dated from 1976.

I would have thought that it was the exterior that had most oxygen exposure. The interior gets pumped up but the oxygen concentration isn't "orders of magnitude higher", it's maybe two or three times higher and, apart from diffusion, not replaced (unless you get a flat). The outside gets constantly bombarded with not only oxygen but also ultra violet light (ok, not so much in the UK :lol: ) particularly in the sunshine states mentioned.

I wonder how much of the difference between the car companies stance on tyre life ("older than six years should only be used in an emergency") and the Rubber Association ("all tyres should be replaced 10 years from manufacturing date") is down to performance rather than safety.

The tyres on my Elan are coming up to 10yrs old and will get replaced before it does any serious miles this year but I've inspected all of them recently and there's no cracking or visible degradation anywhere on them that I can see - probably because they've spent a good part of that time in the dark in my garage. I'll be replacing them for "performance" reasons but if I was only puttering down to the supermarket (like my next door neighbour does in his 10yr old car) I don't think I'd give them a second thought.
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PostPost by: rgh0 » Fri Apr 13, 2018 12:21 pm

waterless coolant - again a waste of money and marketing hype. if you do the heat transfer analysis it is bad for your alloy headed twink and can lead to premature softening

silcone brake fluid - a valid synthetic fluid as a replacement. The issues with it are that it is more compressible and results in a soft feeling pedal. It does not absorb water like most glycol based fluids so its boiling point does not in itself drop overtime. However most water in brake systems gets into the wheel calipers past the seals as they move. In a synthetic system this water sits as water in the calipers and boils in the same way as the water cause normal fluid to boil thus you loose the pedal in the same way. The free water also causes as much or more corrosion than than the water absorbed into the glycol fluids

fuel pellets - There are many ways to add many things to fuel. Petrol companies spend millions of dollars formulating there fuels. Catalyst pellets are pure marketing hype. They cannot alter the basic thermodynamics of how an engine and its fuel operates. Some extra additives may have some benefits in some circumstances but most also have some downsides so i would use with caution and not expect miracles.


These are just my opinion based on being a mechanical and chemical engineer with 40+ years of interest in automobile engineering technologies, many years of work in petrochemicals, fuels, oils and rubber manufacture and a bit of experience playing with twinks and Elans. In general these opinions I can back up with sound engineering and science and analysis and they will be backed up by other expert analysis in these areas.

cheers
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PostPost by: alan.barker » Fri Apr 13, 2018 1:59 pm

+1 Rohan and 100% with you on these ideas.
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PostPost by: The Veg » Sat Apr 14, 2018 4:22 pm

rgh0 wrote:Tyre companies make almost no money from OE fitted tyres, they make their money from replacements as the consumer tends to replace their tyres with the same brand


Not always. My Mazda came with some really crap Bridgestones: noisy, only merely adequate in the wet, and short-lived. I did NOT want more Bridgestones after that (especially as they get consistent crap ratings in every user-review I've read) , and got some much more satisfactory Contis instead. I think Mazda just went with the cheepest USA-market tyre they could get when deciding what to put on at the factory.
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PostPost by: Elanconvert » Sat Apr 14, 2018 6:16 pm

rohan
just a small point regarding brake fluid......I used silicone dot 5 in he G4 and must say i did not notice any 'soft' feel to the pedal.....replaced the fluid in the elan last year with ordinary dot 4 and can't say there is any difference in the 'feel' of the elan brakes
I suppose it could be that all seals in the G4 were new, but only some of the elan's were....
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PostPost by: baileyman » Sat Apr 14, 2018 10:25 pm

I think I recall a story that with nitrogen you have no moisture in the tire. Moisture can result in pressure changes in hot tires at the limit making for curiously hard behavior to diagnose.

I haven't tested the idea myself. Could also be a load of bunkum.

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