Nitrogen instead of compressed air
Discussion
What problem are you trying to solve?
Scientifically, rather than purely in a tyre-filling scenario...
If you're comparing completely dry gases, then there's less than 1% difference in heat-related pressure increases between compressed air and pure nitrogen.
Moisture levels would make more difference as temps rise as this will expand more than any of the other gases in there.
It might matter in Formula 1 where 1% is meaningful, but probably not in club/national racing levels.
Scientifically, rather than purely in a tyre-filling scenario...
If you're comparing completely dry gases, then there's less than 1% difference in heat-related pressure increases between compressed air and pure nitrogen.
Moisture levels would make more difference as temps rise as this will expand more than any of the other gases in there.
It might matter in Formula 1 where 1% is meaningful, but probably not in club/national racing levels.
mmm-five said:
What problem are you trying to solve?
Scientifically, rather than purely in a tyre-filling scenario...
If you're comparing completely dry gases, then there's less than 1% difference in heat-related pressure increases between compressed air and pure nitrogen.
Moisture levels would make more difference as temps rise as this will expand more than any of the other gases in there.
It might matter in Formula 1 where 1% is meaningful, but probably not in club/national racing levels.
i,m trying to find a good start point of inflation from cold, if i wanted to end up at 35psi hot what should i start with . I used to start on compressed air 22psi cold to reach 30psi hot.Scientifically, rather than purely in a tyre-filling scenario...
If you're comparing completely dry gases, then there's less than 1% difference in heat-related pressure increases between compressed air and pure nitrogen.
Moisture levels would make more difference as temps rise as this will expand more than any of the other gases in there.
It might matter in Formula 1 where 1% is meaningful, but probably not in club/national racing levels.
77racing said:
i,m trying to find a good start point of inflation from cold, if i wanted to end up at 35psi hot what should i start with . I used to start on compressed air 22psi cold to reach 30psi hot.
I think he meant, why are you switching to Nitrogen inflation rather than just using air. Although asking you to justify your decision is not particularly helpful to your quest for answers.In answer to your question, this is not really something anyone will be able to answer particularly accurately for your given situation so you will just have to test really.
Start at a good guess (slightly on the high side) then just keep bleeding air out over a 20-30 minute run till you reach a stable level of your desired hot pressure. Let them cool right down then make a note of the cold pressures and Bob’s your uncle.
Ideally use it on newly fitted tyres.
The benefit of it, to those nay sayers above, is that in many cars tyre pressures are in effect part of the combined spring rate (as the tyre compression and side wall movement allows some initially element of damping and movement before the suspension components are engaged). Also it can be desirable for example to maintain a softer tyre pressure and allow the tyre sidewall to roll and/or the contact patch to be enlarged - sidewall movement also generates heat which increased pressure and therefore reduces this element over time. Additionally where a car is running over long periods it can be advantageous to control or help to control the growth in tyre pressures over a long stint.
We use it in several of our cars and it serves a purpose.
Like everything you need to test it to see what it will do in your car but for us where as we might have seen a 6-7 psi increase cold to hot that might be reduced to 2-3 psi with Nitrogen.
The benefit of it, to those nay sayers above, is that in many cars tyre pressures are in effect part of the combined spring rate (as the tyre compression and side wall movement allows some initially element of damping and movement before the suspension components are engaged). Also it can be desirable for example to maintain a softer tyre pressure and allow the tyre sidewall to roll and/or the contact patch to be enlarged - sidewall movement also generates heat which increased pressure and therefore reduces this element over time. Additionally where a car is running over long periods it can be advantageous to control or help to control the growth in tyre pressures over a long stint.
We use it in several of our cars and it serves a purpose.
Like everything you need to test it to see what it will do in your car but for us where as we might have seen a 6-7 psi increase cold to hot that might be reduced to 2-3 psi with Nitrogen.
TimCrighton said:
Ideally use it on newly fitted tyres.
The benefit of it, to those nay sayers above, is that in many cars tyre pressures are in effect part of the combined spring rate (as the tyre compression and side wall movement allows some initially element of damping and movement before the suspension components are engaged). Also it can be desirable for example to maintain a softer tyre pressure and allow the tyre sidewall to roll and/or the contact patch to be enlarged - sidewall movement also generates heat which increased pressure and therefore reduces this element over time. Additionally where a car is running over long periods it can be advantageous to control or help to control the growth in tyre pressures over a long stint.
We use it in several of our cars and it serves a purpose.
Like everything you need to test it to see what it will do in your car but for us where as we might have seen a 6-7 psi increase cold to hot that might be reduced to 2-3 psi with Nitrogen.
Tim I take compliments and insults from those that know no better LOL, your point about stabalising pressure over a period of time is going to save a lot of faff. I was thinking that an advantage to already been at pressure from the get go would give me an advantage into the first few laps all be it heat will still take time but less to come up,using nitrogen. There is obviously an advantage other wise why would all the top teams with top cars be using it. I use 305 645 18 tyres so will as you surgest start 3 psi down and wave good bye to the nay sayers LOL The benefit of it, to those nay sayers above, is that in many cars tyre pressures are in effect part of the combined spring rate (as the tyre compression and side wall movement allows some initially element of damping and movement before the suspension components are engaged). Also it can be desirable for example to maintain a softer tyre pressure and allow the tyre sidewall to roll and/or the contact patch to be enlarged - sidewall movement also generates heat which increased pressure and therefore reduces this element over time. Additionally where a car is running over long periods it can be advantageous to control or help to control the growth in tyre pressures over a long stint.
We use it in several of our cars and it serves a purpose.
Like everything you need to test it to see what it will do in your car but for us where as we might have seen a 6-7 psi increase cold to hot that might be reduced to 2-3 psi with Nitrogen.
Tim will see you in anglesey later in the year i hope i,m using it on this LOL................................................
20200820_070241 by flat chat, on Flickr
20200820_070241 by flat chat, on Flickrliner33 said:
We used to use dry air from dive cylinders when drag racing gave more consistent results which were key when you are talking about 1/4 of a psi and less than 8 psi to start with . Easy to source also
i had thought of that and went for nitrogen because it is more stable over time. 77racing said:
Tim will see you in anglesey later in the year i hope i,m using it on this LOL................................................
20200820_070241 by flat chat, on Flickr
Love that!! It'll be exciting up through Church and School! 20200820_070241 by flat chat, on FlickrIt's still a great looking car the Sag. I nearly raced the car in period and had it not been for a last minute swap it might be a very different story. One for the bar at Anglesey!
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