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What exactly does cold pressure mean?



 
 
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  #11  
Old November 30th 10, 03:55 PM posted to rec.autos.tech
John S.
external usenet poster
 
Posts: 981
Default What exactly does cold pressure mean?

On Nov 29, 3:26*pm, Tom Adams > wrote:
> I help maintain a Ford E350 used for a vanpool.
>
> The door panel spec says that the rear tires require 80 psi.
>
> The sidewall specs on the rear tires say that the maximum pressure is
> 80 psi.
>
> So, what does cold pressure mean exactly?
>
> If I check the tires on a cold morning (say 35 degrees) I will end up
> putting in a few extra pounds more that I would at 70 degrees. * But I
> bet the operating temperature of a tire is largely independent of
> whether the ambient temperature is 35 or 70.


Does the door panel actually say 80 psi is the REQUIRED pressure? Or
is it the maximum pressure with the recommended pressure something
closer to 60 psi?
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  #12  
Old November 30th 10, 05:24 PM posted to rec.autos.tech
Tom Adams
external usenet poster
 
Posts: 85
Default What exactly does cold pressure mean?

On Nov 29, 4:52*pm, "hls" > wrote:
> "Tom Adams" > wrote in message
>
> ...
> On Nov 29, 4:12 pm, "hls" > wrote:
>
>
>
>
>
> > "Tom Adams" > wrote in message

>
> ....

>
> > >I help maintain a Ford E350 used for a vanpool.

>
> > > The door panel spec says that the rear tires require 80 psi.

>
> > > The sidewall specs on the rear tires say that the maximum pressure is
> > > 80 psi.

>
> > > So, what does cold pressure mean exactly?

>
> > > If I check the tires on a cold morning (say 35 degrees) I will end up
> > > putting in a few extra pounds more that I would at 70 degrees. But I
> > > bet the operating temperature of a tire is largely independent of
> > > whether the ambient temperature is 35 or 70.

>
> > The difference in pressure between 35F and 70F is no more than about
> > 3-4 psi.

>
> > The "cold" pressure to be that which is measured on a tire which is
> > has not been heated by road use. It is the ambiental temperature
> > whether it is 35F or 70F.

>
> Seems like that 3-4 psi would lead to a higher operating temperature
> and pressure
> when you got up to speed and fully warmed up the tire. Correct?
>
> Are you saying that should be ignored even when you are operating at
> the
> maximum pressure specified on the tire wall?
>
> I didnt say you should ignore anything.
> If the tire is specified at 80 psi max COLD, then that is what it means.
> The pressure will rise as the tire heats up, but then that is not a cold
> pressure reading.
>
> If you are going to be on the highway, then you can stop and measure
> the hot pressure when you fuel. *You can reduce them to 80PSI if
> you tire says 80psi maximum pressure.- Hide quoted text -
>
> - Show quoted text -


If I set them to 80 cold, then they are around 84 after highway
driving.
  #13  
Old November 30th 10, 06:23 PM posted to rec.autos.tech
Tom Adams
external usenet poster
 
Posts: 85
Default What exactly does cold pressure mean?

On Nov 29, 10:57*pm, jim beam > wrote:
> On 11/29/2010 06:57 PM, Steve W. wrote:
>
> > Tom Adams wrote:
> >> I help maintain a Ford E350 used for a vanpool.

>
> >> The door panel spec says that the rear tires require 80 psi.

>
> > That is great IF the tires on the van are the same ones that came from
> > the factory. Otherwise it's basically crap.

>
> well, it might be crap for the tire, but it's not for the van's
> stability. *you certainly don't want the pressure to be less than that
> if it's loaded - and vanpools usually are.
>
>
>
>
>
>
>
> >> The sidewall specs on the rear tires say that the maximum pressure is
> >> 80 psi.

>
> > And what does the chart for that tire say the operating pressure should
> > be given the load you carry? If your not driving around at the GVW all
> > day then you probably also don't need the maximum pressure.

