A friend tells me that Kwik Fit are apparently offering to fill your new car tyres with nitrogen for better performance. Only a matter of time before we're told it's better for bikes, surely? Anyone done a "Pepsi challenge" on this to see if it really is better?

What's the composition of air? How often do MTBs get punctures relative to a car? 😉

Air mostly…..

Nitrogen is used in motorsport etc so they don't get changes in tyre size as the air in the tyre heats up so closer control of ride heights.
I cannot really see the point on normal run if the mill road cars,
Also most MTB riders use there thumb to set tyre pressures
l.o.l

I agree. Just wonder how long it will take for somebody to turn up and try to convince us that it's another essential performance enhancing option for the bike.

surely helium would be better 🙂

I like to use an approximate ratio of 4 parts nitrogen to 1 part Oxygen in my mountain bike tyres.

Not tried many other ratios though as I was happy with that one and always have been.

I would like to try helium though as it could shave a few grams off the bike weight.

Nitrogen is used in motorsport etc so they don't get changes in tyre size as the air in the tyre heats up

all normal gasses have the same temperature expansion coefficient

I would like to try helium though as it could shave a few grams off the bike weight.

for a short while – helium atoms are small and leak fast 🙁

The benefits for car tyres are small unless your in to track days or speeds that are in excess of the limit in the uk.
Certain car's come with nitrogen filled tyres but this can be replaced with normal air as and when needed.
I deal with car tyres everyday on behalf of a major lease company and they have decided the cost out weighs the benefits, and it's only £1 a corner.
Most of the KF centres also arn't overly impressed with it.
If it was going to be that big a thing I'm sure the other major players would have taken it on board by now as well. I mean KF arn't exactly quick on the uptake with things, they still say it's not possiable to repair run flat tyres.

for a short while – helium atoms are small and leak fast

Bung some stans in there, that'll hold em in!

http://ahotcupofjoe.wordpress.com/2008/07/05/nitrogen-filled-tires-a-scam/

A quote from the Kwikfit web site
"Nitrogen
Filling your tyres with nitrogen may seem odd but that’s exactly what motor sport and aviation professionals have been doing for years. Nitrogen is completely safe. And by using it in a mixture with oxygen to inflate your tyres the theory is that it’s possible to negate the issue of slow deflation, which is caused by oxygen slowly infusing through the tyre wall from the atmosphere.

Having a tyre that does not deflate means you will improve fuel consumption and will probably improve safety standards too. It’s not yet standard practice but Nitrogen could well be here to stay as a result."
http://www.kwik-fit.com/tyre-technology.asp

"….slowly infusing through the tyre wall from the atmosphere"

Sort of destroys any cache value of being able to say that you have 2% more nitrogen in your tyres than the next guy when it is Kwikfit nitrogen.

The filling your tyres with nitrogen idea is just so in motor sport at least you have cylinders of nitrogen ready to use instead of a noisy compressor waiting to break down when you most need it.

Plus the process of purging the air from car tyres several times to try to get a higher concentration of Nitrogen in the tyre is only going to gain 3 or 4 % nitrogen.
http://www.carbibles.com/tyre_bible_pg3.html

aircraft use nitrogen mostly in order to ensure the gas is dry more than anything else

btw, it's cachet 😉

Nitrogen is completely safe

Try telling that to anyone who's tried breathing 100% nitrogen. I doubt they'll agree!

This trend comes from Nissan. They inflate GTR tryes with nitrogen as they claim oxygen is not stable enough. The idea being that the tyre doesn't expand as much when it heats up so tyre pressures are more predictable.
In teh aerospace industry thats understandable given that the tyres get heated up very very quickly on landing and blowing a tyre up due air expansion would not be good. In motorsport F1 in particular they use tyre pressures to control ride height and to control small bump absorbsion becuase the suspension is so stiff must of the work is done by the tyre and a few psi here and there makes alot of difference when laps times are measure in 100th's of a second.

Every for track day's nitrogen filling is pointless for the standard motorist. On a MTB it makes very light sense at all, you just don't get much heat into the tyre unless your somewhere that is already hot and in that case you will have pumnped the tyre up when it was hot. Its a waste of money, time and effort.

Not just cachet (looks too much like crochet, sorry) but improves road holding.
http://www.uniflate.com/
Do your hands not get dirty if you hold the road?

In the 1930's Mercedes were concerned about tyres reacting with the oxygen in the tyre but realised that it was not worth worrying about.

Nitrogen does obey Boyle's Law
http://www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html
and Dalton's Law of partial pressures.

The aerospace requirement for dry air is because any moisture (however small) could freeze in the tyre with possible wheel balance problems.

This stuff about nitrogen and pressure…….. how do the nitrogen suspension systems of Citreon cars work? how do air compressors work if air is 78% nitrogen? how does the internal combustion engine work? why do modern engines have EGR valves?

In the owners manuel for the GTR is says something along the lines of the nitrogen is less prone to pressure changes when it heats up, but if no nitrogen is avaliable just fill with normal air.
I've got the full wording somewhere on my desk at work, but alas i'm not at work now.

Try telling that to anyone who's tried breathing 100% nitrogen. I doubt they'll agree!

If I put you in a sealed air tight room filled with 100% O2 how long do you'll think you'll last?

Costco put nirogen in your tyres for free when you put new ones on.

Costco put nirogen in your tyres for free when you put new ones on.

somewhere within the price of the tyre you will be paying for it.

somewhere within the price of the tyre you will be paying for it.

