I have the Potenza 245/40/19 summer tires on mine. What kind of pressures are folks using? Dealer has them pumped up to 40-42, handbooks says less.

I think mine are around 37-39

I run mine in that range. I always inflate them up towards the max. cold pressure.

I have the Potenza 245/40/19 summer tires on mine. What kind of pressures are folks using? Dealer has them pumped up to 40-42, handbooks says less.

Tag on the car shows 36 front and 39 rear. Almost impossible to hit those numbers I've found.

I run mine in that range. I always inflate them up towards the max. cold pressure.

That is incorrect. :nono:

Go by what the door jamb sticker says. What's on the tire is only to tell you what the max that tire can hold. The pressure on the door jamb is specific to each vehicle.

Note that the G8 uses staggered pressures (36 front, 39 rear) so if you go above that, you must maintain the stagger for optimum handling (ie. 37/40, 38/41, etc).

And FYI, the tag is on the driver door pillar above latch. Just noticed it myself today.

Tag on the car shows 36 front and 39 rear.

That is for max load. If you read the owner's manual, for lighter loads in the rear, the pressures are 36 at all for corners. Makes sense for a car that has almost 50/50 (unloaded).

Thanks for pointing that out. I'll go look at my tag tomorrow. So all G8's the tire pressures are the same?

I believe the 18's have a different pressure than the 19's. Read the owners manual. I can't believe nobody reads the manual to find this stuff out. 36psi for the 19's at all 4 corners unless you have high loads then it says to bump up the pressure in the rear. Mine were set high when I picked the car up. I haven't had a chance to drop the pressure when the tires are cold to get them to 36psi cold.

It can be 80* outside and as long as your car has been sitting for at least a few hours that's still a "cold" tire. :)

Agreed though, Look at the tag/plate on the doorjamb and that should list out the tire pressures for the car.

And as others said here, tire pressures are specific to the car, not the tire/wheel combo you have. What's listed on your doorjamb takes into account the weight of the vehicle and the suspension set-up. :wink2:

I know air temperature doesn't matter(much). What is it...like every 20 degrees is worth 3psi in pressure drop or gain? My problem is the car doesn't sit for a couple hours when I have time to check it. Always running somewhere or the wife just got home.

Yeah, I hear ya, I usually don't have the time to do it either. Either that, or I have the time and I'm to lazy to be arsed to go down and check it out.

I usually do try to check at least once a month though. Always have had a pressure gauge in my cars. Suppose I won't need it anymore when I get the G8 though eh?

Tire Pressure on your DIC (Speedo) and you don’t have time on the morning just look at it??

I've already looked at it. I'm saying it was set high when I picked it up(42 front 44 rear). I dropped the pressure to 36 cold today before we had to leave for the Inlaws. It's my wife's car so I've only gotten to drive it this weekend since we only picked it up on Monday.

I understand why there is a recommended pressure, I just don't follow it. Don't care about optimum handling etc. I just run them on the hard side for MPG and wear. When I need to I air down.

That is incorrect. :nono:

Go by what the door jamb sticker says. What's on the tire is only to tell you what the max that tire can hold. The pressure on the door jamb is specific to each vehicle.

Note that the G8 uses staggered pressures (36 front, 39 rear) so if you go above that, you must maintain the stagger for optimum handling (ie. 37/40, 38/41, etc).

I understand why there is a recommended pressure, I just don't follow it. Don't care about optimum handling etc. I just run them on the hard side for MPG and wear. When I need to I air down.Actually, running a pressure higher than recommended by the car maker will wear out the center of the tread faster than the sides as it will bulge in the center. Also you don't get a full contact patch with the road and lose out on grip.

Conversely, under inflated will wear out the sides faster than the centers.

Max pressure on the tire is what the tire manufacturer's stated max pressure that tire will operate at without problem, car manufacturer's recommended pressure makes sure that there is max contact with the road and that wear will be even.

Agreed with the above.

Also, haven't you seen that mythbusters where increases tire pressure does nothing for MPGs?:slap:

I double checked mine yesterday. They are at 36 and 37

Max pressure on the tire is what the tire manufacturer's stated max pressure that tire will operate at without problem, car manufacturer's recommended pressure makes sure that there is max contact with the road and that wear will be even.

That's pretty close, but the max pressure on the tire simply indicates the maximum pressure the casing was designed to hold (and the corresponding load that pressure gives).

The car manufacturer's recommended pressure is usually the lowest pressure that allows the tires to safely carry the vehicle's weight plus occupants and give the smoothest ride. For performance vehicles, the pressure may given to optimize the car's handling (which I suspect is the case for the G8).

Agreed with the above.

Also, haven't you seen that mythbusters where increases tire pressure does nothing for MPGs?:slap:Consumer reports also did some testing in a controlled environment and found that it took a big pressure change (like 10 to 15 psi) before 1 MPG gain or loss was measured. This was at an open house at their HQ. They said that roof top carriers were really bad for MPG and were 3-5MPG just due to wind resistance. They also said that windows open vs AC on the highway was a wash in the discussion.

Ok, ok...everyone do what they want. I'll keep mine up near the max. since it works for me. I understand traction/ tire wear. I also know that I get a lot of miles with even wear on all my tires. That is good to know that 10psi can be 1mpg...

On a side note, just how accurate is the TPMS supposed to be? I can check that my pressures are all 36psi with a gage, but the system always shows the left front 2 psi low.

friggin dealer had mine at 53 when i took it home!!!! they are down at 37 now.Idiots!!!

On a side note, just how accurate is the TPMS supposed to be? I can check that my pressures are all 36psi with a gage, but the system always shows the left front 2 psi low.

Yea, the TPMS readings seem to be approximations. I set all my pressures to 36 with a digital pressure gage, and then checked the TPMS and it varied a few pounds from wheel to wheel. Went and checked again with the digital gage and they were all still spot on 36. Or I guess my gage is broken and only reads 36 ;)

Pressure sensors were right on with my tire gauge.

friggin dealer had mine at 53 when i took it home!!!! they are down at 37 now.Idiots!!!

Ha ha! mine were near that range too!

They do it for they load of 3 or 4 people.

All 4 read 38 this morning on the way to work.

I'm a tire pressure junky, I've gotta have my fix every week. :driving:

I'm always adjusting a pound or 2, and trying to feel the difference. The 18" are at 36/39 also.

And the DIC is a DIC, the pressures are always off 1 or 2 tires, which drives me nuts.

I ran 38 all around last week, and it quickens the steering a bit. I tried 34 all around and it felt sluggish.

Remember, each 10 degree temp change raises the air pressure 1 lb if you're running air in them.

I have Nitrogen in mine (dealer tried to make me pay $65, but that didn't fly) They use green stem caps so you know. And it definately doesn't flucuate like regular air does, my pressure has been consistent whether it was 75 or 108 degrees here in Phoenix.