Tire pressure changes for no reason

[rcs]

Good morning everyone. I have had new tires Michelin Defender LTX M/S for 1 1/2 years on my 2015 Honda Pilot. I always inspect my tires before I leave in the morning and at my destination. I always check my tire pressure before I leave also. I know I am OCD. Last week I took it to the dealership, because for no reason, not cold weather related I have been losing .5 to 1 lb of pressure daily. I have a Jaco digital and analog pressure gauges and they are always on point. The dealership checked the tires right in front of me and the reason for the pressure loss was the fill valves were corroded. I saw the bubbles myself when they sprayed them. So they put new ones in all 4 tires.
It stands to reason also that the batteries in these only last about 7 years, so I was due for them. I did see the corrosion on the old fill valves.

Now here is my question. I did not drive my car yesterday. I just checked the tire pressure to see if it held steady overnight from Friday. It is down 1 lb in ALL 4 tires! Can anyone help me with this, and explain why this might have happened? My car is in my garage, and the temperature is steady. I do not think this is right for it to lose pressure like this. Perhaps the new fill valves are bad also? The tech at the dealership who is awesome also said he balanced the tires because they were slightly off. I am so frustrated with this, I just want to get new tires, even though the tread on these is good! Could it be something with the rims or the tires also all of this time? I don't know. Hopefully, someone can help this lady in distress! Thanks for your time and responses.

 

[gman2304]

I know I am OCD.

Recognizing this at least means that you’re on the road to recovery!

 

[Mechanician]

Try spraying the valves with a little soapy water again. Also check the beads the same way.

 

[rcs]

Try spraying the valves with a little soapy water again. Also check the beads the same way.

OK,...tell me where the beads are? I am not that proficient in car lingo. And can this be fixed?

 

[rcs]

Recognizing this at least means that you’re on the road to recovery!

I like being OCD, keeps me on my toes, and is good for my career

 

[Boomer]

At the dealer, perhaps the tires were warm when he tested the pressure and set it. You drove home, tires were still warm but it sat overnight in the garage and the temperature of the tire lowered. Thus, pressure lowered. Drive a few days and keep checking. An every morning test BEFORE DRIVING will give you the best comparison, IMHO.

 

[wpod]

There is always a reason.

 

[eljefino]

I always lose a little air pressure after I do a bulk fill of my tires with shop air. It stabilizes after a day. I blame the shop air being warmer than ambient.

If I were you I'd try taking air samples every other day, then twice a week, then weekly. Not just as therapy but because you let a little out every time you sample, and you're putting wear and tear on the valve cores. It will also mathematically average daily changes in pressure related to temperature, which you are getting, even though you think you aren't.

 

[spasm3]

I like being OCD, keeps me on my toes, and is good for my career

Just realize that tire pressure is going to vary with temperature. I set mine after an overnight sit, 1-2 pounds over, and check monthly.

No need to check daily, but if it makes you feel better sure. But your tire pressure is going to vary everyday.

 

[goingplacesanddoingstuff]

It doesn’t take a large temperature drop to cause a 1 psi drop. I would attribute it to temperature, atmospheric pressure changes, and measurement error. Don’t worry about it until proven otherwise.

Tire pressure will always vary slightly every day.

 

[rcs]

The new fill valves were put in on Tuesday the 13th. He put in 35 PSI which is what the tire and car suggests. Wednesday, Thursday and Friday it was pretty steady. I did not drive yesterday, Saturday. This morning is when it went down to 34, in all 4 of them. I just put it
up to 36, because I like a cushion. I will see if it holds Monday morning. Thanks for all of your advice and input, it truly is appreciated.

 

[himemsys]

If you're consistently losing pressure, such that after a week they are all down 5-7 lbs, then there's a problem. But 1 lb can happen by how you measure the pressure, the temperature, the humidity, etc. So many variables. Sometimes I try checking the air 3 times in a row an get 3 slightly different readings. Don't sweat the small stuff.