Well of course but it'll cost you the same for the tyres to have air in, so you can have with nitrogen in with no extra charge.

if it was going out of tyres into the atmosphere, wouldn't it be exfusing?

This stuff about nitrogen and pressure…….. how do the nitrogen suspension systems of Citreon cars work? how do air compressors work if air is 78% nitrogen? how does the internal combustion engine work? why do modern engines have EGR valves?

Do you want those questions answering?

Yeah I was waiting for someone to ask that dirtynap do you want to do it or shall I?

Nitrogen is completely safe

Try telling that to anyone who's tried breathing 100% nitrogen. I doubt they'll agree!

If I put you in a sealed air tight room filled with 100% O2 how long do you'll think you'll last?

OK, let me rephrase that. Using Nitrogen in an industrial setting, the risks associated with breathing it are well understood and steps are taken to make sure you don't end up trying to breathe it.
"You can't see it, You can't smell it, You can't breathe it"…etc.

No such safety concerns when using oxygen. Fair enough, you don't want to be putting O2 in places designed for N2, but that's a different discussion. Certainly wouldn't be inflating my tyres with O2 either.

But the point I was making is that "Nitrogen is completely safe" as attributed to the Kwik Fit (sic) website is completely wrong.

Yeah but it sitting in your tyres isn't putting you at any more risk than air filled tyres, that's their point. No that you can put your nostril over the valve and sniff it up your nose and be ok.

No such safety concerns when using oxygen

There are serious safety concerns with oxygen. Ever heard of oxygen toxicity?

If I put you in a sealed air tight room filled with 100% O2 how long do you'll think you'll last?

given normal pressure and functioning lungs quite a while actually. certainly longer than a person would in a 100% nitrogen environment.

I didn't say it was more dangerous, he said there were no such safety concerns.

such safety concerns when using oxygen

There are serious safety concerns with oxygen. Ever heard of oxygen toxicity?

or explosion risks

given normal pressure and functioning lungs quite a while actually. certainly longer than a person would in a 100% nitrogen environment.

Not that well it's harmful and will kill you, yes not as fast nitrogen but don't think 100% is harmless.

Anyway I think the point is don't put nitrogen in your mountain bike tyres they may kill you as nitrogen is more dangerous than 100% O2 but not as dangerous as air.

OK, oxygen toxicity is a similar concern.

Sockpuppet – I said no such safety concerns, I didn't say there were no safety concerns. Friend of mine blew himself and a hydraulic accumulator up a few weeks ago using O2 on place of N2. A mistake he won't repeat in a hurry.

Mess around with an oxy bottle, and catch a good sniff of it and you won't die. Your hangover will go away (and come back with it's nasty brother a few hours later!). Catch a decent whiff of N2, which has no O2 in it, and it could well be your last. It is a gas which really needs to be treated with respect, and to say "Nitrogen is completely safe" (as Kwik fit claim) is misleading and dangerous.

As for sticking it in yer tyres, as a common-or-garden road user? No point. Marketing bullshit really. Certainly no benefit in a bike tyre.

"….slowly infusing through the tyre wall from the atmosphere"

So the oxygen atoms 'infuse' through dense rubber against a pressure gradient of 2.2-2.5 times atmospheric pressure. ERM NO.
If the Nitrogen in the tyre being a smaller atom at double the pressure doesnlt escape the tyre how in hell can the oxygen enter the tyre?

Total waste of time. To gain any sort of gain, you need to purge the fitted tyre first before you fill it with nitrogen. Did a few years in the BTCC and FIA GT's and worked closely with Dunlop. Their tests proved very little difference between nitrogen and air from a compressor with a very good dry filter. You will find most teams, as we did, bought diving compressors to inflate diving bottles to use as inflation for tyres and to power the air guns

Catch a decent whiff of N2, which has no O2 in it

wrong, you'd have to have it exclusively available for breathing for at least 4 minutes to ensure brain death, though you would pass out sooner – it's only harmful by excluding oxygen, which you need.

If the Nitrogen in the tyre being a smaller atom

according to Wiki the nitrogen molecule is slightly bigger (despite the smaller atoms) than the oxygen molecule 300/290A, presumably due to tighter bonding with oxygen, but that's only a 3% difference

Lexus was one of the first car manufacturers to fill new car tyres with nitrogen because it resulted in a marginal decrease in road noise.

So if air is near enough 80% nitrogen and the oxygen gradually escapes through the tyre, by the time that 20% oxygen has escaped and the tyre has been reinflated with air, it will be 96% nitrogen.
Another deflation/inflation cycle and it's up to 99.2%.
Surely a tyre that's been on a few years will be close to 100% nitrogen anyway.

So if air is near enough 80% nitrogen and the oxygen gradually escapes through the tyre, by the time that 20% oxygen has escaped and the tyre has been reinflated with air, it will be 96% nitrogen.

no, because the nitrogen diffuses too, though possibly marginally more slowly

Oh, OK. So if the nitrogen escapes as well, albeit at a slower rate, it would take more cycles to approach 100% and it reduces one of the supposed benefits of using nitrogen.

This siteis a good write up of nitrogen in car tires – loads of detail. Conclusion is that it's a waste of time unless you're running a haulage company, and even then it's marginal.

Oxygen atoms are smaller than nitrogen atoms btw – size decreases across rows of the periodic table, despite the increase in mass. Hence O2 being smaller than N2.