>
> >> So, what does cold pressure mean exactly?

>
> > Cold pressure means NO drive time on the tire. What it reads after the
> > van has sat long enough for the tires to reach ambient air temperature.
> > So you come out in the AM, Start the engine so it warms up and check the
> > tire air pressure. (Don't forget to check the spare)

>
> >> If I check the tires on a cold morning (say 35 degrees) I will end up
> >> putting in a few extra pounds more that I would at 70 degrees. * But I
> >> bet the operating temperature of a tire is largely independent of
> >> whether the ambient temperature is 35 or 70.

>
> > That is why you check the pressure at whatever the "normal" temp is for
> > the given season. So if you normally see 35-40 degrees during the winter
> > check it at 37 degrees. The small amount of change won't make much
> > difference.

>
> > Same in the spring and summer. If the "normal" temps are around 80
> > degrees then check it at that temp.

>
> --
> nomina rutrum rutrum- Hide quoted text -
>
> - Show quoted text -


I think I will thicken the plot a bit.

We recently had a bumpy feel in the steering wheel. The mechanics
found a "broken belt" in the left rear (probably just a separated
belt, but I did not get to eyeball it). Since then I have been
trying to figure out any possible causal factors. None of the van
drivers recall hitting a pothole at high speed.

I had been checking the tires in the morning before the van was
driven, noting the pressure differential, and then adjusting the
pressure later in the day using the differentials.

I plan to start checking pressure at something closer to average
ambient, rather than the morning temperature. That will probably
knock a pound or two off the maximum pressure when the van is in
operation.

This van has also has something called Rollgard

http://www.amtechsprings.net/portal/

I would call Rollgard a spring stiffener but "Rollgard is not a spring
stiffener" seems to be Rollgard's defacto motto ;-)

I personally think Rollgard is a sick joke. There is no testing
data. I read that they tried to get NHTSA to test it but were
declined. All they have are testimonial letters on their web site,
some of which are laughable. One says Rollgard shortens the turning
radius! Rollgard makes drivers feel better because they detect less
sway in turns, I think. I don't know if that translates into more or
less safety.

Anyway, I now have a theory that Rollgard is a tire belt breaker.
Makes sense that it would increase the forces on a tire on the bumpy
rural roads that we drive on part of our route.

Also, I think putting Rollgard on a vehicle makes it harder to sue
Ford in the case of a rollover. But this is a conversion van anyway,
so that might also make it harder.

I think these vans have about average safety overall because of the
size advantage, but they are one of most (if not he most) rollover-
prone vehicles still made. I think Ford may be paying up for
rollovers since they lost a suit a few years ago that left the judge
foaming at the mouth at Ford's practices.

Equipping a E350 with Rollgard probably makes it harder to extract
money from Ford in the case of a rollover or other design-related
failure.

And, left rear blowouts often lead to fatal rollovers in the E350.

BTW, the NHTSA says to use the door panel pressure. 80 psi in the
rear tires is probably about right when the van in close to fully
loaded:

http://www.nhtsa.gov/cars/problems/s...sumerPiece.pdf

I don't think the van has sub-standard tires, but I will double-check
that.
  #14  
Old November 30th 10, 08:04 PM posted to rec.autos.tech
Tom Adams
external usenet poster
 
Posts: 85
Default What exactly does cold pressure mean?

On Nov 29, 5:24*pm, Tegger > wrote:
> Tom Adams > wrote in news:2438871f-28ff-443d-ab57-
> :
>
> > I help maintain a Ford E350 used for a vanpool.

>
> > The door panel spec says that the rear tires require 80 psi.

>
> > The sidewall specs on the rear tires say that the maximum pressure is
> > 80 psi.

>
> > So, what does cold pressure mean exactly?

>
> Ambient temperature, or estimated middle of an ambient range.
>
> I'm wondering if those tires are correct for the vehicle. Seems to me that
> you ought to be running tires with a max pressure of more like 100 psi, to
> allow for seasonal changes in ambient.
>
> Are these truck tires (LT instead of P)?


