What exactly does cold pressure mean?

On Dec 3, 1:21*am, charter > wrote:
> On Dec 2, 10:03*am, Tom Adams > wrote:
>
>
>
>
>
> > On Dec 2, 11:48*am, wrote:
>
> > > A nephew of mine, he drove an 18 wheeler for a while.Now he drives a
> > > tour bus/coach for Roberts company, Nashville.I reckon he knows
> > > something about tires and tire pressure.
> > > cuhulin
>
> > I get the impression that some posters are ignoring the fact that 15-
> > passenger vans only have one rear tire on each side. *Comparing these
> > to vehicles with 2 or more rear tires on each side does not make
> > sense.
>
> > This is an important factor in the rollover risk. * About 15% of fatal
> > rollovers in 15-passenger vans were initiated by a rear tire blowouts
> > or tread separation.
>
> > Fatal left-rear tire failures are more common. *15-passenger vans have
> > an aisle on the right side and the left tire ends up carrying most of
> > the weight. *Some transit operations have switched to center ailse
> > seat layouts.
>
> Well, I did post a link for the Bluebird Microbird, which comes in a
> lot of single wheel setups, as do many shuttle busses. These busses
> have even higher CG than a 15pass van, yet, most parents won't think
> twice about putting 19 of their kids in one, because it is a "school
> bus".
>
> I do agree with you that the left weight bias is a safty risk. There
> is no real easy fix, other than putting the middle 3 rows on a sliding
> track, and have them slide towards the center.
>
> Regarding tires, if they're within the load limit, and are pumped to
> 80 psi, then they should not fail. Any failure is a defect from the
> tire manufacturer, and lawsuit waiting to happen.
>
> BTW, I don't believe this 45% weight resting on left rear tire hype.
> Assume it's true, then: left rear should be around 40% by simple
> geometry, that leaves the front tires carrying 10% and 5% of the van's
> weight? Impossible, you'd catch air over a speed bump if that was the
> case.
>
> The rear tires carrying 35% / 30%, with front tires 15% and 20%, is a
> more plausible case. Even that seems exaggerated.- Hide quoted text -
>
> - Show quoted text -

I don't know what the tire weight ratios are. In a fully loaded E350
15 passenger van, you
have about 600 pounds (4 passengers) behind the rear axle that counter
balances the weight in front of the rear axle somewhat. And a full
tank of gas
adds weight (but a full tank is good in that it lowers the center of
gravity)

