Tyre pressures

[Nabsim]

As far as I am aware Charles and Boyles law apply equally to nitrogen as to air, what using nitrogen does for you is reduce the water vapour so less corrosion.

So what stopped exploding tyres at high temperatures then?

 

[Nabsim]

Sorry yes, nitrogen will reduce the tyre temperature under load (or high speeds) it will also slow down passing through the carcass. And isn’t affected the same by cold temperatures (that’s the water bit maybe?)

How could I think any of the above may have bearings on tyre pressures

 

[wildebus]

As far as I am aware Charles and Boyles law apply equally to nitrogen as to air, what using nitrogen does for you is reduce the water vapour so less corrosion.

I thought the idea of using Nitrogen was to give less variance as the tyre warms up (this I think is how it is promoted by Costco at least I think?), so after reading the comment above, I did a little search on the Internet for some info and calculators ....

Found this calculator for Nitrogen - https://icemeister.net/backroom/calculators-2/nitrogen-pressure-vs-temperature-calculator
And this one for "air" - http://physics.bu.edu/~schmaltz/deflate.html . Calc references a Football, so will guess it is based on normal everyday air rather than any exotic gases

On the assumption that both calculators are correct, using Nitrogen actually makes no difference whatsoever in terms of Pressure Variation!

 

[Nabsim]

I posted directly above you Dave, it’s the speed and load but that does it not ambient. I had to have a check as I knew it cured a biggish problem we used to suffer.

 

[wildebus]

I posted directly above you Dave, it’s the speed and load but that does it not ambient. I had to have a check as I knew it cured a biggish problem we used to suffer.

I just read your reply after I posted mine.
So Nitrogen changes pressure as temp increases in the same way as air, BUT .... using nitrogen actually stops the temp variation to such a degree that the end result is a more even temperature and therefore a more even pressure in the tyre. Is that correct?

 

[Nabsim]

I just read your reply after I posted mine.
So Nitrogen changes pressure as temp increases in the same way as air, BUT .... using nitrogen actually stops the temp variation to such a degree that the end result is a more even temperature and therefore a more even pressure in the tyre. Is that correct?

That’s the way I took it. I wouldn’t have paid any extra to get the van filled with nitrogen it was a freebie I didn’t even know about until I got the invoice. I do know it stopped the truck tyres exploding on a drum used for heating stone to temperature for producing asphalt. There would be more heat in the tyre than on a van in the uk I would think as the tread got shiney while in use, bit like you see F1 tyres when heat blanket removed.

 

[in h]

Just a thought as there is some good info in this thread but it's now all jumbled up

The problem is that it is a discussion forum. People like to assert and reassert what they've been told. Even when it was wrong or misunderstood. And that's their right.
Until recently, the BBC used to always include a climate change denier in any discussion in the interests of "balance". (though never a representative of the Flat Earth Society when discussing anything to do with space).
A reference site where you get reliable information you can depend on doesn't sit comfortably on a discussion forum

 

[Nabsim]

There is a documents area on motorhomebuilder for info. In the case of tyres I prefer to use what Conti told me to anything else. From what I have seen posted around though other manufacturers may not give you ‘your’ info.

 

[Tookey]

Considering correct tyre pressures are so important from a legal, safety and environmental point I was disappointed to find nothing on the DVLA site.....unless I missed it. Will look around the net and motorhome builder

 

[mark61]

No one expects delivery drivers to adjust their pressure between loads, and the "correct" pressure can vary hugely between empty and full loaded. The correct or maybe recommended pressure could well be 45psi empty and 70+psi laden, these drivers aren't braking the law by running at 70psi empty, but probably would be if running at 45 psi fully laden.

So you have to work out tyre pressures yourself, knowing weights and tyre specs. Then you may also want to take other things into account, ie. If doing a fast drive down to the Pyrenness, toll roads or fast roads all the way, I'll choose a different pressure than I would if trundling around Poland, where I'll go for softish tyre anyday, but I also know I won't be doing motorway speeds, which in France is much faster than here

 

[Nabsim]

I use the loaded settings Conti gave me but I don’t load and unload so I doubt it would be much out. In a Moho most wont have more than 300kg difference I expect.

 

[Sid]

I thought the idea of using Nitrogen was to give less variance as the tyre warms up (this I think is how it is promoted by Costco at least I think?), so after reading the comment above, I did a little search on the Internet for some info and calculators ....

Found this calculator for Nitrogen - https://icemeister.net/backroom/calculators-2/nitrogen-pressure-vs-temperature-calculator
And this one for "air" - http://physics.bu.edu/~schmaltz/deflate.html . Calc references a Football, so will guess it is based on normal everyday air rather than any exotic gases

On the assumption that both calculators are correct, using Nitrogen actually makes no difference whatsoever in terms of Pressure Variation!

I think the big difference is that the nitrogen from a cylinder will be dry, whereas the air will have a significant amount of water included which will make a afir difference if it turns to a vapour, which maybe what was happening in Nabsim's example. I doubt many garages fit a dryer in line on their compressors. So go with your plan of sticking with Conti's pressures.

 

[wildebus]

I think the big difference is that the nitrogen from a cylinder will be dry, whereas the air will have a significant amount of water included which will make a afir difference if it turns to a vapour, which maybe what was happening in Nabsim's example. I doubt many garages fit a dryer in line on their compressors. So go with your plan of sticking with Conti's pressures.

just to say .... not MY plan (I don't agree with the idea of blindly pumping to whatever the maximum pressure quoted is)