Nitrogen filled tyres

[vince n]

I had four new so2's fitted and the tyre place suggested I fill the tyres with Nitrogen instead of air. Does not seem to make any difference to the drive. Has anybody any thoughts on the matter.
Yellow Chim 98 450

[d_drinks]

quote:
How much did they charge for this? Race cars use Nitrogen so it must be O.K. What happens if you have to top up with air? does it just dilute the Nitrogen? or does it cause some sort of chemical imbalance?
Quinny

Nitrogen is used in F1 cars etc. as it does not expand as much as air when heated. US race cars e.g. NASCAR, IRL, CART etc. still use air and have to compensate for how much the air will increase in volume as the tyre heats up. They say a good (i.e. professional) driver can detect a difference of 0.05 of a bar in tyre pressure, and this affect laptimes - hence Nitrogen in F1.

Not sure if in day to day use having Nitrogen in your tyres will have much of affect - track days would be a different story though.

Are you planning on many track days???

>> Edited by d_drinks on Thursday 11th April 08:57

[bryanlister]

Air is 80% nitrogen, 19% oxygen and 1% noble gases. I think unless you are Shooey or Richard Noble - filling up with pure nitrogen is very OTT!

[ATG]

Air is 80% nitrogen anyway. Also the behaviour of most gases is well modelled by the "ideal gas equation" PV=nRT, i.e. thermal expansion/pressure increase is nearly identical for all gases unless at extreme pressures or temps. I'd be suprised if anyone could really tell the difference.

[mactom]

Hi,

Remember: "Standard Air" is roughly 78% Nitrogen, 21% Oxygen and 1% other gases. Plus a varying amount of watervapour. The diameter of the O2 molecule is not that much different than the N2 molecule. Therefore you will not get a measureable effect of less loss of tire pressure as it is always advertised.

The only sense of filling tires with N2 is to use dried N2. This will protect wheels made out of magnesium or other light metal alloys from corrosion as no oxygen is present in the tire and you will be able to save the protective coating (and a few gramms) on the inside wheel surface. But, considered the permeability of our tires, this effect won´t last long. It also requires a proper drying of the tire before putting it on, as you have moisture on the tire itself. Maybe this dried N2 will have a very slightly different temperature behaviour and maybe does not expand that much when heated (compared to "humid" air or N2) but I guess you will not be able to measure a difference in tire pressure.

I have never heard of any advantage for standard wheels(except of more money for the N2 supplier ... ) of filling tires with N2. A 200 bar 50 litres N2 bottle is about 25 to 50 Euros in Germany. This will give you a fill of at least 100-150 wheels ... What did you pay per wheel? I have seen advertising in Germany, asking for 10 to 20 Euro per wheel for a N2 fill. Crazy!

Best regards,

Thomas.

[richardwakelin]

Remembering a little school chemistry the larger part of the atmosphere is Nitrogen anyway. Just did a search to remind me and found the following. Typical composition of dry air at surface altitude % by weight:
Nitrogen 75.521%
Oxygen 23.139%
Argon 1.288%
Carbon Dioxide 0.05%
Rare gasses 0.002
(source www.c-f-c.com/specgas_products/air.htm)

So most of what goes into any tyre is nitrogen. Now why it would be benefical to go to any lengths to eliminate the 23% oxygen (which is the majority of the remaining gases) illudes me. Maybe oxygen has different expansion properties? Of course oxygen is reactive and not something you want around in the event of fire. Maybe the tyre temperatures are such that some chemistry can happen with the rubber, but I wouldn't have thought F1 tyres stay on the car long enough for it to matter.

Is there a chemist or race driver in the house?

[yum]

Many years ago there was an advertisement published in a newspaper, encouraging BMW drivers to call in at their local garage to have the air in their tyres changed. I can't remember the purported reason for this...

except for the date....

April 1st.

Methinks someone is taking the p1ss.

R

[PaulGray]

I heard that the luxery car manufacturers i.e. Mercedes, BMW sent their cars out if the factory with the tyres filled with a gas other than compressed air,supposedly to give a smoother ride.

[d_drinks]

Rich - see my comments earlier in the thread -

quote:
Nitrogen is used in F1 cars etc. as it does not expand as much as air when heated. US race cars e.g. NASCAR, IRL, CART etc. still use air and have to compensate for how much the air will increase in volume as the tyre heats up.

quote:

F1 mag and Autosport ran articales before the start of the F1 season comenting on the use of Nitrogen giving the above reasons for it's use.

None of us mere mortals could hope to get to this level of car feel. F1 tyres are around 80 deg C when they are put on and they only get hotter as the race goes on - think 33 laps of Brazil on one set of tyres !! I spent sometime in a Tuscan racer and the tyres weren't even warm even though the car was being hammered by a professional driver (Michael Caine, not me ) Nitorgen in road car tyres is likely to be a tad OTT IMHO

[shpub]

The real reason is actualy moisture. Using air, you get moisture in the tyre which when it heats up can distort the tyre pressures and cause problems. With N2, there is no moisture and the problem goes away and you get predictable pressures. As a TVR on road or track day never gets the tyres to these sort of temperatures and there are other factors involved that can effect the handling... it is a little OTT for lesser mortals.

Steve

[ATG]

mactom's point about N2 being dry is a very good one. Excluding water vapour from the gas in the tyre might make for measureable differences in the temp/pressure relationship. Water falls into the "weird shit" category as its highly polar molecules tend to "hydrogen bond" to each other. The result of this is that initially you have to pump more heat into them to get an equivalent increase in pressure than you would for an ideal gas, but at some point as you start to overcome the hydrogen bonding completely, you probably get an accelerated increase in pressure for an increase in temperature as you get more free water molecules moshing about.


ah hah ... I see Steve has made the point too the water is the critical bit...


>> Edited by ATG on Thursday 11th April 11:26

[sybaseian]

Nitrogen is also used in aircraft tyres.....