Air or Nitrogen

[terje]

Last season I used Nitrogen in my tyres although when I tried to evaluate Air against Nitro the results didn't seem to be very conclusive.
The car is a single seater (465Kgs) with 170bhp, and large Michelin slicks.

The idea was that with short races I can go into the first corner with the correct ride height etc. because the tyres would be set to near hot pressure. On test days though the pressure rise was not significantly different to that of air. I understand evacuating the air is important but it is very difficult to achieve.
I’ve been evacuating the tyres by:

1. Empty the tyre of air
2. Over fill the tyre with Nitro
3. Then with the valve at the bottom of the wheel bleed out the air (thought being the molecular weight of air is grater than air).

I think the problem is there is still moisture in the tyre, which defeats the use of the Nitro. Is there a more effective way of achieving this? or is it better to use an in-line air dryer from the compressor?

[imull]

Originally posted by terje


3. Then with the valve at the bottom of the wheel bleed out the air (thought being the molecular weight of air is grater than air).

i assume you than the molecular weight of nitrogen is heavier than that of air

Air, however, is not a molecule in its own. It is a mixture of several elements. Of which it is something like this:

Nitrogen (N2) 78%
Oxygen (O2) 21%
Others (eg Carbon) 1%

As you can see the majority is already nitrogen.

I have not looked into it enough to know wheather it is worth it or not but there does seem to be a lot of influential people talking about using Nitrogen...

Try phoning Michelin. I would be surprised if they dont try to help you.

[REALIST]

Where did you get the Nitrogen from? If you got it from one of the tyre dealers who offer the service it was unlikely to be dry. Their machnes are not that well maintained and the filters are often way past their sell by. Unless you know the generator is OK, best to get a guaranteed dry cylinder from BOC etc.
To purge the tyre you will need to fill/ deflate 3 or 4 times. first fill to 30psi will give you 92/3%. Next one 96/7% and 3rd one 98/99%, which is as good as you'll get, assuming the stuff you are putting in is pure. That's theory of course!

[terje]

Originally posted by imull
i assume you than the molecular weight of nitrogen is heavier than that of air

Oops yes that’s what I meant. Yes I understand that majority of air is made of Nitrogen, but 78% isn't 100%. It’s the moisture in the other constituents that cause the increase in tyre pressure.

[terje]

Originally posted by REALIST
Where did you get the Nitrogen from? If you got it from one of the tyre dealers who offer the service it was unlikely to be dry.

I'm registered to carry BOC, its only £17 per annum. I get the Nitrogen in bottles from a local dealer that supply WSR.

[terje]

Realist, I take it you've had some experience with running nitrogen..is there a real benifit?

[BugEyed]

Being a Physics Teacher I have a couple of comments:

• The theory is that water expands about 2000 times when converting to a gas (steam, not water vapour).
• How much water is there in your tyres? I guess not much, so this strikes me as "a good idea" in F1 where eliminating any error is worth the cost, but probably b0110cks in other environments.

Sorry to be sceptical, but it is my view.

Duncan

PS My local branch of a nationwide chain of tyre merchants recommend it, but cannot justify it, but charge more for it.

[terje]

Originally posted by imull
i assume you than the molecular weight of nitrogen is heavier than that of air

No, what i said was wrong- its air thats heavier than nitrogen.

[imull]

just spotted that i got it wrong too (you said air is heavier than air) lol oops

[thebear]

Another possible advantage to Nitrogen is a reduction in oxidation from heat buildup because the ~19% Oxygen in "air" has been excluded. Of course the F-1 teams are after stability in the rubber but it is only "in action" for a very short time.

[Aircon]

Realist is right, you have to fill and evacuate the tyre 3-4 times to get any benefit so you do start using a fair bit of nitrogen to achieve this.

When done properly, it should greatly reduce "cold tyre syndrome" and make the car much more consistent from the first lap onwards.

However, proper dry air (and BOC sell this as well in cylinders) will accomplish a similar result without the filling/refilling of the tyre. The main culprit is the moisture in the air and the way to properly do it is to mount the tyre with the dry air/nitrogen after wiping out the tyre and the rim.

[Revracing]

Yes the cullprit for tyre instability when hot is the moisture content, However, don't be mislead into thinking that your tyres when properly moisture free and pressurised with nitrogen will not increase in pressure when heated, this is not the case.

Nitrogen will expand in pressure to much the same extent as air, this will effect tyre performance, some on track testing and development will still need to be done before you can safely say that you have engineered out this problem

[REALIST]

I have some experience in the development and use of the 'tyre trade' nitrogen generators and have also used Nitrogen in karts and race cars. Personally, I don't think that one would see much advantage from dry Nitrogen and dry air, but I wouldn't agree that there is likely to be little moisture in a race car tyre. Non of the compressors I have seen in use at ciruits are dried and most run their receivers up to high (10Bar) pressures. They also stand around cooling and a lot of water builds up in the receivers. I would guess that the air from these is pretty wet.
My experience? Karts on non-dried air, 20psi cold up to 25psi hot. Nitrogen, a couple of psi less hot. No noticeable difference in car tyres, unsure why.
As far as the advantage for road cars? Supposedly the pressure loss from tubeless tyres is lower and pressures remain more stable. I have no proof or reasons for this but do know that Lexus, Land rover and other prestige car manufacturers specify Nitrogen at Manufacture. More significantly they don't make a marketing thing of it so I would assume they believe the technical benefits to be worthwhile.
I shall endeavour to find out!!

[Onlooker]

If you get a vacume pum,that runs off a little electric motor you can suck a tyre empty in no time.I think that they are old air conditioner compresssors???????????? Suck the tyre completely empty,it don't look pretty and has nil air/gas of anytype in it at all. Then fill with Nitrogen,now in Australia we use Medical grade Nitrogen and it works really well,yes it allows for higher start pressures and is therefore more consistant over the long run.Any race team worth it's salt uses Nitrogen and reap the benifits,equally if you start wheel spinning due to poor set up the increase in pressure will be less and thus the degradation of grip less.
If you are allowed why not use "Bleed off's" like speed way cars do.That is what most teams use that havent had them banned and my guess is that your rules are slack enough to allow it.

[terje]

Thanks everyone its been very interesting reading your thoughts.

Onlooker, any ideas who manufactures "bleed-off's"?

[Onlooker]

Sorry mate but check out a speedway site or maybe someone like "Demond Tweaks" They come in like a pack of 4 ,it could even be a company like Olins as they had a little thing to calibrate them that looked a bit like a shock gassing gauge.
You can adjust the pressure that they bleed off at and are pretty reliable if you keep them well maintained,the only down side is that once they let the air our,say lap 3 or so if you have a Safety Car etc you will have to wobble around on low pressures for a few more laps than the others.