Tire loses pressure too much when temprature below 40 Fahrenheit

I have my tires replaced at Costo 3 year ago and after that my front driver side tire lose about 20 PSI every night as long as night tempresure below 40 Fahrenheit. 2 year ago, I went Costo and replaced that tire with another brand new one, the same thing. I went different Costco Tire Center and checked, they found nothing on either tire or the wheel. One year ago, when I do a service at Mercedez dealer, they found that Costco Tire Center switched my driver side front and back wheels which are different size. The dealer corrected that, but the loss presure continue happens on the dirver front side tire. I’ve own this car for years before I replaced its tires 3 years ago, and there was no any pressure lose even 1 psi (doen’t matter how low the tempresure even during winter), and all 4 tires maitained their tire pressure. I’ve went different Mercedez dealers and Costco Tire Centers, they all have no idea. Any thoughts here would greatly appreciated.

How are you measuring the pressure ?
With a gauge or the TPMS of the car ?

both a gauge and the TPMS of the car (on the dashboard)

@CapriRacer I think this is in your area .

I suspect the rim has a crack and that crack opens up when it’s cold.
This won’t be easy:
Put the wheel in a walk in or large refrigerator cool it down near 32F.
Spray soapy water all over it; look fo bubbles.
You could also wait for cold weather and do the soapy water spray.

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no, as I said, before i replace the new set of tires, my car can maitain the tire pressure perfectly. I only put a couple of psi once when winter begin each year, and release a few psi when summer begin once each year

As I said, both dealers and Costo Tire Centers, found nothing on the wheels

And it’s interesting enough, the passenger side 2 tires maitain the tire pressure perfectly as before the tire replacement. Is it possible that the tire pressure sensors/controllers were damaged on the driver side during the tire replacement, especially they switched the wheels of the front and back mistakenly on the driver side when replaced the tires?

I must insist there’s something on that wheel, losing air.
Cracks can be impossible to spot with the naked eye.
Did they test for air loss while it’s cold?
I’m pretty sure aluminum alloy can’t be magnafluxed.


I’ve had leaks develop in the rim from rust and of course the lower the pressure, the more movement and the more leaks. I had one tire that the only way I could find a leak was to submerge it in water and then wait for a bubble every minute or two, Yeah it was around the valve stem. So no magic involved. Tires leak, rims leak, valves leak, valve cores leak, and pressure goes down with the temperature. Don’t know what else to say.


Yeah, they tested air loss while it’s cold. But they couldn’t found any thing. I wonder if the car has something not related to wheel/tire/valve that would result the pressure loss. Before they replaced the tires, my care never lose air even during winter below frozen. When they replace tires, they couldn’t damage the alloy wheel I presume.

My wheel has no rust. Both Costco and the dealers put the whole wheel with tire in soap water and never found a bubble. The 2nd time when Costco replaced the tire, they also replaced the valve. After visited 4 different Costco Tire Center technicians and 2 Mercedes dealer technicians, and no clue. I was hoping Tom and Ray could shed a light on that.

The expansion rate of aluminum is 2.4 times that of steel. That means that the alloy wheel will shrink a lot more than the steel in the tire bead.

I suspect there is a flaw in the wheel that is being revealed when the temperature goes down - and that the only way to find that flaw is to take the tire off the wheel.

To help locate that flaw, it would be nice to get an approximate location by finding the leak - but since it is temperature related, it is going to be difficult. Even moving the assembly into a warm room might be enough heat to seal the thing back up. Besides, most shops are geared up to find large leaks, and .we are probably talking about a small leak, so that requires patience - something not in abundance at a tire shop.

My suggestion would be to have the shop debead the tire and apply some bead sealant. This might require a couple of tries to get it to work.


Actually, one Costco Tire technician did that (applied bead sealant), but not solve the issue.

Any one has similiar issue caused by mounted the rear wheel to the front and the front wheel to the rear. The 2 wheels are different in size a little bit, so the tires. Front tire is 225/45RF17 91W, rear tire is 245/40RF17 91W

Had an s10 with iroc rims that were marked front and rear, did not see the markings…I hand mounted 4 new tires and got driver side front and rear in wring places, the front wheel on the rear physically made contact with the hub when mounted, these where mag style alloy rims, as I tried to drive I heard scraping…stopped reexamined my work and found the markings…switched rims to correct positions…next morning front driver side flat, outside temp was about 42f, aired tire up drive to work 45min away, came out end of day around 60f and tire was still inflated…drove home night came 40ish lows next morning tire flat…took off, put in dunk tank, no air leaks, mystery begins…after 3 weeks of playing air tire up, buddy of mine suggested putting soap in water in dunk tank, completely submerged wheel/tire in now soapy water and left with an extra 10psi over in tire while we worked on stuff and had couple cold beverages, came back 2hrs later and a patch of very fine bubbles in tank corner, added a bag of ice to tank, bubbles got faster once we got temp down…broke tire down, using purple mechanics machine dye for finding cracks, found hairline crack around around mag spoke from where I mounted and made contact…s

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