Shalooby

OK. I've searched for an answer to this and can't find it. I've heard that tire pressure should be checked when the tires are cold, right? Should they be set to the recommended pressure when cold or should the rise in pressure after they have warmed up be taken into consideration when setting cold pressures? Here's my example.

Cold pressure in the morning before moving the car is 30 psi.

After 10 miles or so the pressure is 34 psi.

If I set the pressure to 34 when cold then they will increase to 38 when warmed up. Don't I want the tire to be at the recommended pressure when it's warm? Why is it recommended to set / check tire pressure on a cold tire?

Thanks for any insight into this. Sorry if it's confusing. Also, above pressures are purely for the sake of simplicity.

erdoc48

Tire pressures should always be set when cold (less than 3 miles driving or when car has been sitting at least 3 hours). Also, they drop in pressure roughly 1 PSI for every 10 degree temperature drop, so that's why it's recommended to check them monthly. The 06 TL has the TPMS so you can check them from the dash.

CL TYPE SPORT NAVI

tire pressure should always be checked and filled while cold. this i belive is somewhere in the owners manual i belive. if you do this while tires are warm then u have more of a chance of getting cupped tires or uneven tread wear.

erdoc48

Addendum: I had mine set to 30 PSI recently, and didn't like the ride (with lower temps. in NJ recently). I jacked them up to 36 PSI, and like the ride much better. It even seems to ride better, well, to me anyway. You can use the door jamb pressure listed in the car or the manual, and then decide how you like the car to feel when driving (use the door jamb listed pressure as the minimum). Just remember, always cold!

yohan81718

my dealer keeps on setting to 32psi all around when the manual says 35psi on the front and 32psi on the rear for 6MT.. I had to argue to get it to that psi -_-

chill_dog

^^^ Makes you feel good when the dealer doesn't know the tire pressures for your car, doesn't it? Thankfully my dealer leaves mine alone.

Oh, and to go along with everyone else, check and fill the air when the tires are cold...first thing in the morning is always the best.

Will Y.

I like slightly higher tire pressures (36F/33R on my 5AT now), so I tell dealers and even my own independent mechanic to use a specific pressure if tires are rotated, or tell them to leave the tire pressures alone if no rotation. Then I check pressures later.

Shalooby

Thanx for the information. Here's what I've gained from this.

Operating pressure is higher than set pressure. I've got an 06 AT with the TPMS. Before I roll out in the moring the system dispalys 30 psi at all four corners. After driving for 10+ miles it displays 33-34.

So... if I set the pressure when cold to 34 psi the actual operating pressure is going to be 37-38 psi. Correct?

chill_dog

Yes.

SouthernBoy

Ideal time and method to use is: 1) early morning after the car has sat all night; 2) in a closed garage; 3) use a high quality tire gauge (don't go cheap here).

Barring a garage, check pressure in the shade and/or before the sun comes up. Remember, tires on the north side will register slightly lower than those on the south side.

S PAW 1

Hey, Southernboy
What if the breeze is coming from the south?
)))))))

SouthernBoy

I just knew after I posted this that I would get some flak. I deserve it, I suppose.

Seriously, I was taking it to the extreme for those who want to know the extreme. I can tell a 4 psi difference in my TL. When I picked it up, the left front tire was down 4 pounds. The lowest pressure difference I could tell in any car I've owned was 2 pounds in my 1988 Mustang LX 302 CID. That is unusual in my book.

Now IF the breeze is Southerly, then it can only be a good thing... right?

S PAW 1

Yep, Southerly is good!
Just some friendly ribbing.
My wife will tell you I am soooooooo anal about tire pressures.
Last Xmas I bought a box of cheap pencil gauges, and left one on cars (especially SUV's) that had obviously low tire pressures. Might have saved a life, let alone
some gas. Might do the same this year. Even with the price of gas, many just don't get how important those pressures are.
Now, for my anal buddies (or soon to be), never, NEVER, trust pencil
gauges. Use the brass ones. More money, yes.....but worth it.
Happy Trails!
'05 6MT NBP
A Spec suspension
K&N Typhoon intake
V1 on the lookout

slapmesilly

I am curious, how accurate is the TPMS system compared to the brass and pencil gauges?

jgrahamiii

Having read this thread, it's clear that different temperatures outside yield different pressurs in the tires. You are supposed to match the door jamb pressures when the tires are "cold". But what is cold? Last saturday, cold was almost 70 degrees in NY, but today it is not above 35. That's more than a 3 PSI difference according to at least one post. Any given day can see a 20 degree rise in temp (2PSI) .And in a garage, as suggested, the temp may be significantly higher than outside. Now I can't believe I should be adjusting my tire pressure as the day warms up outside, or from day to day. Maybe month to month, or season to season.

So what do we do? Estimate an average temp for the month and try to test on that temp (or use the 1 PSI/10 degree rule and adjust)? Are we better off assuming a little lower or a little higher?

Prior to having the TPMS in my TL, I obviously didn't know better, but now I see the PSI every morning and afternoon, and they are widely different day to day, as the temp changes. I've checked TPMS against a gauge and it is pretty accurate.

Thanks for any advice. -John

Adobeman

There is always going to be some degree of uncertainty. Unless you start chalking your tires and/or measuring tire surface temps (yea sure ) you will always be playing an approximation game. While all that may pay dividends at the track I seriously doubt it's worth the worry for the every day driver.

I have a good dial gauge and check them first thing in the morning (pretty much exactly as southernboy says). It's just that simple IMHO. As long as the morning temperature is relatively average for the time of year you will be fine. I don't have TPMS but I'd think a driver monitoring it while your driving is a bit overkill. I'd want it to show me the temps at start up and so I could see any variances and only bug me if and when it sees different rates of change in tires as in one going flat.

avs007

A lot of the variance is because of a high moisture content in the air in your tires. After I got my own compressor, and installed an in-line line dryer, I stopped getting such wildly varying pressures with temperature.

Some of the air-compressors at gas-stations are really bad. I've seen some that sprayed out so much water vapor, you can actually soak your hands in water as you spray them.

Will Y.

I agree with the two prior posters. Simple answer: put in air to recommended psi + 2 lbs in each tire on a 40. degree F morning when the car has not been driven within the preceding 4 hours. Ignore the TPMS pressure readings after your car has driven for 5 minutes or more, unless a warning pops up.

The ways to minimize temp fluctuations due to moisture, etc. are to either 1) deflate your tires and use your own compressor, or 2) deflate your tires and fill with nitrogen IF IT IS FREE (at Costco with new tires) or only nominal cost; this last step is probably overkill for a street car and is more of a psychological palliative to those of us with OCD (which is probably most of us on Acurazine... )