Nitrogen in Tyres?

WellKnownSid

Keep_pedalling wrote: »

The hypothesis that nitrogen filled tyres will loose pressure slower than air filled ones is exactly that a hypothesis, I can't find any independent research to say this is true.

If you had a situation where all the pores in tyres that allow gasses to escape the tyre were slightly larger than oxygen molecules but smaller than nitrogen ones then this might hold up, but if some were large enough to let nitrogen molecules through then it will make no difference, and it is highly unlikely that the pores would be of a uniform and precise size.

There is a lot of research that clearly shows different gasses pass through simple rubber membranes at different rates. So when ATS / Kwik Fit / whoever tells us that Nitrogen is better because Oxygen escapes faster through rubber they are absolutely telling us the whole, undoctored, 100% justifiable indisputable truth.

But, as the brightest amongst us will have spotted, modern tyres aren't actually made of rubber any more...

In particular, tubeless tyres used in cars are constructed with an impervious layer designed to prevent whatever's inside from escaping, amongst all of the other complex materials they use in constructing a tyre.

These rogue air molecules, if they do escape, will be doing so between the bead and the wheel - or the valve if it's old. Getting the wheel and tyre properly cleaned / fitted / sealed will have the biggest impact on loss of pressure over time.

droopsnoot

stator wrote: »

I'm not sure how you are supposed to check if your tyres have nitrogen in them so you can get your refund

I wasn't paying a lot of attention, but I don't think there was any kind of requirement for you to prove they weren't filled. The gist of it was that if you've been charged for Nitrogen, you can take the tyre back and they'll fill it with Nitrogen. And I think you get the voucher as well.


Kwikfit page on their response is here: https://www.kwik-fit.com/watchdog

MoneyMate

Fill with :T Laughing Gas :T gives a more pleasant ride.

Alexd52

Nodding_Donkey wrote: »

Anyone who goes to Kwikfit deserves all they get.

One of the arguments for using nitrogen is that the larger molecules don't leach through the rubber and they maintain pressure better.

If that's true just keep topping up with air (80% nitrogen) and eventually all the other gas will leach out leaving just the nitrogen. Voila!

Just one flaw with this, oxygen molecules, making up 21% of air, are actually slightly larger than nitrogen molecules.

ceredigion

!!!!!! wrote: »

Fill with helium, you get a lighter ride

I have used helium in bicycle tyres before now. (tubs) for track racing at 220psi

agrinnall

Alexd52 wrote: »

Just one flaw with this, oxygen molecules, making up 21% of air, are actually slightly larger than nitrogen molecules.

Actually, that appears not to be the case. My CRC Handbook of Chemistry and Physics (5th Ed., 1977-78, p. F-210) lists molecular diameters measured in cm x10-8 (at least, I think it's -8, the print is very small and even in good light I can't be sure) as follows:

Nitrogen 3.15 (measure by velocity and from van der Waal's equation)
Oxygen 2.98 from velocity and 2.92 from v.d.W

It is a few years since my time studying chemistry so it could be that measurement techniques have changed since then and reversed the relative sizes.

Although I'd strongly suspect that the volume of gas lost through the tyre material is considerably less than that lost through poor seal with the rim and dubious valve seats.

oldhand

!!!!!! wrote: »

Fill with helium, you get a lighter ride

I just use propane,more bang for your buck as the yanks say....;)

BigBopper

silvercar wrote: »

Is that £5 voucher per tyre, per car or per customer?

They said per customer, on top of the refund.

dacouch

I think they were carrying out an experiment to look into the placebo effect on boy racers as to how much it improved performance.

Yolina

dacouch wrote: »

I think they were carrying out an experiment to look into the placebo effect on boy racers as to how much it improved performance.

So full of hot air then...