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Discussion Starter #1
The tire pressure of the same tire is always going low during cold weather - and if I don't get to it soon enough it goes so flat it can't be refilled without going to a shop and resealing the bead.

Guys at the shop have checked the tire, no leaks, and don't see anything wrong with the wheel but obv something is wrong.

The scenario goes like this - after a cold night the low pressure indicator light is on in the morning and the pressure is low. I head to the station, refill it up and all is fine. If I get another cold night same thing happens.

I just came back from a trip, left the mdx at airport parking for 4 days, it was cold, got back and the tire was so flat I couldn't refill it, the bead was no longer on the wheel.
 

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Have them remove the tire. Get them to clean up and remove any dirt and corrosion off the rim. Reset the tire with new seals on TPMS or new valve stem.
 

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Make up a spray bottle of soapy water and spray it all over the tire, especially the bead area and the valve stem area. Chances are that you'll see bubbles where the leak is.

Occasionally a tire will leak only when it's in a certain position with the weight of the car on it. That might be why your tire shop couldn't find it.

Cleaning up the bead area, as suggested by boston above, is never a bad idea. In the old days, you'd also replace the valve stem, but I'm not sure what's involved now with a TPMS system.

It sounds like you're driving on the tire when it's very low. I'd strongly discourage that. You can damage the sidewall pretty quickly and make the tire unsafe to use.
 

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Discussion Starter #8
I'm confused. Earlier you said no leaks were found. Now you say the leak was found. Which is it?
Sorry, by no leaks I meant the tire didn't have any punctures. Yes, there is for sure a leak around the edge of the tire where it comes into contact with the wheel rim. But the guys at the shop say they don't know why, they don't see anything wrong with the rim of the tire. The tire was taken off, put on some machine, and no punctures were found. The wheel was inspected and they don't see anything wrong with it. But when the two are put together there is a bit of a leak around the area where the tire and wheel come into contact,
 

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Discussion Starter #10
Getting annoyed...

Got a new tire, wake up this morning and the tire is low again the same one - it was at 22. The other front tire did not have the indicator light on but it was 26. Both should have been 32. What is up?? The low last night was 25*F.

Other question - should I even be filling these up back to 32 psi in the morning? Someone mentioned that it happens to them, not on an MDX, and later in the day when it warms up the tire pressure is back up. 22 psi just seems way too low to drive with, even if psi will go up later in the day.

I understand that cold temps contracts air, thus lowering psi, but this issue caused a flat for me before but I have since got a new tire and here we go again. I would say there was an issue with the wheel but, like I said, the other tire was low as well. None of this was happening in the summer/fall...

Two main concerns:

1) I know it's normal, relatively, to have the indicator light come on in cold temps, but should it be as low as 22 psi?

2) will filling them back to 32 psi in the morning, then having warm temps later in the day expand the air and cause the psi to go too high?
 

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The Tire Rack says that pressure changes by 1 psi for every 10 degrees F change in temperature. In most places the difference between normal early-morning temperatures and normal mid-day temperatures is 20-30 degrees, so the pressure changes during the day due to swings in normal temperatures should only be around 2-3 psi, "measured cold" (i.e. when the car is in the shade and hasn't been driven in a few hours). If you do most of your driving during the day, set it at the normal temperature then, and don't worry if it's 2-3 psi low when you first set out in the morning. If you do most of your driving at night, set it at the normal temperature then, and don't worry if it's 2-3 psi high whenever you're driving around at mid-day. (Of course, any particular day can be 40-50 degrees above normal or below normal; don't set your tire pressure on those days.)

As you can see, a difference of 10 psi cannot be explained by the difference between normal morning temps and normal mid-day temps. Did you set the tires at 32 psi when they were hot (right after driving somewhere), or inside a warm garage? If so, that is a possible explanation for why your tires don't have enough air in them. You need to set the pressure when the tires are cold (the car has sat for several hours at the normal outside temperature, out of the sun. Otherwise, if you set it at 32 psi (measured cold) and then measured it at a temperature 20-30 degrees colder and it's down to 22 psi, then the tire is actually losing air (and won't go back up to 32 psi, measured cold).
 

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Discussion Starter #12
Did you set the tires at 32 psi when they were hot (right after driving somewhere), or inside a warm garage? If so, that is a possible explanation for why your tires don't have enough air in them. You need to set the pressure when the tires are cold (the car has sat for several hours at the normal outside temperature, out of the sun. Otherwise, if you set it at 32 psi (measured cold) and then measured it at a temperature 20-30 degrees colder and it's down to 22 psi, then the tire is actually losing air (and won't go back up to 32 psi, measured cold).
The tire pressure for the new tire was set by the garage in the afternoon - so the tire was cold (as in it was not recently driven) and the air temp was warm. It was fine for a few days, the temp then dropped considerably last night)

To get this right - you are saying the pressure should be set when the tires have not been driven on for some time (thus they are cold) AND when the air temperature outside is not very low? So, to sum it up, set the pressure when the tires are cold and the outside temp is warm?

