itzsteven

lately it has been very cold in my area , and when i took my ralliart out to drive in the morning to school, a warning low tire pressure popped up in the dash, but after around 30 mins of riding, it just went away. ive checked the tire pressures later taht day and everything seemed fine, the door said tire pressure was 35, which i meausred in each wheel. but then i woke up the next morning and when i started up the car it had the same low tire pressure sign, then went away after going on the freeway, my question is , is this normal?

C2Rally

one or more of you tires are probably boarder line lower (or higher) than the others, when its cold, things contract, steel, plastic and of course air and rubber, when you are driving the tires then have a chance to heat up from the road friction, this would likely bring the tire temps up and equalize the pressures inside the tire enough to make the light go out. With out knowing where your car is or what tire pressure they are at Before you go anywhere I"m just speculating. This is a likely cause though, hopefully nothing serious

LancerEVA06

iTrader: (3)

If you have just plain ol' air in your tires, when it gets cold, you'll drop pressure, causing the TPMS light to come on. Driving around warms up the air, and causes the pressure to build back up to normal. My suggestion is fill up with nitrogen... most places do it for less than $10 and will check pressure and fill as needed for free afterwards (in my area anyway)

aestival

Both air and nitrogen contract with temperature -- there's no advantage here at all to nitrogen (all that nitrogen does is improve rubber life, on account of not containing any oxygen). Going from 20 degC (68 degF) down to -40 degC (-40 degF) would reduce a tire pressure of 40 psi to below 32 psi. It's wise to get your tires inflated at or near the ambient air temperature, and to check the pressure frequently when the temperature is swinging wildly around (as it sometimes does in Spring and Fall, or all Winter long, in unlucky places such as Calgary).

[incidentally, if you really want to fill up your tires with something inert, then use argon, not nitrogen -- personally I'm sticking with air, because I never have tires keep their tread past two years, so there's no real chance of tire rot from oxygen in air]

itzsteven

ah i see, alright thanks guys. actually when i checked the tire pressure on the tires yesterday, one was at 40, so i think that might be the reason.

eg6motion

it doesn't expand or contract as much as just air in the tires. Same goes for people who play paintball and use nitrogen...doesn't fluctuate psi in varying temps like co2.

Heliart

the factory recommended tire pressure on the door is the cold pressure so if you fill your tires up to 35psi in cold morning you'll be fine

EVO Neil

iTrader: (6)

Someone has already touched on this...it's cold pressure. If you've driven the car even a few miles that number goes out the window...add about 3 pounds more when checking them hot. So if it reads 35 psi on the sticker and you check them hot, set them to 38 psi

Also tire pressures go down 1 psi for every 10 degrees in outside temperature and vice versa up 1 psi for every 10 degree raise in outside temperature.

So most likely you checked the tire pressures when the tires were hot and figured it was correct but was really 3 pounds low and then overnight the temps went down further lowering the tires psi to a light-triggering low. I hope that helps.

Robevo RS

iTrader: (16)

i hate that.
I will take out the TPMS warning light from my dash .

EVO Neil

iTrader: (6)

That light could very well save your life...if you picked up a puncture at speed and didn't know your tire was going down, that light could be the difference between a bad incident or worse and you knowing you should stop and check the tires.

I'm not sure if it starts in 2009 or not, but all cars will be required to have some sort of TMPS. Think of how many lives during the Firestone tire/Ford Explorer debacle that light could have saved.

Robevo RS

iTrader: (16)

you feel it if the tires loosing pressure. If the TPMS is the pivot point for my life then be it
I drove and raced over 20 year without TPMS. I think i would be fine without it.
Just like the DRL. We are not in Scandinavia.

TruboPower

Actually it was mandated in 07'

dboz

iTrader: (1)

Throw the baby out with the bath water

aestival

Air is not carbon dioxide -- it's about 78% nitrogen, 21% oxygen, 1% argon, and very little else. All three of those gases expand and contract exactly the same at any temperatures and pressures that you're likely to encounter in everyday life, including in tires. Carbon dioxide is different, but I'll spare you the details.

The only difference in the big three atmospheric gases is that oxygen is hideously reactive (i.e. it reacts with things to make them burn and rust), while nitrogen is not very reactive (except with oxygen, mostly), and argon goes beyond even nitrogen to being practically 100% inert.

Sorry for the chemistry lesson -- lecture mode off

aestival

What light? My Ralliart would just warn me on the info screen (it did when I drove my car off the dealer's lot, just after it went from inside to outside, haven't seen that message since).