Tire p Question

Hi,

This a funny one, I think:

Have a 2009 Buick with the automatic reading tire pressures.
Really neat; assuming it's accurate, you read the actual pressure in the
4 tires.

Let's ay I fill them all up to 33 psi.
Each tire reads then 33 on the car display.
Fine.

But after a few days, one of the tires, always the same one,
shows (on the car's readout) 29 psi.

The thing that confuses me is that it never goes lower.
Always drops about 3 or 4 psi after filling the tires up, in the course
of a few days, and stabilizes there.

I would think that if it was a slow leak, it would continually keep
losing p and go down more, and more.

But this isn't what happens.
Loses the 3 or 4 psi after a few days, and sits at that lower p.

Any idea what might be happening ?
Is it the tire, or...?

Thanks,
Bob

"Bob" > wrote in message
...
> Hi,
>
> This a funny one, I think:
>
> Have a 2009 Buick with the automatic reading tire pressures.
> Really neat; assuming it's accurate, you read the actual pressure in the 4
> tires.
>
> Let's ay I fill them all up to 33 psi.
> Each tire reads then 33 on the car display.
> Fine.
>
> But after a few days, one of the tires, always the same one,
> shows (on the car's readout) 29 psi.
>
> The thing that confuses me is that it never goes lower.
> Always drops about 3 or 4 psi after filling the tires up, in the course of
> a few days, and stabilizes there.
>
> I would think that if it was a slow leak, it would continually keep losing
> p and go down more, and more.
>
> But this isn't what happens.
> Loses the 3 or 4 psi after a few days, and sits at that lower p.
>
> Any idea what might be happening ?
> Is it the tire, or...?
>
> Thanks,
> Bob

Is the (automatic) 29 psi readout confirmed with an actual pressure gage
reading? Your comments do not make that clear. Have you also measured
(pressure gage) the other tires to verify the car readout? If the low (29)
pressure is confirmed via a gage then you've got a tire problem--if not,
then a pressure sensing (car) problem.
MLD

Have the tire checked for a slow leak.

"MLD" > wrote in message news:i27ne3
>>
> If the low (29)
> pressure is confirmed via a gage then you've got a tire problem--if not,
> then a pressure sensing (car) problem.
> MLD
>

It might not be a tire, but could also be the tire/wheel sealing surface,
a leak in the metal wheel itself, or a slightly leaking valve stem.

We just got back from a long road trip and picked up a small piece of
wire in the tire (from a truck tire belt decomposition in the desert). We
remember when we think the puncture occurred.....several days before
the tire leaked down enough to register. Even so, we found the wire
with soap solution.

Complete immersion in soapy water is also very sensitive.

"hls" > wrote in message
...
>
> "MLD" > wrote in message news:i27ne3
>>>
>> If the low (29) pressure is confirmed via a gage then you've got a tire
>> problem--if not, then a pressure sensing (car) problem.
>> MLD
>
> It might not be a tire, but could also be the tire/wheel sealing surface,
> a leak in the metal wheel itself, or a slightly leaking valve stem.
>
> We just got back from a long road trip and picked up a small piece of
> wire in the tire (from a truck tire belt decomposition in the desert). We
> remember when we think the puncture occurred.....several days before
> the tire leaked down enough to register. Even so, we found the wire
> with soap solution.
>
> Complete immersion in soapy water is also very sensitive.
>
Tire... as mentioned, infers that it also includes all sub-systems vs the
auto pressure sensing system. I thought that it was obvious....apparently
not.
MLD

"MLD" > wrote in message
>>
> Tire... as mentioned, infers that it also includes all sub-systems vs the
> auto pressure sensing system. I thought that it was obvious....apparently
> not.
> MLD

No, not at all. A lot of people take "tire" as "tire" . You are right that
they SHOULD consider tires and their sub systems, but that is not
always the case around here.

I have seen wheels fail, especially where the bead seals.
Occasionally I have seen wheels corrode from inside and give a slow
leak.
And many trust the valve stem a lot more than you should. Leaks
past the valve are common, but also common are cracks in the
stem, or leaks around the mounting hole.