cl0ud8888

dropped my tire psi to 31-32 all around on stock 18s becuase i felt like the ride was toooo harsh with 35-36.....but even with 31 with some people in the car i feel all bouncy and jumpy ...whats the best solution? lol and dont tell me to buy a lexus

Mr Marco

Yep, you bought the wrong car. Trade down for 17's, or Get a Lex...
And I must also ask, where did you go on your test drive?

friesm2000

iTrader: (4)

the tires might actually be TOO SOFT now, allowing them to be bouncy and such (maybe try 34 psi instead) (and with people in the car [added weight] it is even more important to run enough pressure in the tires)
does the car feel fine with JUST YOU in the car?

or get some 17's instead, or a Lexus as said...

Stew4HD

change the springs to softer ones too... get baloon tires ... or get a lexus.

31-32 psi will wear your tires out faster on the other edges.

I haven't heard of this complaint before.

Bearcat94

Have you considered a Lexus or smaller wheels or softer springs?



30 psi is too low for that profile and vehicle weight.

Oswald Vater

I think the factory specs are 32 all around? That's what I run mine at and am happy with both the ride and the wear factor. It may be different for the SH - mine's a base/tech.

Bearcat94

Didn't you want to suggest the possiblity of a LEXUS?!?!?!

prepreludesh

Hey, slightly off topic here, but has anyone noticed that the actual air pressure (measured with an air pressure gauge) is always higher than what the TPMS readout shows? I make sure my tires are at 32PSI, then when I turn the car on, the display shows me that the fronts are at 30 and the rears are at 29. What's up with that?

justnspace

iTrader: (1)

Here's a suggestion: trade for a Lexus!

Takehold66

Mine are always exactly the same as the gauge. I set them to 34 then turn on the car and the TPMS says 34. All gauges are calibrated a little differently I guess. Mine just happens to be the same as the TPMS. I use this one. http://www.amazon.com/Accutire-Stand...216914&sr=1-14

friesm2000

iTrader: (4)

there is always a slight varience possible, especially with a mechanical gauge, the biggest thing is having it be consistent each time, so that you can compensate for it




btw have you been to the regional sections; i see colorado springs under your screen name

crxb

Mine are set to the factory spec of 37 F and 32 R

I have to remind the dealer when I bring it in - as they will (and have - I believe every time) set the tires to 32 F and 32 R

((the HPT option (the 19s) )

the tires have worn just fine - even the rears at 32

My 3G (2004) was bad about the rears wearing a on the inside - if the car was loaded up - (4 -5 kids/adults and gear, car trip)

--last my TPM and my hand held TP gauge match

Bearcat94

My 3G is right on with my guage EXCEPT for 1 tire which is within 1 psi of my guage (I think it's off by about 1/2 psi, because sometimes it's the same and sometimes 1 psi lower).

prepreludesh

I swear I'm not using a cheap gauge guys! It's a "Slime" one that's a few years old, but it's got like an inch and a half sized needle gauge on it, all brass construction and a nice solid air release button on the side. But I guess the mechanical gauge doesn't matter much because the TPMS will go off based only on what the sensors are saying, not my gauge. So it looks like I'll have to stick with what the sensors are saying...

Oswald Vater

The thought crossed my mind but was quickly squelched

TinyRK

Isn't the readout also temperture-depending?
When it is warm, the pressure in the tire will be higher than when it's cold.

When it's cold here (Wisconsin) my pressure is around 30psi. Now it's up to 32.

And yes,
get 17' or trade for a Lexus

Mr Marco

I agree with the Badger^!

TinyRK

So, today I checked: outside temp ~57F.
All 4 tires show 36psi.

Way different than the 30psi the display showed at -20F outside temp.

friesm2000

iTrader: (4)

seems about right for the different temps

crxb

Temperature and pressure are directly proportional to each other. This means that as the temperature decreases, the pressure also decreases, and as the temperature increases, the pressure increases. One way to think of this is if you increase the speed of the molecules –by increasing their temperature- the force of the molecules hitting their container increases and this increases the pressure. This relationship is called Gay-Lussac’s Law and makes up part of the ideal gas law.
Theory
When the speed of a gas’s molecules increases, the gas molecules hit their container more often. The more frequently the gas impacts the container walls, the higher the pressure. So, as temperature increases, the pressure also increases. If the gas cools, the impacts are less frequent and the pressure decreases.
This relationship can be described using mathematics as well. Mathematically, Gay-Lussac’s Law states that
TP = k

TinyRK

crxb, nice explanation, but I know (I am an Electrical Engineer ) and my questions were rather rethorical since bobody else brought that up. And the OP might not know and will be rolling on the rims next winter, depending on where he lives.

Down South you won't have such temperture differences, I guess, but Wisconsin Winters are brutal, that's why we drink a ot.

Up here 60F Delta-T results in ~6psi Delta-P. So watch out!


