Nitrogen Filled Tyres - Do I Need to Top them Up?

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alasta

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#233440 16-Apr-2018 14:21

A while ago there was a thread about the benefits, or lack of, relating to inflating tyres with nitrogen but I don't recall seeing an answer to this question.

When my car was last serviced the dealer filled the tyres with nitrogen, which was unnoticed by me at the time. I am now wondering if I need to monitor the pressure and top them up at the service station as I would normally do. If I top them up with plain air are there any potential problems with having a combination of both air and nitrogen in the tyres?

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#1997091 16-Apr-2018 14:24

Yes you need to monitor the pressure and nitrogen filled tyres are a SCAM and topping up with air from petrol station is fine

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cisconz

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#1997093 16-Apr-2018 14:26

Would they not then have Nitrous Oxide in them?

Hmmmm

alasta

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#1997094 16-Apr-2018 14:27

Brilliant, thanks. If they'd asked me if I wanted a nitrogen fill then I would have told them not to bother, but I only just noticed today that they have replaced the valve caps with new ones that have 'Nitrofill' or something like that so I'm assuming a nitrogen fill is what they've done.

gregmcc

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#1997117 16-Apr-2018 14:39

keep in mind the air we breath is 78% nitrogen already, did they evacuate all the air out of the tyre before filling with nitrogen? I doubt it. it is all a money making scan, I doubt there would be any noticeable change in performance if the tyres were filled with nitrogen

FireEngine

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#1997120 16-Apr-2018 14:42

cisconz:

Would they not then have Nitrous Oxide in them?

No, a mixture (N and Air), does not suddenly become a compound (N2O) ;-)

Regards FireEngine

Oblivian

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#1997125 16-Apr-2018 14:47

alasta:

Brilliant, thanks. If they'd asked me if I wanted a nitrogen fill then I would have told them not to bother, but I only just noticed today that they have replaced the valve caps with new ones that have 'Nitrofill' or something like that so I'm assuming a nitrogen fill is what they've done.

Or done the green cap trick and charged you $10/tyre for the air experience :)

SepticSceptic

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#1997128 16-Apr-2018 14:49

FireEngine:

cisconz:

Would they not then have Nitrous Oxide in them?

No, a mixture (N and Air), does not suddenly become a compound (N2O) ;-)

Someones laughing all the way to the bank :-)

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Bung

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#1997143 16-Apr-2018 14:59

I'd change the caps to ordinary black as the green might be like the old gypsy mark that labelled you as a soft touch. You might get less upselling 😉

MikeAqua

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#1997144 16-Apr-2018 15:01

gregmcc:

keep in mind the air we breath is 78% nitrogen already, did they evacuate all the air out of the tyre before filling with nitrogen? I doubt it. it is all a money making scan, I doubt there would be any noticeable change in performance if the tyres were filled with nitrogen

Every time I buy new tyres I get the choice of air or nitrogen for no extra cost. Free top ups too. Not much of a money making scam ...

If you fit new tyres they contain air at 15psi. If you pump then up to 30 PSI with N, half the new gas is N. So the resulting gas mix is ~90% N.

I did an limited experiment where I filled one side of my boat trailer (tandem) with nitrogen. So that's one tyre on each axl with nitrogen and one with air. Identical tyres. Identical age. All tyres to inflated to 43psi.

After six months there was a couple of psi difference.

That's a high load, with reasonably high pressure (over 45psi at highway temp) so maybe not applicable in all situations. But enough for me to get the air side replaced with nitrogen.

Mike

MikeAqua

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#1997155 16-Apr-2018 15:16

To answer the OP's question - yes you still need to check you tyre pressure. You can get a little handheld tyre meter for very little cost.

Usually whoever sold you the tyres will top up the nitrogen for you for free.

Mike

Bung

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#1997177 16-Apr-2018 16:00

MikeAqua:
I did an limited experiment where I filled one side of my boat trailer (tandem) with nitrogen. So that's one tyre on each axl with nitrogen and one with air. Identical tyres. Identical age. All tyres to inflated to 43psi.

After six months there was a couple of psi difference.

That's a high load, with reasonably high pressure (over 45psi at highway temp) so maybe not applicable in all situations. But enough for me to get the air side replaced with nitrogen.

Just to clarify, did you fill one side with nitrogen or 1 tyre on each side? Usually the tyres on the left get a harder time with more potholes and road debris. If you'd left that side filled with air the experiment might be biased.

In any case even though I haven't had a puncture in over 10 years I still regard nails and screws as more of a problem than slow leaks. Having nitrogen wouldn't reduce the amount of checking.

frankv

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#1997187 16-Apr-2018 16:41

I did the arithmetic on the gases (from memory of 1977 58.201 Inorganic Chemistry IIRC) and there's not much difference in leakage rate between air and nitrogen. The most important thing about nitrogen is that it is dry; in air-filled tyres water will condense and evaporate depending on temperature, and therefore the pressure may vary. A little.

alasta

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#1997208 16-Apr-2018 17:39

Thanks everyone. Based on the previous thread on this topic I wasn't hoping for or expecting any benefits from the nitrogen fill - I just wanted to clarify the maintenance side of things. It sounds like I'm fine to do what I've always done in terms of monitoring pressure and topping up with air as necessary.

ech3lon

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#1997255 16-Apr-2018 19:44

For what it's worth, I'd never pay for nitrogen fill, having said that, one of our car got free nitro fill with the new tires purchase and found them to require less top up (with regular air) than the other car with similar pressure and weight.

A quote from an article:
A 2007 Consumer Reports study compared air-inflated tires and nitrogen-inflated tires to see which lost pressure more quickly and whether the difference was significant.

The study compared 31 different automobile models with tires inflated to 30 psi. They followed the tire pressure for a year and found air-filled tires lost an average of 3.5 psi, while nitrogen-filled tires lost an average of 2.2 psi. In other words, air-filled tires leak 1.59 times more quickly than nitrogen-filled tires.

https://sciencenotes.org/nitrogen-versus-air-better-tires/

They'll still need top up eventually, just maybe a bit less often?

Aredwood

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#1997259 16-Apr-2018 19:53

frankv:
I did the arithmetic on the gases (from memory of 1977 58.201 Inorganic Chemistry IIRC) and there's not much difference in leakage rate between air and nitrogen. The most important thing about nitrogen is that it is dry; in air-filled tyres water will condense and evaporate depending on temperature, and therefore the pressure may vary. A little.

The air compressor at the tyre workshop is almost certain to run at a much higher pressure than what car tyres are normally pumped up to. Most of the moisture would condense into the bottom of the air storage tank on the compressor. As increasing the air pressure causes the moisture to condense out.

So although workshop compressed air won't be 100% dry. It would still be dryer than ambient air.

And the outside of the tyres would always get exposed to far more moisture anyway.

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