I will double-check, but I think the tires are within specs. And, I
think the
orginal tires had an 80 psi limit. Our van pool drove 2 2009 models
during 2010 and
all the tires had that rating. They were not perfectly new, but I am
assuming that
the conversion van company and the State of NC did not switch out the
tires that Ford
put on these vans. I have not found a 15-passenger van with tires
with a higher rating.

I think the real problem is that the Ford E350 passenger van has a
flawed design.

>
>
>
> > If I check the tires on a cold morning (say 35 degrees) I will end up
> > putting in a few extra pounds more that I would at 70 degrees.

>
> That's correct. You're supposed to adjust the cold temperatures regularly,
> as ambient changes with the seasons, adding or bleeding-off as needed.
>
> Roughly, every 10F in ambient temperature changes tire pressures by 1 psi,
> up and down. Since ambient won't ever be exactly the same all the time, *
> you guess the average ambient temperature range for your time of year in
> your area, then set cold-pressure tire pressures for the middle of that
> range.
>
> Suppose ambient tends to be between 20F and 40F. You'd set the pressures to
> be 80 psi at 30F. At 20F, you're 1 psi underinflated, and at 40F, you're 1
> psi overinflated.
>
> If you happened to check the pressures when the ambient was at its high of
> 40, you would need to make sure the tire read 81 psi, so that it would be
> 80 when ambient dropped to 30, or 79 when it dropped to 20.
>
> > *But I
> > bet the operating temperature of a tire is largely independent of
> > whether the ambient temperature is 35 or 70.

>
> Probably is, but it's still starting from that cold-pressure setting. And
> an underinflated tire is going to generate a lot more heat at 90F than it
> would at 20F, even with the same number of psi underinflation.
>
> --
> Tegger


  #15  
Old November 30th 10, 08:37 PM posted to rec.autos.tech
Tom Adams
external usenet poster
 
Posts: 85
Default What exactly does cold pressure mean?

On Nov 30, 9:55*am, "John S." > wrote:
> On Nov 29, 3:26*pm, Tom Adams > wrote:
>
> > I help maintain a Ford E350 used for a vanpool.

>
> > The door panel spec says that the rear tires require 80 psi.

>
> > The sidewall specs on the rear tires say that the maximum pressure is
> > 80 psi.

>
> > So, what does cold pressure mean exactly?

>
> > If I check the tires on a cold morning (say 35 degrees) I will end up
> > putting in a few extra pounds more that I would at 70 degrees. * But I
> > bet the operating temperature of a tire is largely independent of
> > whether the ambient temperature is 35 or 70.

>
> Does the door panel actually say 80 psi is the REQUIRED pressure? *Or
> is it the maximum pressure with the recommended pressure something
> closer to 60 psi?


It's the recommended presssure in the rear tires. The recommended
pressure
in the front tires is 60 psi.

The Ford E350 is a weird vehicle.
  #16  
Old November 30th 10, 08:48 PM posted to rec.autos.tech
jim beam[_4_]
external usenet poster
 
Posts: 3,204
Default What exactly does cold pressure mean?

On 11/30/2010 09:23 AM, Tom Adams wrote:
> On Nov 29, 10:57�pm, jim > wrote:
>> On 11/29/2010 06:57 PM, Steve W. wrote:
>>
>>> Tom Adams wrote:
>>>> I help maintain a Ford E350 used for a vanpool.

>>
>>>> The door panel spec says that the rear tires require 80 psi.

>>
>>> That is great IF the tires on the van are the same ones that came from
>>> the factory. Otherwise it's basically crap.

>>
>> well, it might be crap for the tire, but it's not for the van's
>> stability. �you certainly don't want the pressure to be less than that
>> if it's loaded - and vanpools usually are.
>>
>>
>>
>>
>>
>>
>>
>>>> The sidewall specs on the rear tires say that the maximum pressure is
>>>> 80 psi.

