[Spridgets] Air Pressure & Lug Nut Torque

[CosmicMag1380]

Hey Ron,

Is the math the same if you have nitrogen in your tires?

Montana Bob

On Tue, Aug 28, 2018 at 4:45 PM Ron Soave via Spridgets <
spridgets at autox.team.net> wrote:

> Heat. Your increased load causes heat. You want higher pressures for
> increased sidewall strength, btw. The math is simple -
>
>  PV=nRT. V is constant, so as T increases, P increases. Or, simplified,
> the density of air is
>
> 2.7*P/T. As t increases, the air expands in a given volume and pressure
> increases.
>
> Ron Soave
>
> On Aug 28, 2018, at 10:20 AM, Mike Rambour via Spridgets <
> spridgets at autox.team.net> wrote:
>
>
>  I have to partially agree.  I also have never seen the 32 degree
> specification and that would seem near impossible for any owner or even
> tire shop to check the pressure at that point (maybe a few lucky ones in
> the cold part of the country for a few months).
>
>  But Tire pressure is not the same when hot or cold, check your tire
> pressure in the morning before driving and then check it again after 10-15
> miles down the freeway and you will see it has increased.  In my new truck,
> I have tire pressure monitors, I will start at 35psi in the morning and
> average 39psi on the freeway.  Its interesting to see that the front tires
> will get to 40psi and rears stay at 39psi, but when towing  a heavy
> trailer, the rears will get to 41-42psi while the fronts stay at 39.  And
> this is always starting at 35 cold, by cold I mean mid-60's ambient
> temperature and before driving at all.  I assume the difference in PSI is
> due to weight on the tire at the time, motor up front and 1-2psi then empty
> rear of truck, towing its the other way around, more weight on the rear.
> And no, I do not use my TPM to set my tire pressure, I use a proper tire
> gauge, but the TPM is never more than 1 psi off.
>
>  Some people add PSI in the belief that they will get better mileage,
> doubt its true after a certain point.  Yes, if your tires are under
> pressured, then getting it to manufacturers specs will improve mileage (by
> what, a few tenths maybe, assuming the tires are not flat to begin with)
> but after you are in spec, I seriously doubt it will improve the mileage
> more than a tenth of a MPG.
>
>     Mike
>
>
> On 8/28/2018 5:39 AM, Rick Fisk via Spridgets wrote:
>
> Allen,
>
> Not wanting to start anything here, but your tire pressure recommendations
> don't make sense to me.  I've never seen the recommended tire pressure is
> at 32 degrees F spec in a manual anywhere.  ???  Seems to me the tire
> pressure should be the same no matter what the temperature is.
>
> For every 10 degree F rise in air temperature the pressure in your tires
> will rise about 1 psi and fall 1 psi for every 10 degree drop in
> temperature.  So to maintain the car manufacturer's recommended tire
> pressure you should reduce the pressure when the temp goes up and raise it
> when the temp drops.
>
> Why would you always add 5 psi to the recommended pressure?  Seems to me
> the car manufacturer probably knows best when it comes to recommended tire
> pressures for their cars.
>
> Rick
>
> Sent from my keyboard
>
> On Aug 27, 2018, at 10:39 AM, Allen Hefner via Spridgets <
> spridgets at autox.team.net> wrote:
>
> Don't forget that the recommended tire pressure in the manuals is at 32
> degrees. You usually add 1 PSI for every 10 degrees above freezing. Nobody
> seems to know that anymore. The manuals just say ## PSI cold. I always just
> add 5 PSI to the recommended pressure.
>
> Allen Hefner
> Norristown, PA
>
>
> --
> A gun is like a parachute, if you need one but don't have it,
> you'll probably never need one again.
>
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-- 
Kent
1960 Bugeye
1983 Garage full of spridget parts!
2010 Arrow shed full of excess spridget parts!!!
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