 

[Propflux01]

1lb change for every 10*F is about the norm.

 

[rcs]

If you're consistently losing pressure, such that after a week they are all down 5-7 lbs, then there's a problem. But 1 lb can happen by how you measure the pressure, the temperature, the humidity, etc. So many variables. Sometimes I try checking the air 3 times in a row an get 3 slightly different readings. Don't sweat the small stuff.

It is humid here today in Michigan, temp is 77 degress. Tomorrow it is going to be 73. The night temps are supposed to be even lower, in the low 50's. I get it with the temperature change the pressure in the tire changes as well. I just thought with the constant temp in my garage, I would not have this issue. It just bums me out!
I will see how it goes this week. I am still going to call the dealership and ask them to check the fill valves again and the bead around the tires. Thanks again!

 

[rcs]

1lb change for every 10*F is about the norm.

Thanks for the info. Yes, it makes sense. Yesterday it was 78, last night 65 degrees so there it is, I guess. Even though I would think my garage kept the temp consistent. Thanks!

 

[John105]

I’m gonna say for all 4 to be the same, the ambient temp dropped 10F and 1 psi.

My friend Rey checks his tire pressure only upon replacement. We had an argument about it. Imagine how much more carefree he is, than we at Bitog

 

[John105]

Thanks for the info. Yes, it makes sense. Yesterday it was 78, last night 65 degrees so there it is, I guess. Even though I would think my garage kept the temp consistent. Thanks!

Yeah and when we first got costco tires which are nitrogen filled, I expected the tire pressure to change far less than 1 psi per 10F, but no. Still the same rate. What is also annoying on GM is when the car has 1 thats different. Say 37/37/37/35. Even my wife will say is that ok? I say yes. I’d say a week later 37/37/37/28, now something is wrong such as a leak. There is always 1 or 2 tpms that fluctuates….makes me wonder if too much info makes us worry unnecessarily….

 

[Mechanician]

makes me wonder if too much info makes us worry unnecessarily….

"A man with one watch always knows the time, a man with two is never sure."

 

[Mechanician]

OK,...tell me where the beads are? I am not that proficient in car lingo. And can this be fixed?

The beads are where the tire meets the rim, the seal area there can become corroded and leak.

 

[Kira]

A note on checking for leaks: With the tire off the vehicle and flat on the ground, you dribble soapy water where the tire meets the wheel -the bead seal. The amount of water isn't important as excess water will simply run off. The soapy water remaining will reveal bubbles. Wear your good glasses as the bubbles can be very small.

As said above: Alloy wheels corroding (oxidizing) at the bead seats is a known thing. The resulting roughness, while minor, can allow air to escape.
However, that you're seeing matching pressure differences on all 4 wheels would tell me you don't have that problem.

As others have said, temperature variations cause inconsistent pressure readings.
How 'precisely' you press on the gauge effects readings. Not only are you releasing air (not the largest source of error), but the full psi might not be hitting your gauge's guts if you hear the characteristic hissing. It's best to be familiar with one's gauge such that you can jab it on the valve quickly and squarely....not necessarily forcefully.

My wife and her sisters are taking a 1,000 mile trip come Thursday. All 4 of her tires (brand name withheld because it's immaterial) had 34 psi. It had easily been 2 months since I checked them last. She doesn't drive much, and the tires have always held air well.
I cranked them up to 38 psi (recommended 34...+ the time honored 10% for sustained highway driving = 37.4 thus 38 psi) two days ago.
I just checked them -as this thread inspired me- and they match at 38....good to go.

Aside from this particular exercise, keep in mind that the minimal/acceptable/unavoidable tire leakage is increased during the "Autumn + Spring" months. It's the temperature fluctuations through these days which increase leakage.

NOTE: I knew her rear tires were more worn...but now I see they're more worn that I remember. Time to tire shop!