>>
>>> And what does the chart for that tire say the operating pressure should
>>> be given the load you carry? If your not driving around at the GVW all
>>> day then you probably also don't need the maximum pressure.

>>
>>>> So, what does cold pressure mean exactly?

>>
>>> Cold pressure means NO drive time on the tire. What it reads after the
>>> van has sat long enough for the tires to reach ambient air temperature.
>>> So you come out in the AM, Start the engine so it warms up and check the
>>> tire air pressure. (Don't forget to check the spare)

>>
>>>> If I check the tires on a cold morning (say 35 degrees) I will end up
>>>> putting in a few extra pounds more that I would at 70 degrees. � But I
>>>> bet the operating temperature of a tire is largely independent of
>>>> whether the ambient temperature is 35 or 70.

>>
>>> That is why you check the pressure at whatever the "normal" temp is for
>>> the given season. So if you normally see 35-40 degrees during the winter
>>> check it at 37 degrees. The small amount of change won't make much
>>> difference.

>>
>>> Same in the spring and summer. If the "normal" temps are around 80
>>> degrees then check it at that temp.

>>
>> --
>> nomina rutrum rutrum- Hide quoted text -
>>
>> - Show quoted text -

>
> I think I will thicken the plot a bit.
>
> We recently had a bumpy feel in the steering wheel. The mechanics
> found a "broken belt" in the left rear (probably just a separated
> belt, but I did not get to eyeball it). Since then I have been
> trying to figure out any possible causal factors. None of the van
> drivers recall hitting a pothole at high speed.
>
> I had been checking the tires in the morning before the van was
> driven, noting the pressure differential, and then adjusting the
> pressure later in the day using the differentials.
>
> I plan to start checking pressure at something closer to average
> ambient, rather than the morning temperature. That will probably
> knock a pound or two off the maximum pressure when the van is in
> operation.
>
> This van has also has something called Rollgard
>
> http://www.amtechsprings.net/portal/
>
> I would call Rollgard a spring stiffener but "Rollgard is not a spring
> stiffener" seems to be Rollgard's defacto motto ;-)


the reason it's not a "spring stiffener" is that the two moving arms on
each end allow it to float. but that also means the thing is doing
absolutely nothing unless one of those ends bottoms against something.
bottom line, you're just carrying extra weight and potentially rubbing
fatigue initiation points into your real springs - i'd get rid of it
immediately.



>
> I personally think Rollgard is a sick joke. There is no testing
> data. I read that they tried to get NHTSA to test it but were
> declined. All they have are testimonial letters on their web site,
> some of which are laughable. One says Rollgard shortens the turning
> radius! Rollgard makes drivers feel better because they detect less
> sway in turns, I think. I don't know if that translates into more or
> less safety.
>
> Anyway, I now have a theory that Rollgard is a tire belt breaker.
> Makes sense that it would increase the forces on a tire on the bumpy
> rural roads that we drive on part of our route.
>
> Also, I think putting Rollgard on a vehicle makes it harder to sue
> Ford in the case of a rollover. But this is a conversion van anyway,
> so that might also make it harder.
>
> I think these vans have about average safety overall because of the
> size advantage, but they are one of most (if not he most) rollover-
> prone vehicles still made. I think Ford may be paying up for
> rollovers since they lost a suit a few years ago that left the judge
> foaming at the mouth at Ford's practices.
>
> Equipping a E350 with Rollgard probably makes it harder to extract
> money from Ford in the case of a rollover or other design-related
> failure.
>
> And, left rear blowouts often lead to fatal rollovers in the E350.
>
> BTW, the NHTSA says to use the door panel pressure. 80 psi in the
> rear tires is probably about right when the van in close to fully
> loaded:
>
> http://www.nhtsa.gov/cars/problems/s...sumerPiece.pdf
>
> I don't think the van has sub-standard tires, but I will double-check
> that.


all tires are /not/ created equal. get the best quality tires for this
thing - you have multiple lives at stake - especially if you have a rear
blowout and this thing becomes unstable and rolls. commuter vans are
terrible in the rollover stability department.


