lightonthehill

The eight tires on my two vehicles all had 35 pounds (front) or 33 pounds (rear) in early September, when the temp was near 90 degrees. This pressure had remained fairly constant all summer.

The weather turned cold (34 degrees this morning), so I checked my tires. The highest four were 28 pounds, and the lowest four were (UGH!) 26 pounds.

If you haven't checked your pressure since the weather turned cold, please do so very soon.

04SEelite

Great advice Light - I did check mine and found that the backs had sagged to 28 down from 32, and since I had the car at the Goodyear store over the weekend to get one of the RSA's replaced under warranty, they had inflated the fronts to 34, so not sure if there was a loss there but suspect that there was...

NismoMax80

iTrader: (6)

I always check mine cold (in the morning before driving) anyway. So I thought there shouldn't be any change. I check them every few weeks and always have to add a little to bring them to 32.

MaxMus

do you guys have an air compressor at home or something?

lobewiper

Yes, but you can buy the kind that operate from your 12 volt outlet for 15 to 20 dollars. They are slow pumpers, but get the job done and can be very handy if you're somewhere far from a service station and don't want to have to change to your spare in the dark.

Banditman

And you don't

Banditman

NismoMax80

iTrader: (6)

$10 Walmart. plugs into the car. when I have $$ I'll look for one with the gauge on it.

lobewiper

Save your money and buy a decent separate gauge. I've found errors of as high as 25% on the two 12 volt compressors with built-in gauges I've owned. (Be sure to get the compressor with the built-in coffee maker, jk)

NismoMax80

iTrader: (6)

oh i have the best separate guage there is. would just be nice to know how much I put in instead of on and off checking. valvelock.net is the gauge i have. a little tricky to master, but won't let air out unless you press the release button.

Banditman

The problem here in florida is that it can be 50 degrees on the way to work and 80 degrees on the way home from work. Makes it difficult to decide where to set the pressure.

Banditman

NismoMax80

iTrader: (6)

that's why the cold pressure recommended is 32.

for SE that is, SL should have a cold and hot psi too.

MaxMus

yeah, i have a small one from my 2000 but that thing take 1/2 hour to pump up one wheel.

SEmy2K2go

iTrader: (10)

I checked mine this moring. My 19" 35 series Nittos had been feeling kinda "soft" and I guess 24 lbs would cause that. Good thing I filled them up a few days before going back to the OEM wheel/tire combo

PETZUK

The general rule of thumb is a 1 pound change in pressure for each 10 degree change in outside temperature.

I would suggest checking tire pressure every 2 weeks. You'll be surprised how much loss occurs according to your driving habits (cornering, braking, etc.). Do it when the tires are cold and they have not been in direct sunlight. The sun's warmth will increase tire pressure.

Checking pressure every few months is not enough for maintaining proper pressure.

lightonthehill

PETZUK is right. The pressure will drop gradually at all times, but particularly quickly as the weather turns cold. Checking every few weeks is not too often.

Banditman - if your tires are at the proper pressure when they are cold, then it doesn't matter how high the presure may go while you are driving.

NismoMax80 gave us the recommended cold psi for the SE (32). The SL recommended cold psi is 33.

On my SL, I carry 33 in the rear, but 35 in front, as the front is where over 60% of the weight of the car is located. Also, the front does all the pulling, most of the stopping, and all the turning. This means, of course, I have to adjust the psi whenever I rotate.

NismoMax80

iTrader: (6)

okay Light, so what about the arguement that the weight shifts back when travelling? (then of course it shifts forward when braking). And can't you influence over/understeer by having different pressures?

I check mine about every 2 weeks and always before long trips. NEVER set them at the psi on the tires that is the maximum. [I guess if you are carrying/pulling an excessive load you may want to?] Some like it high(er) but it is suggested to run below that. (I would assume as a basic rule, run 4psi below maximum if you are unsure?)

lightonthehill

NismoMax80 - I haven't heard the one about the weight shifting back as the car is travelling. I would think there might be a momentary backshift of weight during acceleration, but, once moving at speed, I would expect the weight on the front tires to be clearly more than on the rear. Of course, sometimes my expectations are not met.

As to the oversteer/understeer bit, if the front tires both had like ten pounds higher pressure than the rear, that would cause the front tire sidewalls to be more stiff than the rear tires, which should let the rear move laterally more than the front (clearly resulting in oversteer). But I haven't noticed oversteer with a difference of two pounds. Probably because the extra weight of the front of the car results in the tires with two extra pounds having essentially the same profile as the rear tires.

I feel the 'proof' of this last statement is that, when all four tires have the same pressure, the front tires appear to show more sidewall flex than the rear tires due to the greater weight on them.

As to running with higher pressures, like you, I would never run tires at pressures greater than the maximum specified on the tire. For many years, the maximum on many tires was 36 pounds or so. But modern tires have higher maximums. For instance, the OEM Contis on the SL have a maximum pressure of 44 or 45 pounds (I'm too lazy to turn off the security system and go to the garage and see which).

I would not consider using a pressure anywhere near that maximum. Under normal driving, I would feel any pressure over 37 pounds or so would result in the tires wearing out in the center before they wear out on the shoulders.

One caveat: Running two pounds extra in the front tires offsets the extra weight up front, making the car completely level. This results in the top edge of the low HID beam moving up very slightly; say from the seat tops to the inside mirror of a car about fifty feet in front of your car. Necessitates a very slight downward adjustment of headlights.