Tyre Pressures

[OldBoyScout]

4 hours ago, gregoir said:

1 atmosphere of air pressure will be in the tyre before the nitrogen is inserted. The tyre will thus be inflated with a mixture of pure dry nitrogen and air. Unless there is a clever method of air removal?

Given that the air is 78% nitrogen there is probably not going to be enough moisture and other gases to make much of a difference. Moisture can probably be eliminated or reduced by fitting the tyre somewhere indoors with a dry atmosphere.

 

Alternatively pumping air out ought not to be much more difficult than pumping air in.

Edited 18 August, 2019 by OldBoyScout
Added a bit.

[Ootohere]

There are compressors for tyre inflation without good water traps or them drained and if you ever used one of those to spray with a spray gun and regulator you know to use a good water trap.

You get to know just how much H20 can be in tyres by corroded rims.  Location location location can mater when it comes to condensation in tyres, 

and ice inside tyres in winter is not unusual in older wheels / tyres when you remove them, or some H20 if not frozen.  (Tom Jones song.)

[OldBoyScout]

26 minutes ago, OldBoyScout said:

Alternatively pumping air out ought not to be much more difficult than pumping air in.

I'm probably wrong about this, as the tyre would collapse. Could cause damage and air would get in again.

[Alex-W]

11 hours ago, KenONeill said:

OK, I'll bite. How does filling a tyre with 100% Nitrogen rather than the more usual 80% exempt it from Gay-Lussac's law (also sometimes known as the pressure-temperature law).

 

Every day is a school day...  I just knew the Ideal Gas Law, which obviously includes this.   I guess they generally just teach that as it covers all bases.

 

I don't buy that n2 will make any difference on a road car personality.

As said, it's mainly about moisture as OFN has almost zero. 

And no grease easier, which is present in much compressed air.

But on a road car?   Really?  

 

As for corrosion and moisture, I've got a spare pair of wheels for my accord in my loft with no tyres on.  They were on the car for 19 years...  There's corrosion on them, it's all on the bloody spokes though, lol.

 

I agree about foot pumps...  They can be pretty terrible and the hoses perish after a while, however they do the job and are compact.  I just keep a double one in the garage and use that and a separate gauge to check all the tyres on all the cars every few months.  Don't trust the gauges on the pumps, you'd be more accurate kicking the tyre and guessing the pressure.

Edited 18 August, 2019 by Alex-W

[shyVRS245]

4 minutes ago, Alex-W said:

 

Every day is a school day...  I just knew the Ideal Gas Law, which obviously includes this.   I guess they generally just teach that add it covers all bases.

 

I don't buy try n2 will make any difference on a road car personality.

As said, it's mainly about moisture as ofn has almost zero. 

And no grease easier, which is present in much compressed air.

But on a road car?   Really?  

 

I agree about foot pumps...  They can be pretty terrible and the hoses perish after a while, however they do the job and are compact.  I just keep a double one in the garage and use that and a separate gauge to check all the tyres on all the cars every few months.  Don't trust the gauges on the pumps, you'd be more accurate kicking the tyre and guessing the pressure.

When I got home from the garage today checked the pressure the expert tyre fitter put in the repaired tyre and surprise surprise the tyre gauge I used read 2.9bar when the other 3 good tyres read 2.6bar. When I drove the very short distance to the garage with the slow puncture the pressure was 2.3bar. Draw your own conclusions as to why we should not rely on professional tyre fitters for accurate tyre pressures when leaving a garage.

[Ootohere]

You should not, you ask them what the tyre pressure was they set then check yourself. That is why a tyre pressure gauge should be in the car, 

or in your pocket when collecting hire cars, loan cars, fleet cars, cars after a service or new cars from a PDI.   People in the motor trade can kill you.

 

Reset your own TPMS. 'They can not know how different ones work, or want to interfere.

Edited 18 August, 2019 by Roottootemoot

[shyVRS245]

4 minutes ago, Roottootemoot said:

You should not, you ask them what the tyre pressure was they set then check yourself. That is why a tyre pressure gauge should be in the car, 

or in your pocket when collecting hire cars, loan cars, fleet cars, cars after a service or new cars from a PDI.   People in the motor trade can kill you.

 

Reset your own TPMS. 'They can not know how different ones work, or want to interfere.

I did reset the TPMS after ensuring all 4 tyres were the correct pressure. Just a cautionary tale to users of garages to beware.

[gregoir]

13 hours ago, OldBoyScout said:

I'm probably wrong about this, as the tyre would collapse. Could cause damage and air would get in again.

Exactly. Tyres are designed to work with a positive pressure. 

What I am saying is that tyres can not be fully filled with dry nitrogen.

[Alex-W]

No, but they could be filled with 2 bar of N2, meaning it's 93% Nitrogen...  then deflated to 0, then refilled taking it to 98% and repeated etc.  You can't remove 100% without pulling a vacuum but you can dilute and refill to the point that the other gasses are minimal.  I assume this is what they do?

