Spare Tire Question

On Mon, 22 Nov 2010 14:30:08 -0700, AJL wrote:

> Ashton Crusher > wrote:
>
>>If it exploded there was something wrong with the tire
>
> Maybe, but I think it's unlikely that I had 2 bad tires in a row. The
> first spare tire was brand new and came with my new 95 Taurus. The
> second was a used tire bought to replace it. Never had a third but by
> then I had started leaving the spare under-inflated.
>
>>or you are putting it in place with little or no air in it and then pumping it up
>>and forcing the sidewall against something sharp that cuts it.
>
> Nope.
>
>>The tires on the car get far hotter then the one sitting in the trunk
>
> Tires sitting on a parked car would be at or near the local
> air/surface temperature. Rolling tires would also be air cooled as
> well as road cooled. Neither gets as hot as the inside of a trunk (or
> passengers compartment) on a hot AZ summer day.
>
>>and they don't explode.
>
> Of course overheated tires explode, it's called a blowout. But in most
> cases rolling tire heat is caused by tire flexing due to
> under-inflation.
>
>>I"ve lived in Phx my whole life and have never
>>had a tire explode in the trunk, even really really old tires pumped
>>up to 40 psi cold.
>
> And we're supposed to pay attention to someone who lives in a hostile
> tire climate and touts using really really old over-inflated spare
> tires??

You need to look for another reason.

jim beam > wrote:

>i don't think so.

Yup, just made that **** up.

>that is true. foot pumps are reliable and cheap and work even if your
>car's battery is dead.

Damn, blown tire and dead battery at the same time. Maybe you should
invest in AAA. But no with your luck your cell phone would be likely
dead too...

"Ashton Crusher" > wrote in message
...
> If it exploded there was something wrong with the tire or you are
> putting it in place with little or no air in it and then pumping it up
> and forcing the sidewall against something sharp that cuts it.

My doughnut tire has an inflation pressure of 60 psig. In Arizona this
past summer,
as we passed through, the air temperature was 110F. The radiant heat in
the
trunk may have caused the temperature to rise much much hotter.

Now, I dont know what these are rated, but I can see that the pressure could
increase
a good bit. Gas law calculations will tell you how much, roughly.

I did not have an in-trunk blowout.. But if the poster said he did,then most
likely
he did.

"AJL" > wrote in message

> Damn, blown tire and dead battery at the same time. Maybe you should
> invest in AAA. But no with your luck your cell phone would be likely
> dead too...

You have learned about the infamous jim beam.. More sound than
fury.

On 11/22/2010 01:55 PM, AJL wrote:
> jim > wrote:
>
>> i don't think so.
>
> Yup, just made that **** up.

so how many windows did they blow out?


>
>> that is true. foot pumps are reliable and cheap and work even if your
>> car's battery is dead.
>
> Damn, blown tire and dead battery at the same time. Maybe you should
> invest in AAA. But no with your luck your cell phone would be likely
> dead too...


--
nomina rutrum rutrum

On 11/22/2010 01:51 PM, Bret wrote:
> On Mon, 22 Nov 2010 14:30:08 -0700, AJL wrote:
>
>> Ashton > wrote:
>>
>>> If it exploded there was something wrong with the tire
>>
>> Maybe, but I think it's unlikely that I had 2 bad tires in a row. The
>> first spare tire was brand new and came with my new 95 Taurus. The
>> second was a used tire bought to replace it. Never had a third but by
>> then I had started leaving the spare under-inflated.
>>
>>> or you are putting it in place with little or no air in it and then pumping it up
>>> and forcing the sidewall against something sharp that cuts it.
>>
>> Nope.
>>
>>> The tires on the car get far hotter then the one sitting in the trunk
>>
>> Tires sitting on a parked car would be at or near the local
>> air/surface temperature. Rolling tires would also be air cooled as
>> well as road cooled. Neither gets as hot as the inside of a trunk (or
>> passengers compartment) on a hot AZ summer day.
>>
>>> and they don't explode.
>>
>> Of course overheated tires explode, it's called a blowout. But in most
>> cases rolling tire heat is caused by tire flexing due to
>> under-inflation.
>>
>>> I"ve lived in Phx my whole life and have never
>>> had a tire explode in the trunk, even really really old tires pumped
>>> up to 40 psi cold.
>>
>> And we're supposed to pay attention to someone who lives in a hostile
>> tire climate and touts using really really old over-inflated spare
>> tires??
>
> You need to look for another reason.