--
nomina rutrum rutrum
  #17  
Old November 30th 10, 08:50 PM posted to rec.autos.tech
jim beam[_4_]
external usenet poster
 
Posts: 3,204
Default What exactly does cold pressure mean?

On 11/30/2010 11:37 AM, Tom Adams wrote:
> On Nov 30, 9:55�am, "John > wrote:
>> On Nov 29, 3:26�pm, Tom > wrote:
>>
>>> I help maintain a Ford E350 used for a vanpool.

>>
>>> The door panel spec says that the rear tires require 80 psi.

>>
>>> The sidewall specs on the rear tires say that the maximum pressure is
>>> 80 psi.

>>
>>> So, what does cold pressure mean exactly?

>>
>>> If I check the tires on a cold morning (say 35 degrees) I will end up
>>> putting in a few extra pounds more that I would at 70 degrees. � But I
>>> bet the operating temperature of a tire is largely independent of
>>> whether the ambient temperature is 35 or 70.

>>
>> Does the door panel actually say 80 psi is the REQUIRED pressure? �Or
>> is it the maximum pressure with the recommended pressure something
>> closer to 60 psi?

>
> It's the recommended presssure in the rear tires. The recommended
> pressure
> in the front tires is 60 psi.
>
> The Ford E350 is a weird vehicle.


it's also cheap, nasty and built by frod. the exploder fiasco shows
frod will simply disregard safety if there's money to be made.


--
nomina rutrum rutrum
  #18  
Old November 30th 10, 08:53 PM posted to rec.autos.tech
jim beam[_4_]
external usenet poster
 
Posts: 3,204
Default What exactly does cold pressure mean?

On 11/30/2010 11:04 AM, Tom Adams wrote:
> On Nov 29, 5:24�pm, > wrote:
>> Tom > wrote in news:2438871f-28ff-443d-ab57-
>> :
>>
>>> I help maintain a Ford E350 used for a vanpool.

>>
>>> The door panel spec says that the rear tires require 80 psi.

>>
>>> The sidewall specs on the rear tires say that the maximum pressure is
>>> 80 psi.

>>
>>> So, what does cold pressure mean exactly?

>>
>> Ambient temperature, or estimated middle of an ambient range.
>>
>> I'm wondering if those tires are correct for the vehicle. Seems to me that
>> you ought to be running tires with a max pressure of more like 100 psi, to
>> allow for seasonal changes in ambient.
>>
>> Are these truck tires (LT instead of P)?

>
> I will double-check, but I think the tires are within specs. And, I
> think the
> orginal tires had an 80 psi limit. Our van pool drove 2 2009 models
> during 2010 and
> all the tires had that rating. They were not perfectly new, but I am
> assuming that
> the conversion van company and the State of NC did not switch out the
> tires that Ford
> put on these vans. I have not found a 15-passenger van with tires
> with a higher rating.


you don't need a higher rating - just one that doesn't fall apart /at/
that rating. what do michelin offer in your size?


>
> I think the real problem is that the Ford E350 passenger van has a
> flawed design.


well, it's a design that doesn't safely address the inevitability of
tire failure, that's for sure. best fit tires with the lowest possible
failure rate.


>
>>
>>
>>
>>> If I check the tires on a cold morning (say 35 degrees) I will end up
>>> putting in a few extra pounds more that I would at 70 degrees.

