27 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHTires losing pressure
Reported or suspected cause
leaking valve stem valve
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
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Reported cause
Had a tire (not a Porsche tire) slowly losing air over time but not consistently sometimes the tire held air just fine and the problem proved to be a leaking valve stem valve.
Leading evidence: 'leaking valve stem valve' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'leaking valve stem valve' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check schrader incerts' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
I had to get one of my 3 piece rims resealed, rear tire was doing the same thing....
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Discussions that suspect a cause
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Suggestion
You'll have to check the wheel manufacturer's web site for any info on this process, or contact your local Porsche dealer for a lead to a wheel repair shop that can rebuild these wheels for you, or call around to wheel repair shops to find a shop that repairs these wheels.
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Suggestion
You'll have to check the wheel manufacturer's web site for any info on this process, or contact your local Porsche dealer for a lead to a wheel repair shop that can rebuild these wheels for you, or call around to wheel repair shops to find a shop that repairs these wheels.
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Suggestion
You'll have to check the wheel manufacturer's web site for any info on this process, or contact your local Porsche dealer for a lead to a wheel repair shop that can rebuild these wheels for you, or call around to wheel repair shops to find a shop that repairs these wheels.
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leaking valve stem valve
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause
Had a tire (not a Porsche tire) slowly losing air over time but not consistently sometimes the tire held air just fine and the problem proved to be a leaking valve stem valve.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
27 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Both rear tires will lose a few PSI in a few days. The fronts are fine and keep pressure. I run 44 psi in the rear and 36 psi in the front
About a 2 months ago, I noticed the left rear losing air and had a tire shop check the tire and could not find any leaks in the tire, no nails or cuts. Finally they found the bead leaking a little. They deflated the tire and put bead sealer on one side of the wheel where they found the leak. It seemed to be good for a couple of weeks, but now both lose pressure
It just seems weird that both rears will drop pressure the same amount and the fronts don't. All 4 are Pilot Sport A/S 3's and fairly new, maybe 5k miles
I have 275/30 ZR19 on the back and 225/35 ZXR19 on the front
The wheels are Zone Zone1 3 piece
Any thoughts?
1) Bad tire bead seat. Dismount tires, clean up the seating surfaces and remount.
2) Bad valve stems or valve stem seals. Check those areas with some soapy water and be patient.
3) Hairline fractures in the wheels. Can also find those with some soapy water.
4) Bad tires??
I have new Michelin Pilot Super Sports, and deducting pressure variations due to ambient temperature, they stay dead on for a long time. That's all I can think of so far.
Had a tire (not a Porsche tire) slowly losing air over time but not consistently sometimes the tire held air just fine and the problem proved to be a leaking valve stem valve.
To have both rear tires losing air pressure at the same time and the same rate...could be two bad valve stem valves I guess.
Are you sure your air gage is working properly?
If the leak is real then there's, well, a leak. Sometimes it take some patience at the tub of water to spot a leak.
Also, expand your view. Could be a cracked or porous wheel, make that wheels.
Be aware that when tires are mounted they should be lubed or treated with a special chemical -- TIP TOP Universal, order No. 593 0601 (3.5 kg bucket) or Contifix -- and then left to set for 24 hours.
Here's what the factory manual has to say: Use only TIP TOP Universal, order No. 593 0601 (3.5 kg bucket) or Contifix as the mounting paste!
If the tires are *not* properly treated and left to set a while they can spin on the wheel and this can result in a leak (or a wheel balance problem).
How old are these 3-piece wheels? those seals don't last forever. Note the high pressure in the rear wheels. 10 degree reduction of temperature equals 1 psi reduction. Try nitrogen instead of air, the extra cost is worth it to me.
I don't know exactly as we bought the Targa a few months ago and it had the wheels on it
Yes, temp does effect pressure, but the front should change as well and they don't
Yes, that's why I suspect it could be wheel related + the 44psi. If you can, wait & see how low the psi gets, I bet the rears won't go below front psi level.
if it sits a few days, high 20's to low 30's and the fronts don't drop
44 is the factory recommended pressure for the rears
I am going to go back to the tire shop and have them put bead sealer on both sided of each rear wheel
I did watch when they did the one 2 months ago and there were no bubbles. They pumped the tire to 80 PSI and still no bubbles.
The manager finally spotted the bead leaking with a spray bottle
I should probably mix up a soap solution and spray
if the 2 half's are leaking, can it be fixed?
I do not think bead sealer in this case is called for.
That the rears lose pressure but then stop I think has to point to the wheels leaking. Byprodriver I think hit this one out of the park.
The higher inflation pressure causes the wheels to leak, but after losing enough pressure the leakage stops.
I believe the wheels can be "rebuilt". You'll have to check the wheel manufacturer's web site for any info on this process, or contact your local Porsche dealer for a lead to a wheel repair shop that can rebuild these wheels for you, or call around to wheel repair shops to find a shop that repairs these wheels.
You can also plug in the name/make/model of the wheels and "repair" into a google search and see what hits you get.
Some 3-piece wheels use a huge 0-ring to seal the rims some use silicone sealant. Some recommend the bolts be replaced everytime. Hopefully you can find this information along with torque spec for the bolts. If not you need to find a shop that specializes in wheels like this. Assuming that the wheels are leaking that is. Nitrogen fill will buy you some time.
UPDATE----
I made a soap solution and sprayed it on the outside tire beads and low and behold, I saw some bubbles, so I think it is a bead seal problem.
I'm taking the car to the tire shop and going to have them bead seal both sides of the rears
The chrome often makes it difficult to seal the beads. Scratch up the bead area of the wheels & apply bead sealer. 44psi usually wears the tread in the middle unless you have a full load, 2+ people. I like 37psi.
Factory spec is 44 r and 36 f
At least that is what is on my gas door
Granted that is for factory tires and mine are 19's
So far, the tread-wear looks fine
Chrome? The local alloy wheel repair guy is a PCA member and multiple Porsche owner, he always says to NEVER get chrome wheels. Eventually the finish develops fine pits, allowing the tire to leak around the bead. Last time I was at his shop he had two sets of Mercedes chrome wheels being refinished, both for air leaks.
Not knocking your wheels, the point was that if the bead is actually chrome they are subject to pitting and leakage. I believe he fixes them by actually grinding the chrome off of the bead and sanding it out smooth.
My 996 Turbo has the same label on its gas door.
Those pressures are for a fully loaded car.
However, even at those pressures my experience is the tires appear to wear evenly. The real problem is the ride is rather harsh.
If you want you can drop the tire pressure by 2, 3, maybe even 4 psi and see how you like the ride, road feel, handling.
