[Spridgets] Air Pressure & Lug Nut Torque

bmwwxman bmwwxman at gmail.com
Tue Aug 28 20:54:13 MDT 2018


I'm thinking of using Serin in mine.....

On Tue, Aug 28, 2018 at 9:53 PM CosmicMag1380 via Spridgets <
spridgets at autox.team.net> wrote:

> 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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>> ------------------------
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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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-- 
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