I'll give it a try but all this seems a bit much - I drove and old '87 Nissan 15 yrs ago up in Canada and never had this problem.
 

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To get this right - you are saying the pressure should be set when the tires have not been driven on for some time (thus they are cold) AND when the air temperature outside is not very low? So, to sum it up, set the pressure when the tires are cold and the outside temp is warm?
Not exactly. I'm saying, set the pressure when the tires are cold (i.e. haven't been driven in the previous hour or two) and when the temperature where the car is, is what is typical for when you're driving the car. For example, if you normally drive during the daytime and it's 50 degrees F during the daytime, set the tire pressure when it's around 50 degrees out. Hope that makes sense.

I'll give it a try but all this seems a bit much - I drove and old '87 Nissan 15 yrs ago up in Canada and never had this problem.
Actually, that's true for any car, and was just as true 20 or 40 years ago as it is today. The only difference is that today's TPMS will tell you when your pressure is abnormally low. But the variations due to changes in temperature shouldn't be enough to set off the TPMS warnings.
 

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Discussion Starter #14
Actually, that's true for any car, and was just as true 20 or 40 years ago as it is today. The only difference is that today's TPMS will tell you when your pressure is abnormally low. But the variations due to changes in temperature shouldn't be enough to set off the TPMS warnings.
I get that it's true for any car - all tires have pressure and that pressure is affected by the air temperature. What I am saying is that in other cars I was in areas were the temperature differed between hot and cold but my tire pressure was never an issue, at least not to this degree. That old car I had never dropped PSI by 10 or 15 over one night.
 

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I get that it's true for any car - all tires have pressure and that pressure is affected by the air temperature. What I am saying is that in other cars I was in areas were the temperature differed between hot and cold but my tire pressure was never an issue, at least not to this degree. That old car I had never dropped PSI by 10 or 15 over one night.
Sounds like you didn't read my post, so I will emphasize my point by stating it again: The difference in overnight temperature will only cause a change of 2-3 psi pressure. If your pressure, measured cold, is dropping 10 psi overnight, your tire is leaking.

This is just as true of a car from 20-30 years ago as it is of a new MDX. The laws of physics haven't changed during that time, and don't affect one car any differently from another. PV=nRT is the law in question, and an outside temperature difference of 20-30 degrees F changes the pressure by less than 10 percent - any car, any tire.
 

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Discussion Starter #16
Sounds like you didn't read my post, so I will emphasize my point by stating it again: The difference in overnight temperature will only cause a change of 2-3 psi pressure. If your pressure, measured cold, is dropping 10 psi overnight, your tire is leaking.

This is just as true of a car from 20-30 years ago as it is of a new MDX. The laws of physics haven't changed during that time, and don't affect one car any differently from another. PV=nRT is the law in question, and an outside temperature difference of 20-30 degrees F changes the pressure by less than 10 percent - any car, any tire.
ok, calm down nsxtasy, no need to yell. If my reply offended you it was not intentional and as adults here I think we can all assume that we mean no offense to each other.

In general, all I am saying is that I've had other cars in the past, my friends have cars, and they are not getting any significant drops in psi due to the temp changes. Why am I losing over 10 psi in one night in a brand new tire when no one else is? This is not normal. I know this is not normal. I just can't figure out the reason.
 

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Why am I losing over 10 psi in one night in a brand new tire when no one else is? This is not normal. I know this is not normal. I just can't figure out the reason.
You have a leak. Find the leak. Find the root cause.

Follow the basic troubleshooting process.
 

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Definitely sounds like you have a wheel problem. Check for any hairline cracks. On my car (wife drives the X) I am losing about 10psi over 2-3 days and now it's getting worse. I have a hairline crack in the wheel, which is the source of the leak. The crack is on the inner part of the wheel so you wouldn't notice it unless you remove the wheel from the car. (and before anyone freaks out, I am in the process of dealing with the bum wheel)
 

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Discussion Starter #20
Up to this point I have been troubleshooting:
1. checked for punctures - none found
2. check the bead - leak found. Put the tire back on with an updated seal/bead
3. leak keeps happening at the bead but they can't figure out why, they say the wheel looks fine
4. get a new tire because the old one was damaged after riding the flat
5. new tire, old leaks

I agree that at this point it must be the wheel - if a new tire is leaking I don't see any other reason. I'll chk, have no idea how much a wheel costs...
 
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