[gregoir]

Has anyone actually seen this procedure being carried out?

And unless you get your tyre pressures checked and adjusted at a nitrogen dealer,DIY with a tyre pump will introduce more air.

Edited 19 August, 2019 by gregoir

[Ootohere]

Seen all sorts of kidology going on, and nitrogen filled tyres going down and then re-inflated by the air pump.

 

Guide dogs for the stupid are available on Ebay and also Heavy Air canisters as used to be used on Fabia to give better handling...

[KenONeill]

On 19/08/2019 at 11:58, Roottootemoot said:

Heavy Air canisters as used to be used on Fabia

Or heavy water to get more mass up the front for drag racing.  

[Ootohere]

No we used normal water of the normal weight in the old landy or dumper truck tyres. 

  Freezes though and gives a really bad balanced tyre....

 

We had no access to heavy water as the British Bombed the facilities the Germans had in Norway back in the 1940's.  

(Ah i should have watched the film Telemark again,  i liked Kirk Douglas....)

 

Maybe VW have found new old stock though, just for use with the WLTP & RDE2 

 

PS

Sorted, i will get it from Ebay.

Just need a source of light water now.

 

 

 

Edited 19 August, 2019 by Roottootemoot

[logiclee]

21 hours ago, Roottootemoot said:

 That is why a tyre pressure gauge should be in the car, 

or in your pocket when collecting hire cars, loan cars, fleet cars, cars after a service or new cars from a PDI.   People in the motor trade can kill you.

 

 

 

I took the train and collected a new Yeti from Manchester.

 

Drove it back to Nottinghamshire and it didn't feel as planted as the one on the test drive and was picking up the road imperfections.

 

When I got home I checked the pressures, should have been 32psi from memory.

 

NSF 52psi

OSF 44psi

NSR 36psi

OSR 24psi.

 

I complained to the dealer (A common one who do PCH deals) and they said they do not PDI lease vehicles at the dealership but have an offsite PDI centre.

 

That will mean they will have a minimum wage guy who's done a days course to tick some boxes and has to do 4 vehicles an hour.

[Breezy_Pete]

8 hours ago, Alex-W said:

No, but they could be filled with 2 bar of N2, meaning it's 93% Nitrogen...  then deflated to 0, then refilled taking it to 98% and repeated etc.  You can't remove 100% without pulling a vacuum but you can dilute and refill to the point that the other gasses are minimal.  I assume this is what they do?

 

I'd be utterly astonished if that's what they do. 

[Alex-W]

No idea, not something I've ever looked at having done so don't know what they do, just saying it's pretty simple to get to at least 99% nitrogen without going below atmospheric.

 

If it wasn't for the fact I'd be ridiculed by all and sundry I'd be tempted to fill a couple of wheels at work and see what difference it makes.   That and i would have to make to an adapter and I CBA.

[OldBoyScout]

This is how it's done:

 

 

He puts a bit of nitrogen into the tyre and lets it out again. Then he inflates the tyre to full pressure with the nitrogen. He ends up with just over 98% of nitrogen in the tyre, and calls it a good fill.

 

[Ootohere]

 

 

[OldBoyScout]

I watched that video too. I think most of what he says there makes sense and is correct, except nitrogen is heavier than air, not lighter.

[shyVRS245]

12 minutes ago, OldBoyScout said:

I watched that video too. I think most of what he says there makes sense and is correct, except nitrogen is heavier than air, not lighter.

Probably why hot air balloons don't use nitrogen for take off.

[OldBoyScout]

4 minutes ago, shyVRS245 said:

Probably why hot air balloons don't use nitrogen for take off.

Actually the hot air would be 78% nitrogen, but I don't think we should go any further with hot air, next thing we know someone will be bringing farts into the discussion.

 

[shyVRS245]

3 minutes ago, OldBoyScout said:

Actually the hot air would be 78% nitrogen, but I don't think we should go any further with hot air, next thing we know someone will be bringing farts into the discussion.

 

As you mention it best not to bend over release a burst of methane whilst rubbing 2 sticks together in the time honoured Boy Scout way to produce fire, or you may end up with a flame thrower.

[Breezy_Pete]

9 minutes ago, OldBoyScout said:

Actually the hot air would be 78% nitrogen, but I don't think we should go any further with hot air, next thing we know someone will be bringing farts into the discussion.

 

Doubt it; what about all the CO2 and H2O from the burner?

[OldBoyScout]

2 minutes ago, Wino said:

Doubt it; what about all the CO2 and H2O from the burner?

At the risk of bending over I bow to your superior knowledge.

[shyVRS245]

6 minutes ago, OldBoyScout said:

At the risk of bending over I bow to your superior knowledge.

Popular game in Prison or use the "Oh dear how clumsy of me I appear to have dropped the bar of soap".