Low tire pressure light...
 

Today was the coldest day we've had so far this year where I am in Tennessee. I went out to scrape the ice off the BRZ's windshield while the interior heated up. Once I finished and got back into the car I noticed the low tire pressure light on, on the dash.

http://i239.photobucket.com/albums/f...ps2jefpe3p.jpg

When I left work today it was still on, but it went out sometime on the ride home.

Are the TPMS sensors temperature sensitive? I've had other cars with TPMS but never had this happen before.

And before anyone tell me to use the :search: button... it doesn't work lol

It usually goes on when it's cold outside. You can usually tell just by looking at your tires that one of them will be a little lower. Just go add a little bit of air to the tire and the light will turn off on the dash. May take a few minutes to register.

PV = nRT

Yep. Cold weather will almost always set them off. If they don't go back out after a few minutes of driving then check the pressure.

No, but the air in your tires is. Cold = denser air = less pressure in tire.

Similarly, this is why you should air your tires out a bit before tracking. Once they get up to temperature, you'll gain a few PSIs.

A. Cold outside temperatures reduce tire pressures (PV=nRT, high school chemistry ftw), add air.

B. http://www.ft86club.com/forums/showthread.php?t=24176

Or drive for a few minutes and let the air warm up and the sensor shut off.

science
 

Cold air shrinks and hot air expands since it got cold out the pressure in your tire rated in PSI went down below the TPMS threshold which is normally a 3-7 PSI range. The light will go off(maybe) after enough driving on them from the friction of the tires on the road heating up the air inside. Just make sure to check you tire pressure in the morning before you leave and then fill them up to whatever is says inside the driver door in the door sill near the latch. Fill it up 1 or 2 psi above this and you should be fine.

Or warm 'em up the old fashioned way.

https://49.media.tumblr.com/17827211...r3c4o1_500.gif

For max tire life and safetly, check your tire pressure once a month before you drive it for the day. Cold tire pressure should be 34-35 psi. When it is getting cold outside, the pressure tends to be lower (basic physics) so check them more often. Also, when summer comes back, make sure the tires are not suddenly over inflated because of the temp change outside.

Don't forget the front.


http://www.carthrottle.com/wp-conten...011137_530.gif

Totaled

After driving 20+ miles to work with an average speed of 60-65 mph and the light not going out I was scratching my head. But that same trip back home in the afternoon it went out sometime along the way.

So figuring it was temp related, but wanted to make sure with you fine folks :D

Yep, I think the approximation is like every 10 degrees = 1psi. Rough approximation.

Btw, related but slightly OT, does anyone know if the TPMS actually updates during the ride? Or does it only update on engine start? To me, it seems like it only checks pressure on engine start. I don't think I've ever had that light go out mid-drive.

Anyway, I just picked up a Vivair portable compressor that runs off the 12v accessory port and a digital tire gauge. Cost me $50 after tax from Amazon.