of course. cuts, bad valves, etc. when a healthy tire is inflated
until it blows, it's a really serious BANG.

http://www.youtube.com/watch?v=k3kq8iBkdoc


--
nomina rutrum rutrum

On Mon, 22 Nov 2010 17:38:33 -0600, "hls" > wrote:

>
>"Ashton Crusher" > wrote in message
.. .
>> If it exploded there was something wrong with the tire or you are
>> putting it in place with little or no air in it and then pumping it up
>> and forcing the sidewall against something sharp that cuts it.
>
>My doughnut tire has an inflation pressure of 60 psig. In Arizona this
>past summer,
>as we passed through, the air temperature was 110F. The radiant heat in
>the
>trunk may have caused the temperature to rise much much hotter.
>
>Now, I dont know what these are rated, but I can see that the pressure could
>increase
>a good bit. Gas law calculations will tell you how much, roughly.
>
>I did not have an in-trunk blowout.. But if the poster said he did,then most
>likely
>he did.

I don't doubt his tires "blew up". What I doubt is that his claim
that all the perfectly good tires in trunks in hot climates are in
danger of "blowing up". Only a damaged or defective stationary tire
is going to blow up because the pressure went from 32 (at 80 degrees)
to 39 psi (at 150 degrees) (1 psi per 10 degree rise in temperature).

On Mon, 22 Nov 2010 20:51:17 -0800, jim beam > wrote:

>On 11/22/2010 01:51 PM, Bret wrote:
>> On Mon, 22 Nov 2010 14:30:08 -0700, AJL wrote:
>>
>>> Ashton > wrote:
>>>
>>>> If it exploded there was something wrong with the tire
>>>
>>> Maybe, but I think it's unlikely that I had 2 bad tires in a row. The
>>> first spare tire was brand new and came with my new 95 Taurus. The
>>> second was a used tire bought to replace it. Never had a third but by
>>> then I had started leaving the spare under-inflated.
>>>
>>>> or you are putting it in place with little or no air in it and then pumping it up
>>>> and forcing the sidewall against something sharp that cuts it.
>>>
>>> Nope.
>>>
>>>> The tires on the car get far hotter then the one sitting in the trunk
>>>
>>> Tires sitting on a parked car would be at or near the local
>>> air/surface temperature. Rolling tires would also be air cooled as
>>> well as road cooled. Neither gets as hot as the inside of a trunk (or
>>> passengers compartment) on a hot AZ summer day.
>>>
>>>> and they don't explode.
>>>
>>> Of course overheated tires explode, it's called a blowout. But in most
>>> cases rolling tire heat is caused by tire flexing due to
>>> under-inflation.
>>>
>>>> I"ve lived in Phx my whole life and have never
>>>> had a tire explode in the trunk, even really really old tires pumped
>>>> up to 40 psi cold.
>>>
>>> And we're supposed to pay attention to someone who lives in a hostile
>>> tire climate and touts using really really old over-inflated spare
>>> tires??
>>
>> You need to look for another reason.
>
>of course. cuts, bad valves, etc. when a healthy tire is inflated
>until it blows, it's a really serious BANG.
>
>http://www.youtube.com/watch?v=k3kq8iBkdoc

Air increases in volume about 1/273 per degree C. A temperature change
from -17.8 degrees C to 100 degrees C result in an increase in volume
of approximately from 1 to 1.2 and an increase in pressure of about
the same .

Cheers,

John B.

"Ashton Crusher" > wrote in message >
> I don't doubt his tires "blew up". What I doubt is that his claim
> that all the perfectly good tires in trunks in hot climates are in
> danger of "blowing up". Only a damaged or defective stationary tire
> is going to blow up because the pressure went from 32 (at 80 degrees)
> to 39 psi (at 150 degrees) (1 psi per 10 degree rise in temperature).

I agree, Ashton. It seems unlikely, but if he said that it did happen, I
do not impune his honesty.

Had a relative here who owned a service station a few years ago. He
was repairing a tire, and upon reassembly it blew off the rim, breaking
his legs. Lucky he wasnt killed. I have no idea what pressure he reached
(consider most service station compressor pressure capabilities) before
it blew,and if there were other reasons it happened.

I did a rough gas law calculation, and if the temperature went from 80F
to 180F, the pressure in my case would go from 60 psi to a little over
70psi. Not likely enough to blow up a healthy tire.