>>
>> That's correct. You're supposed to adjust the cold temperatures regularly,
>> as ambient changes with the seasons, adding or bleeding-off as needed.
>>
>> Roughly, every 10F in ambient temperature changes tire pressures by 1 psi,
>> up and down. Since ambient won't ever be exactly the same all the time, �
>> you guess the average ambient temperature range for your time of year in
>> your area, then set cold-pressure tire pressures for the middle of that
>> range.
>>
>> Suppose ambient tends to be between 20F and 40F. You'd set the pressures to
>> be 80 psi at 30F. At 20F, you're 1 psi underinflated, and at 40F, you're 1
>> psi overinflated.
>>
>> If you happened to check the pressures when the ambient was at its high of
>> 40, you would need to make sure the tire read 81 psi, so that it would be
>> 80 when ambient dropped to 30, or 79 when it dropped to 20.
>>
>>> �But I
>>> bet the operating temperature of a tire is largely independent of
>>> whether the ambient temperature is 35 or 70.

>>
>> Probably is, but it's still starting from that cold-pressure setting. And
>> an underinflated tire is going to generate a lot more heat at 90F than it
>> would at 20F, even with the same number of psi underinflation.
>>
>> --
>> Tegger

>



--
nomina rutrum rutrum
  #19  
Old November 30th 10, 09:07 PM posted to rec.autos.tech
Steve W.[_6_]
external usenet poster
 
Posts: 1,161
Default What exactly does cold pressure mean?

Tom Adams wrote:
> On Nov 29, 10:57 pm, jim beam > wrote:
>> On 11/29/2010 06:57 PM, Steve W. wrote:
>>
>>> Tom Adams wrote:
>>>> I help maintain a Ford E350 used for a vanpool.
>>>> The door panel spec says that the rear tires require 80 psi.
>>> That is great IF the tires on the van are the same ones that came from
>>> the factory. Otherwise it's basically crap.

>> well, it might be crap for the tire, but it's not for the van's
>> stability. you certainly don't want the pressure to be less than that
>> if it's loaded - and vanpools usually are.
>>
>>
>>
>>
>>
>>
>>
>>>> The sidewall specs on the rear tires say that the maximum pressure is
>>>> 80 psi.
>>> And what does the chart for that tire say the operating pressure should
>>> be given the load you carry? If your not driving around at the GVW all
>>> day then you probably also don't need the maximum pressure.
>>>> So, what does cold pressure mean exactly?
>>> Cold pressure means NO drive time on the tire. What it reads after the
>>> van has sat long enough for the tires to reach ambient air temperature.
>>> So you come out in the AM, Start the engine so it warms up and check the
>>> tire air pressure. (Don't forget to check the spare)
>>>> If I check the tires on a cold morning (say 35 degrees) I will end up
>>>> putting in a few extra pounds more that I would at 70 degrees. But I
>>>> bet the operating temperature of a tire is largely independent of
>>>> whether the ambient temperature is 35 or 70.
>>> That is why you check the pressure at whatever the "normal" temp is for
>>> the given season. So if you normally see 35-40 degrees during the winter
>>> check it at 37 degrees. The small amount of change won't make much
>>> difference.
>>> Same in the spring and summer. If the "normal" temps are around 80
>>> degrees then check it at that temp.

