Fixing a slow air leak in rear tire.
 

I have a very slow air leak in one of my rear tires. I lose about 10 psi per week. Since I don't drive the car everyday, I just add air everytime I go out but it's definitely annoying. I have attempted to have the tire fixed twice. Once at a Porsche dealer and another time at an independent performance shop. Neither of them could find the problem (but they both like to charge me $40 for their effort). The tire is the original Pirelli P-Zero Asymmetrico 295-18" mounted on an OEM hollow spoke turbo twist rim. The tire has about 12,000 miles on it and I keep it inflated to 44 psi. There is no visible damage to the rim or tire (other than treadwear). I'm thinking about trying tire puncture sealant that's sprayed into the tire through the valve but wanted to see if anyone had any experience with that. Any other advice to address this annoying tire leak is appreciated.

Tire sealants are meant as temporary measures, not long term solutions.

When the dealer and tire shop took a look at the tire, did they submerge the tire to find the leak or check the valve stem?

if it is loosing that much air it is a substantial leak...like Bob said I have seen many tire installers that don't even tighten the value stems let alone dunk the tire to make sure there are no leaks...there could also be a problem with the tire bead itself...the tire/wheel needs to be dunked in a tank to find the leak...one that bad will show up easily

I had the same problem with one of my tires about a year back. Although the tire shop couldn't find air leak on the valve stem, I purchased new stems from HRE and asked the shop to replace it and problem fixed.

The dealer claimed to have submerged the tire and could not detect a leak but changed the pin in the valve stem. The independent shop claimed to have tested the tire overnight by overinflating it to 60 psi and checking for leaks but could not detect a leak.

the problem with inflating it to 60 pds and then dunking the tire is that if the problem is a bead seal then the extra tire pressure could seal it better and when it is at normal pressure the bead leaks...take it to someone you can trust and have them remove the tire and check that the valve stem is tight enough to seal on the rim..they can also spin the rim and check it for trueness...then remount the tire and dunk again...sometimes just removing the tire and remounting will form a better bead seal...there is also a bead sealer that they can apply that might help...good luck...

Hello Jakeskiny,

Give me a ring if you would like. I have a couple of guys that should be able to help you out in your area. Sounds like a couple of possible scenarios.

1. Something punctured the tire and broke the head off making it very difficult to see unless the tire has been removed. (you may want to ask them this)
2. Depending on the finish, you may have some corrosion around the bead seat of the rim. This usually would occur with a chrome finish, but can also happen if you live in a region with lots of salt or moisture.
3. Defective Valve Stem.

Also, make sure you visually inspect the wheel to make sure there are no gouges near the bead seat area on the rim.

Talk to you soon.

Guy!

It's Justin! I came in with Bucky yesterday. Enjoy the new ride, looks great!

I had a similar leak on my car and tracked it down to the valve stem where it bolts to the barrel of the wheel. I don't know if the stock wheels have the valve stem bolted to the barrel, but that can be another place to look. The nut had backed out a few turns and once I tightened it up, no problems since!

12K miles...isn't it time to replace them anyway? :)

I had a similar problem; not on my Porsche. The local tire store said it was dirt that had gotten between the tire bead and the rim.

They took the tire off, cleaned the contact surfaces, reinstalled the tire, and it didn't leak anymore.

That is a great point. That scenario is usually very difficult to diagnose unless it's a large pebble.

This typically occurs if the shop doing the install has a dirty lube brush. (Dropping it on the ground etc)

If this does occur, make sure that the dirt/rock did not gouge the bead seat area or you may still end up with a leak.

In my case the installer told me that it was road dirt that had worked into the bead seat from outside the wheel.

It might have been that he used a dirty brush but the tire was OK for over a year after the tire was installed. He said he sees this situation frequently.

I live on a long dirt road.