On Dec 1, 9:34*pm, jim beam > wrote:
> On 12/01/2010 05:51 PM, charter wrote:
>
>
>
>
>
> >> If the door decal specifies 80psi and the tire sidewall max
> >> is 80psi, I would suspect someone has installed a reduced
> >> load range tire on the van.
> >> Lugnut
>
> > Not necessarily; it's perfectly acceptable to have the sticker
> > pressure the same as max tire pressure. And this is often the case
> > when a tire is required to carry near its max capacity.
>
> > Having a "max" pressure of 80 psi does not mean the tire will blow at
> > 81 psi, or sustain damage. In fact, most tires do not blow till
> > atleast 2 - 3 times over its max pressure, sometimes up to 5 on
> > commercial H+ rated tires (500+ psi). For LT tires, 80 psi, or load E
> > rating, is the max you can go. Unless you want to convert your van to
> > 19.5" wheels and run commercial tires.
>
> > As both an engineer and commerical driver, I would say a MAJORITY of
> > 15 passenger van rollovers are the operator's fault. Most people don't
> > think twice when piloting a van carrying 3000 lbs of human cargo; they
> > accelerate, stop, and swerve the same as they would in their Accord.
> > Of course that's asking for trouble! Consider this: there're millions
> > of big rigs and commercial busses runing 100,000s miles a year out
> > there, and every singe one of them has a MUCH higher CG than even a
> > fully loaded van (think tanker, or meat truck). Should we ban all of
> > them because they're prone to roll overs?
>
> > Your typical tour coach has 10,000 lbs of people riding 6 feet off the
> > ground, with a vehicle width of only 1.5 times wider than a van. What
> > do you think would happen if the coach driver swerves or performs a
> > "fish hook manuver" at 75 mph? Truth is, bus drivers rarely have to do
> > that. If 15 passenger van drivers learn to 1) not drive so fast, and
> > 2) not follow so closely, then him or her wouldn't have to either.
>
> > The other thing is maintenance. Safety studies discovered 57% of 15
> > passenger van crashes had one or more tires severely under-inflated.
> > Is that a design flaw or driver neglegance. Since 15 pass van tires
> > are already near their max weight capacity, any underinflation is
> > fatal. I can gurantee that if every 15p van has its tires at 60 psi
> > fron / 80 psi rear, blowouts will be close to none.
>
> > The sad reality is, your typical church driver or sports coach know
> > nothing about the above, and that's why we hear these tragic stories
> > of multiple children injured or killed in 15 pass van crashes. *I'm
> > not saying the design of these vans are perfect, or even good, but
> > they're far from the death traps that media has led us into believing.
>
> no dude, they're very much death traps. *while you're right that drivers
> have a large responsibility, the drive dynamics of these things is
> abysmal. *no vehicle should roll just because of a blowout, and these
> things do. *and it's not like the market into which they're being sold
> is populated by experienced professional drivers. *if the manufacturers
> /know/ they're being sold to amateurs, and they do, they need to be
> designed [and regulated] accordingly, just like with suv's.
>
> one more thing - comparing 15p handling to a passenger coach is a flawed
> analogy - the coach handles /much/ better and has /far/ superior suspension.
>
> --
> nomina rutrum rutrum- Hide quoted text -
>
> - Show quoted text -

You have to put this death trap thing into prospective. I think are
probably about
average in terms of safety (but that is a moving target since new cars
are getting
safer each year). They have a size advantage that somewhat cancels
out the increase rollover
risk. This web site makes a good case that the Smart Car is the most
unsafe car
on the road today:

www.informedforlife.org

The NHTSA says (in the fine print) that there safety ratings should
not be used to compare
cars with more than a 250-pound difference in weight.

I do think the 15-passenger vans are one of those vehicles that punish
the owner more if they are not careful about safety-related
maintenance and other practices.

If I don't ride to work in the van, I drive a 2000 Honda CRV (our
second car) which I think is more of a death trap all things
considered. I would not buy that car today with all I know now. I
suppose our 2008 Honda Accord that has ESC is safer.

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)?
>
>
>
> > 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

The tires are LT and they are as specified on the door panel.

Goodrich tire, probably the tire that Ford delivers the van with.

But, as I mentioned, we detected a belt separation via vibration in
the steering wheel. The transit authority replaced both back tires
(with the same make and modle tire I think).

We have not been able to determine the cause of the belt separation.

It extra stresses imposed by Rollgard along with the bumpy back roads
along our route might be part of the problem.

On Dec 3, 8:05*am, Tom Adams > wrote:
*I don't think they require daylight
> running
> lights, that's the only criticism I have of them.- Hide quoted text -
>
> - Show quoted text -
____________________

I guess that's a good thing - but personally I think DRLs are a
CROCK. If you can't see a car coming in broad daylight you should be
driving(or walking along the street) you really should be going out
of the house at all!

Juss sayin..

-CC

On Dec 3, 5:29*pm, ChrisCoaster > wrote:
> On Dec 3, 8:05*am, Tom Adams > wrote:
> *I don't think they require daylight> running
> > lights, that's the only criticism I have of them.- Hide quoted text -
>
> > - Show quoted text -
>
> ____________________
>
> I guess that's a good thing - but personally I think DRLs are a
> CROCK. *If you can't see a car coming in broad daylight you should be
> driving(or walking along the street) you really should be going out
> of the house at all!
>
> Juss sayin..
>
> -CC

"Nearly all published reports indicate DRLs reduce multiple-vehicle
daytime crashes."

http://www.iihs.org/research/qanda/drl.html

On Dec 4, 7:23*am, Nancy Adams > wrote:
>
> "Nearly all published reports indicate DRLs reduce multiple-vehicle
> daytime crashes."
>
> http://www.iihs.org/research/qanda/drl.html- Hide quoted text -
>
> - Show quoted text -


http://www.x-entertainment.com/pics/kool1.jpg

"ChrisCoaster" > wrote in message
news:3339cc17-____________________

I guess that's a good thing - but personally I think DRLs are a
CROCK. If you can't see a car coming in broad daylight you should be
driving(or walking along the street) you really should be going out
of the house at all!

