Danny Richie

I have a set of Michelin Pilot Sports all around. They tend to hold air pressure real well and I can go for weeks without seeing any pressure loss at all if just driving around town.

However, as soon as I get out on the highway to go anywhere I start loosing air pressure in the left rear tire. I loose about 5 pounds per mile. The left front has done this too but not as much.

I have taken the wheel and tire off twice and taken it to Discount Tire to check for leaks. They are yet to be able to find any leak.

So I put the wheel and tire back on the car and all is fine until I hit the highway and bring it up to 70 miles an hour. Then it starts loosing pressure again.

What is up with these tires?

R50THC5

I never lost air in mine. No help I know but have no idea what it could be.

NevadaVette

Try some soapy water around the tire valve once the problem starts. Look for bubbles to see if it leaks. Sometimes the fastening nut for the TPM becomes loose. Be careful if you snug it up - the torque spec is very low - maybe about 70 inch pounds - I don't remember exactly - just don't get carried away.

shaimerej

Sounds like a problem that is aggravated by forces developed while driving. It will probably be very difficult to find the exact cause! Look for a crack in the wheel. Wiggle and pull on the valve stem some. You may never find the exact cause? Good luck.

Res1cue

Odds are it the rubber seal around the valve stem. I had the exact same problem of losing air while driving and it drove me nuts. The seals are only a few dollars but the downside is you have to break the bead to remove the tpms sensor to replace it. When replacing add a tiny drop of blue locktite to the thread and make sure the nuts are torqued properly. Too much torque and you can damage the seals again. I think it 62in lbs

AORoads

As said above, it could be the valve stem nut and you do need to be careful how tight or loose it is. It could also be other things like wheel/tire fitment, too. You don't state if these are new, original, reproduction wheels. In the past, some reproduction wheels have been less than completely round/flat which can cause a leak at the bead (where tire edge meets wheel). One way to find out is to have the wheel looked at and spun without the tire on it.

A good hard bump can also cause any wheel, new or old, to develop a slight deformation which might cause this. I'll assume that your tire shop has checked for this already.

The fact that it does it to both LF and LR tire makes me wonder tho: did you ever hit a hard bump/curb/road debris on the left side? If so, those are the wheels to have spun w/o tires on them.

If you find the issue, do come back and tell us what it was.

GentlemanVette

Some tire shops have a tire balance machine called "Road Force"(or something like that) it simulates a static load on the tire vs spinning a tire round (with no bulge). Usually bigger bucks compared to standard spin balance, but it may be able to reproduce the cause of the leak in a controlled environment. Safer, my Corvette brother. Also I would think the shop you purchased the tires from (if they have RF balancer or equivalent) would do it a no charge Or a greatly reduced rate. Like mentioned in earlier post, tpms valve is a good suspect. My shop adds a sealant to my beads after a thorough cleaning. Well good luck and share the knowledge.

SUB VETTE

Not a systemic problem with a Michelin. I have PS2ZP's on my car with absolutely no problem. It's got to be a problem with TPMS sensor seals or as mentioned above, a wheel defect. I'd get the sensor seals changed to eliminate that source and then go from there.

Boomer111

Have you compared your pressure with a hand held monitor vs the TPM on the disc.

Sorry just had to ask.

Ketchum

Tonylmiller

I bet it is the valve stem, assuming you have done a thorough inspection of the tire. If the same person installed all the valve stems, maybe they did not know the correct torque or something.

John Harry

Yep, 62 in lb is correct.

Gearhead Jim

I would be reluctant to use the Loctite, though I use it on many other things.

Loctite will act as a thread lubricant, so instead of 62 lb-in you might want to use maybe 55-60. Not a big deal in this application.

More importantly, the rubber seal seems to slowly compress over time, and I prefer to tighten it occasionally. That's not practical with the Loctite.

We've had two C6's with two sets of wheels each. Once per year, I re-torque the TPMS nuts to 62 and they almost always move a little, and usually about the same amount on each wheel. So I don't think the nuts are actually backing off.

Where's BEZ06 when we need him???

Danny Richie

You guys have been very helpful.

The problem is not solved you but I think I am on the right track.

I squirted some soapy water in the valve stem. No leaks. So I pull around on it and found it to have some wiggle room. I would imagine that as highway speeds increase so too might the vibration at the valve steam and cause some air to leak from around it.

The left front was very slightly loose compared to the back one.

Both on the right side were very solid and did not wiggle at all.

So I may need to tighten them up. I am guessing I can do that without taking the wheel off? And that would come to 5.16 foot pounds (not much). I do have a torque wrench. I wonder if I can adjust it to that small of a setting?

Thanks guys!

rhrjr64

on my 05 i found after breaking down wheel and tire that the clear coat was gone and some aluminum oxide..white powdery corroded surface caused bubbles at bead

spdkilz911

I had this same problem. Tire was losing air, not just at highway speeds. I tightened the stem a little and tried again. After a few hours the tire was down again. I used some soapy water and found that the leak was at the base of the valve stem. I stopped by Discount Tire and they replaced the rubber seal between the valve stem and the sensor. Problem solved

Cyberwar

As others have eluded to and mentioned, the TPMS stems are not tight enough. I had the tires swapped onto a new set of GM factory comp grey wheels on my 2012 GS and the drive home on surface streets was fine. Once I hit the freeway things changed quickly. After about 3-4 miles at 75 mph, two of the tires started losing pressure rapidly. I turned around and headed back to the tire shop.

They confirmed they weren't tightened enough after the wheel swap. Tightened them up and it's never been an issue since.

Good luck!

Brian2010

Are you checking the pressure with a gauge, or by tps. My tps goes no response on my right rear on long rides. Im gonna take it to the dealer.

NevadaVette

When testing for leaks, make sure that you also squirt AROUND the base of the valve stem where it intersects the wheel as opposed to IN the valve stem.

Bill Dearborn

Not only can the seals go bad but the sensor bodies can go bad as well. They corrode due to moisture inside the tire, moisture from the outside that gets into the recess below the nut or the valve insert itself stops sealing properly due to dirt in the valve. Be careful on tightening the nut. My daughter's Torrent came with pressure sensors and when she replace the tires she purchased new sensors. Within a day two of them had blown off the outside part of the stem and left her with two flat tires. The tire guy tightened them too much.

Bill