[fe7565]

Traditional tire (not run flat)

For over a year one of my tires leaks from 33psi down to 26 psi in about a week (TMPS). I had the tire taken off and checked by a shop, under water, visual, etc..they replaced the valve steam. Still leaks...

Some suggested that maybe the rim has damage and allows air to leak out when I hit a pothole. So before a recent 5--days trip I filled it up to 34psi and monitored it. The 34psi remained during most of the trip. It seems to be losing air while parked vs driving. Does not make sense...

Any ideas?

[thejeremyman9]

Are you accounting for temperature variations?

[fe7565]

Originally Posted by thejeremyman9

Are you accounting for temperature variations?

Yes, thank you. My other three tires vary in unison with each other, and only 1-2 psi. This one tire I have to always refill, the others I don't have to touch.

[Ennoch]

Sometimes wheels are just a bit porous. From new my CRV has always lost c6psi over a month on three of the wheels while the other two (inc the spare) never lose a drop. This has been since my dad bought it new in 2002, through many, many sets of tyres, valves and different fitters.

[fe7565]

Originally Posted by Ennoch

Sometimes wheels are just a bit porous. From new my CRV has always lost c6psi over a month on three of the wheels while the other two (inc the spare) never lose a drop. This has been since my dad bought it new in 2002, through many, many sets of tyres, valves and different fitters.

Thanks for the comment. I also suspect that its the ril itself and not the tire. What do you mean by "porous"? Deformed due to damage or there is some sort of a structural issue with how the actual tire is mounted on the rim?

One more thought just came to my mind: I had two exact same brand tires develop side bubbles due to consistent potholes in my area. Wondering, if this tire (although no side-bubble) is deformed and not sitting properly on the rim? When the car drives the centrifugal forces allowing the tire to seal to the rim, but when parked there may be a very small leak around the rim? As I mentioned before, while driving for most of the day for 12-14 hours did not seem to lose pressure even after the tire cooled back down.

[Ennoch]

If it's only done it with this one tyre then there is the distinct possibility that there's something with the tyre, even if it's not dramatic enough to show when dunked in water. My way of finding leaks is to get some liquid soap (one that makes a lot of bubbles, preferably) and mix it as a strong solution in a spray bottle and douse the rim and tyre with it. You'll usually see little bubbles forming but you do need to check closely as sometimes they can be pretty small.

Do you know if the wheels have ever had knock on wheel weights used? These can be a bugger for causing corrosion on the aluminium as they're made of steel and cause galvanic corrosion when they inevitably chip the paint off the aluminium. This then gives very small channels for the air to leak out of. Also, corrosion can exist on the rim bed where the tyre seats, which can in part be overcome by liberal use of a coarse scotch pad and then an equally liberal application of bead sealing compound (although to be fair, a thick application of tyre soap can also help, I find the black stuff best). Another one that can accrue over time is as the valve stem wobbles in the valve hole when it's driven it can generate corrosion as it rubs the paint off and then the aluminium is open to the salt from the roads over winters. BMW's generally use bolt in valves so this shouldn't be a problem but you could try nipping the valve stem nut up a bit to see if that helps (or if air is still seen to be leaking from around it) then you can get a shop to take the valve out and either replace with a new one if it's an issue (I know you said the core was replaced by I assume you mean only the little inner core rather than the whole valve) or just re-seal the existing one with some instant gasket.

With porosity this is a more difficult one to fix. There are some treatments that involve soaking the wheel in various solutions once the paint has been removed which has the effect of clogging up the pores in the aluminium (same thing that happens with porous heads, cast aluminium is a bugger). However, a decent powder coat can have similar effects for less cost, but also with less guarantee that it'll fix the problem. However, even if it doesn't, it should certainly reduce the severity of it quite significantly.

Try leak hunting yourself with the soap and I reckon you'll find something that's easily fixed, porous wheels don't tend to suddenly start losing air in large amounts, it either does it from new or builds gradually over time.

[freakystyly]

+1 Soap test, use some dish soap and a wet sponge.

I've had a winter tire this year that was leaking at multiple places around the bead. This caused a very slow leak that slowly got worse. It just needed to be reseated and now it holds fine.

[fe7565]

Thank you both! Great details and suggestions. I will try the soap test first and see where it takes me...

[fe7565]

Originally Posted by fe7565

Thank you both! Great details and suggestions. I will try the soap test first and see where it takes me...

Gentleman, both of you were correct about starting with soap bubbles. There was a barely noticeable leak in the middle of the threads.

When I took it to the shop and removed the tire there was a thick nail about 3 inches long standing straight like a pecker

What must've happened when I took it to the shop the first time about a year ago was that they put it under water and the leak was so small they didn't notice it so they assumed the valve stem was leaking. So when they replaced the valve stem, they only focused on that area and never bothered to look at the inside walls.

Mystery solved. Thank you again!

[Ceane89]

Had a similar issue for over a year! Some times the tyre was deflating some others not. The paint on the rim had cracked in a place where the tyre was touching and it was leaking from there. Not sure why some times yes some others not, I guess it had to do with the position the leak was when parked

[montr]

As other posted said, spray a soap solution.
I had the same problem with one tire on my 2018 F36. I took the car to Costco (where I bought my Michelin tires) and they did not find any issues, they jus put more air in the tire.
Got the car home and removed the problematic wheel from the car. I sprayed a water and dish solution all around each side of the tire, one side at a time. After few minutes I found a small barely visible crack in the wheel. The next day, took the wheel to a nearby wheel repair shop. I think it costed me about $100 for a weld repair.

[Ceane89]

Originally Posted by montr

As other posted said, spray a soap solution.
I had the same problem with one tire on my 2018 F36. I took the car to Costco (where I bought my Michelin tires) and they did not find any issues, they jus put more air in the tire.
Got the car home and removed the problematic wheel from the car. I sprayed a water and dish solution all around each side of the tire, one side at a time. After few minutes I found a small barely visible crack in the wheel. The next day, took the wheel to a nearby wheel repair shop. I think it costed me about $100 for a weld repair.

Mine was less costly. They just wirebrushed the part the paint had peeled and all sorted. It was not a flawless rim anyway and was on the inside..