>> --
>> nomina rutrum rutrum- Hide quoted text -
>>
>> - Show quoted text -

>
> I think I will thicken the plot a bit.
>
> We recently had a bumpy feel in the steering wheel. The mechanics
> found a "broken belt" in the left rear (probably just a separated
> belt, but I did not get to eyeball it). Since then I have been
> trying to figure out any possible causal factors. None of the van
> drivers recall hitting a pothole at high speed.
>
> I had been checking the tires in the morning before the van was
> driven, noting the pressure differential, and then adjusting the
> pressure later in the day using the differentials.
>
> I plan to start checking pressure at something closer to average
> ambient, rather than the morning temperature. That will probably
> knock a pound or two off the maximum pressure when the van is in
> operation.
>
> This van has also has something called Rollgard
>
> http://www.amtechsprings.net/portal/
>
> I would call Rollgard a spring stiffener but "Rollgard is not a spring
> stiffener" seems to be Rollgard's defacto motto ;-)
>
> I personally think Rollgard is a sick joke. There is no testing
> data. I read that they tried to get NHTSA to test it but were
> declined. All they have are testimonial letters on their web site,
> some of which are laughable. One says Rollgard shortens the turning
> radius! Rollgard makes drivers feel better because they detect less
> sway in turns, I think. I don't know if that translates into more or
> less safety.
>
> Anyway, I now have a theory that Rollgard is a tire belt breaker.
> Makes sense that it would increase the forces on a tire on the bumpy
> rural roads that we drive on part of our route.
>
> Also, I think putting Rollgard on a vehicle makes it harder to sue
> Ford in the case of a rollover. But this is a conversion van anyway,
> so that might also make it harder.
>
> I think these vans have about average safety overall because of the
> size advantage, but they are one of most (if not he most) rollover-
> prone vehicles still made. I think Ford may be paying up for
> rollovers since they lost a suit a few years ago that left the judge
> foaming at the mouth at Ford's practices.
>
> Equipping a E350 with Rollgard probably makes it harder to extract
> money from Ford in the case of a rollover or other design-related
> failure.
>
> And, left rear blowouts often lead to fatal rollovers in the E350.
>
> BTW, the NHTSA says to use the door panel pressure. 80 psi in the
> rear tires is probably about right when the van in close to fully
> loaded:
>
> http://www.nhtsa.gov/cars/problems/s...sumerPiece.pdf
>
> I don't think the van has sub-standard tires, but I will double-check
> that.



Read the web site. Regardless of what they call it that is nothing more
than a helper spring. BUT it looks like it's a composite type so it
likely doesn't have a lot of power.

ALL vans and large vehicles are top heavy, They are ALL prone to roll
over if they are not driven properly.
The main reason why all of these vehicles are rolling over has to do
with a lack of respect of the operator for the vehicles limits.

Take a Jeep CJ. You can take them off road and darn near climb trees and
they won't roll over. Side hills are not a problem IF YOU GO SLOw. When
they came out they were popular with drivers who had used them in combat
and who respected they way they handled. The next generation was raised
with them and were taught how they should be driven, BUT they didn't buy
a lot of them when the older ones started failing. They wanted
B I G G E R vehicles and moved to large cars and wagons. Their kids
didn't get taught on narrow wheelbase vehicles, they were taught on huge
land yachts that wouldn't roll over unless you were really stupid. So
those kids and their parents more or less forgot how to deal with the
smaller vehicles.
So did their kids.
Then 4X4s became popular again. What happens? These folks who had never
though about vehicle dynamics bought up a ton of Jeeps, Small SUVs, Vans
and figured that they could drive them just like they did the cars they
had before. WRONG. They are not meant to be driven down a twisty road at
60 mph and tossed into corners like a car.

End result, They roll over. Then these folks complain about it and the
media (who were raised the same way) think that the problem is in the
vehicles design. The truth is that most of the people who roll vehicles
shouldn't be driving that type of vehicle in the first place.

But since pointing a finger at the person and saying "You're an idiot
for driving that way" is no longer an acceptable thing to do and
personal responsibility is a forgotten concept, it's so much easier to
say "It's (name company with money) fault, they made (insert product
being used by an idiot here)"

Think about this one.
Everyone makes fun of the stickers that say things like
"Do not use in the shower/bath" stuck on a hair drier or curling iron
that is wall powered. Many look at that and say DUH! Who would be dumb
enough to do that, it's just common sense.
That sticker wouldn't be there if that didn't happen at some point and a
Judge and jury decided that the company that made it was at fault for
not warning the user about that very danger!!!

Go take a look at the visor warning tags that have to be on every 4X4
and SUV now. The ones that warn you that these vehicles handle different
and that you have to be careful. Care to guess why they are there?