To be honest, this is my 1st car with TPM, so I was rather impressed how reactive this system is.

vinnier6

iTrader: (1)

adjust your tire pressure with your seasonal temps....when its colder out, when your tires are reading low, add air to bring up the pressure...when it gets warmer out, adjust accordingly....that way you always have the correct tire pressure...

friesm2000

iTrader: (4)

for all engineers:
f@cking engineers, i want to see you guys actually work on a car, and see some of the bullshit that you guys engineer into cars, and how you many other parts you have to remove in order to get to a simple part causing issues, because there is just not enough room to access it otherwise

crxb

here in the dfw area this winter we had a few extreme cold days (extreme at least for N TX with around a 100 hrs below freezing (that was the day we had rolling black outs through out much of the state) - one day the low was somewhere in the teens and even here I saw your ~6psi Delta-P - that from a correct tire pressure set probably around 70'F

Oh and the "explanation" was a cut n paste

Now for the Engineers - If in ""theory"" you had less water vapor in a tire filled with Nitrogen - would you see less pressure fluctuation w/ temp swings than the same tire filled with "air"

I mentioned water vapor" as nitrogen is a gas that will react to Temp changes like any other gas

friesm2000

iTrader: (4)

i will say though that that water vapor expands more readily then straight nitrogen

SO you actually need to run higher pressures then you would with air, to compensate for the lack of expansion originally designed into the tire pressure placecard



btw, GM actually recommends against running nitrogen, because once you contaminate the tire with regular air, basically all the "benefits" are null, and the issue is also getting pure nitrogen, nowhere close to having the same availability as air either (not as bad today, compared to even just a couple of years ago though)

but here is another thing also though, tires normally don't rot from the inside out, normally they just get worn out, so any benefits there are also kinda pointless in a way

Stew4HD

Umm.. guess what.. not all f@cking engineers have anything to do with the automotive business. .. that is like saying all Beekeepers need to stop gutting fish!

Your post does crack me up.. they do enough to put 20 pounds of parts in a small container but you think each part should be readily accessible?

Even in the good ole days, to cahnge the water pump on a '72 Cougar, I had to remove the radiator and shroud, fan, pulleys, alternator, A/C compressor, piower steering pump.. just to get to the water pump... And those cars actually had space to work on them!
Cars are now smaller and more compact yet have MORE shit under the hood than that '72 Cougar did.....

Kingmeow

Hey, you want easily accessable parts??? Get a bicycle.....

SSGHutch

off topic a bit, but what about nitrogen filled tires? Anyone have experience with this? Is it worth it? With the amount of traveling I do my psi varies wildly and I'm tired of constantly having to adjust it.

Loli

I am surprised that no one has mentioned getting different tires if you don't like the ride you get from the tires that are on the car.
I think the ride can be improved and am thinking about getting different tires when my OEM tires ware out. I am looking at the Bridgestone Potenza RE960AS Pole Position. I have read a lot of good reviews about them. I understand that they are not as good in snow but then I will buy snow tires and rims.

I can't wait for the OEM tires to ware out.

MGG

Tebaz06TL

in the winter mine would say low air pressure, i would just ignore it till my tires heat up, they are nitrogen filled and i'm not going to the dealer to get that adjusted everytime i get in the car. now that the weather has changed i'm sure while I'm set at my 32psi it will increase a few degrees the difference in ride comfort is really ignorable. unless you plan and transporting anti matter in canisters.

bliss!

Trying to avoid making a new thread since there's one talking about tire pressure already on the top of the forum.

I just had my TL with Tech package, with the stock 17" wheels and tires, for a week now. The MID says all tires are around 270 kPa, which is about 39 psi according to online calculators. The recommended pressure of 32 psi is around 220 kPa. That seems somewhat excessive.

I've been driving about 150 km or 93 miles in 10-15 degrees C or 50 F weather. The ride is fairly harsh, feels like I'm in a 1990s SUV.

I sort of think the pressure has been dropping slowly over the week. Should I release some air by hand until I'm around 32 psi or 220 kPa? Or will they drop by themselves slowly?

The readings are done when the car has been sitting overnight and increases slightly after driving.

Takehold66

^ drop them to 32 by hand when they are cold. They will increase to 33 or 34 as you drive which is normal. The next morning they will be back to 32 as long as the outside temp is about the same as when you adjusted them.

bliss!

Awesome, so just release the air by hand the old fashioned way, measure and fill it back as needed?

I wasn't sure if I could do that on this car, with all that technology. My previous car was made in the 90s. This is quite an upgrade.

Will do this in the morning tomorrow. Hope the ride won't be as harsh as it is now. On the upside, I've been getting good mileage numbers for a brand new car, 10L/100km or about 23.5 MPG in the city and with a little bit of heat on. Don't know if the hard tires are contributing or not.

Bearcat94

Right, the "old fashioned way".

I make adjustments seasonally as well. Occasionally "in season", but not too often. Once you get 'em set for prevailing temps, they'll stay pretty close for weeks at a time. Sping and fall are hardest because the temps are moving all over the place.


And, FWIW (which probably isn't much), when they dsay measure and adjust the pressure when cold they don't mean wait for a cold day. They mean when they are at ambient temp. Usually before you've driven the car for the first time that day. Even a short 1-mile drive can heat the tires up and give you a "warm" pressure reading.

bliss!

Thanks.

No issue for the "cold" tires. There is a gas station one and a half block or 450 m/0.3 mi away with a free compressor. It's been working well for me for the past 15 years.

old coastie

To the OP: To soften the ride you might try using the air compressor at your local Lexus dealer. They pump soft air. It works well here in Memphis (and convenient too since the Lexus and Acura dealers are across the street from each other).