Juss sayin..

-********
Just because the DRL stands for "daytime" running lights, you cant
assume that you will be in "broad daylight". There are plenty of bad
driving conditions in the daytime where augmented lights should be
used. It is a law here in Texas....but people avoid it because (1)
they are poorly trained as drivers and (2) lack of enforcement make
people lax to comply.

IMO, DRL's dont hurt a thing, and in some cases they provide
valuable safety functions.

On 12/04/2010 01:33 PM, hls wrote:
>
> "ChrisCoaster" > wrote in message
> news:3339cc17-____________________
>
> I guess that's a good thing - but personally I think DRLs are a
> CROCK. If you can't see a car coming in broad daylight you should be
> driving(or walking along the street) you really should be going out
> of the house at all!
>
> Juss sayin..
>
> -********
> Just because the DRL stands for "daytime" running lights, you cant
> assume that you will be in "broad daylight". There are plenty of bad
> driving conditions in the daytime where augmented lights should be
> used. It is a law here in Texas....but people avoid it because (1)
> they are poorly trained as drivers and (2) lack of enforcement make
> people lax to comply.
>
> IMO, DRL's dont hurt a thing, and in some cases they provide
> valuable safety functions.

so... you like DRLs because people are too stupid to turn on their
headlights when they should? That doesn't make sense.

I personally *don't* like DRLs not on principle but because of their
current implementations.

1) they don't provide any conspicuity except to the front of the car.
Low beam headlights will turn on the taillights and side markers (on
cars so equipped, which is most since 1968ish) as well.

2) current US regs allow high beam headlights or turn signals to be used
for DRLs, both of which are incredibly bad ideas. High beams because of
glare; turn signals because of the possibility of signal ambiguity.

nate

--
replace "roosters" with "cox" to reply.
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Nate Nagel > wrote:
>
>so... you like DRLs because people are too stupid to turn on their
>headlights when they should? That doesn't make sense.

That makes PERFECT sense.

If I am on the road with someone who is too stupid to turn his headlights
on when he should, I would support having some goofy electronic gadget do
it for him.

Not only THAT, I would support having something that would turn on the
turn signals for him since half the stupid people on the road can't figure
those out either.

Now, from my perspective it would be better to arrest those people and
force them to take a real driving class and an aggressive safety test
before allowing them on the road. But that's not going to happen. So
having some idiotic mechanical thing do it for them is about the only
thing that will improve the situation.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 12/04/2010 03:02 PM, Scott Dorsey wrote:
> Nate > wrote:
>>
>> so... you like DRLs because people are too stupid to turn on their
>> headlights when they should? That doesn't make sense.
>
> That makes PERFECT sense.
>
> If I am on the road with someone who is too stupid to turn his headlights
> on when he should, I would support having some goofy electronic gadget do
> it for him.
>
> Not only THAT, I would support having something that would turn on the
> turn signals for him since half the stupid people on the road can't figure
> those out either.
>
> Now, from my perspective it would be better to arrest those people and
> force them to take a real driving class and an aggressive safety test
> before allowing them on the road. But that's not going to happen. So
> having some idiotic mechanical thing do it for them is about the only
> thing that will improve the situation.
> --scott

Sorry, wrong answer. Give the incompetents a choice:

1) learn to drive

2) don't drive

Driving is not a difficult task to do correctly in a non-competition,
non-inclement weather conditions. Making allowances for the
incompetents only breeds more incompetence.

nate

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replace "roosters" with "cox" to reply.
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