How about that maximum pressure warning on those tires. Think it is
there because the maker got sued at one time because Billy Bob decided
that 80 PSI just wasn't enough and tried to put 120 PSI in them "Like a
REAL TRUCK TIRE"

--
Steve W.
  #20  
Old November 30th 10, 09:14 PM posted to rec.autos.tech
Tom Adams
external usenet poster
 
Posts: 85
Default What exactly does cold pressure mean?

On Nov 30, 2:53*pm, jim beam > wrote:
> On 11/30/2010 11:04 AM, Tom Adams wrote:
>
>
>
>
>
> > On Nov 29, 5:24 pm, > *wrote:
> >> Tom > *wrote in news:2438871f-28ff-443d-ab57-
> >> :

>
> >>> I help maintain a Ford E350 used for a vanpool.

>
> >>> The door panel spec says that the rear tires require 80 psi.

>
> >>> The sidewall specs on the rear tires say that the maximum pressure is
> >>> 80 psi.

>
> >>> So, what does cold pressure mean exactly?

>
> >> Ambient temperature, or estimated middle of an ambient range.

>
> >> I'm wondering if those tires are correct for the vehicle. Seems to me that
> >> you ought to be running tires with a max pressure of more like 100 psi, to
> >> allow for seasonal changes in ambient.

>
> >> Are these truck tires (LT instead of P)?

>
> > I will double-check, but I think the tires are within specs. *And, I
> > think the
> > orginal tires had an 80 psi limit. *Our van pool drove 2 2009 models
> > during 2010 and
> > all the tires had that rating. *They were not perfectly new, but I am
> > assuming that
> > the conversion van company and the State of NC did not switch out the
> > tires that Ford
> > put on these vans. *I have not found a 15-passenger van with tires
> > with a higher rating.

>
> you don't need a higher rating - just one that doesn't fall apart /at/
> that rating. *what do michelin offer in your size?


Michelin is probably a good suggestion. There is a van that parks
near
the one I drive that has Michelin's. The tires on that van are rated
at 80 psi max, BTW.

However, I don't think I could get the transit authority to change
their
tire buying policies. I could suggest that.

The NHTSA puts out advisories on these vans, but they have never
recommended
higher standards for tires. They do have a recommendation for
replacing older
tires even when they have tread, but that was not the problem on our
2009 van.

>
>
>
> > I think the real problem is that the Ford E350 passenger van has a
> > flawed design.

>
> well, it's a design that doesn't safely address the inevitability of
> tire failure, that's for sure. *best fit tires with the lowest possible
> failure rate.
>
>
>
>
>
>
>
> >>> If I check the tires on a cold morning (say 35 degrees) I will end up
> >>> putting in a few extra pounds more that I would at 70 degrees.

>
> >> That's correct. You're supposed to adjust the cold temperatures regularly,
> >> as ambient changes with the seasons, adding or bleeding-off as needed.

>
> >> Roughly, every 10F in ambient temperature changes tire pressures by 1 psi,
> >> up and down. Since ambient won't ever be exactly the same all the time,
> >> you guess the average ambient temperature range for your time of year in
> >> your area, then set cold-pressure tire pressures for the middle of that
> >> range.

>
> >> Suppose ambient tends to be between 20F and 40F. You'd set the pressures to
> >> be 80 psi at 30F. At 20F, you're 1 psi underinflated, and at 40F, you're 1
> >> psi overinflated.

>
> >> If you happened to check the pressures when the ambient was at its high of
> >> 40, you would need to make sure the tire read 81 psi, so that it would be
> >> 80 when ambient dropped to 30, or 79 when it dropped to 20.

>
> >>> But I
> >>> bet the operating temperature of a tire is largely independent of
> >>> whether the ambient temperature is 35 or 70.

>
> >> Probably is, but it's still starting from that cold-pressure setting. And
> >> an underinflated tire is going to generate a lot more heat at 90F than it
> >> would at 20F, even with the same number of psi underinflation.

>
> >> --
> >> Tegger

>
> --
> nomina rutrum rutrum- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -


 




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