This is the most basic of questions, but I would like to ask some of you folks that if your TPMS lights up, do you fill it up with air immediately or let it fill itself as you drive around?

 

Huh?

You gotta fill it up.

 

I guess the OP is thinking about how the pressure builds due to heat as you drive around. The manual says you'd see about 4-6 psi increase (I've seen 6).

The TPMS trigger threshold (about 27 psi) is below the recommended (33) PSI of a cold tire.

If your TPMS low pressure light comes on... that most likely means you have a leak, unless you've neglected your tires for the better part of a year. Tires are technically supposed to be visually checked every day and then gauge checked every month as per page 273 of the manual.

So yeah, if the TPMS comes on at any time, air definitely has to be added (sooner, rather than later).

 

I've found that tires can lose a lb of pressure a month. A drop in temp also lowers tire pressure. So it doesn't take a year of neglect for the TPMS light to go on.

 

With extreme temperature changes my light come on. Like the 90 degree to 40 degree swings we had about a week ago. But I always pull the compressor out and fill it up before I leave the morning I see it.

 

Basic answer - check your tire pressure first (all 4 tires) so you know what it is and how much to to pump back in.

But before the basic answer - Tire pressure check should be done routinely, at least once a week. Tire pressure check should be done before the first drive of the day, hence the term "cold tire pressure check". Also should be done more frequently with temperature changes like now.

Just my take.

 

you're right, it wouldn't take a year.

by "better part of a year" I meant more than half. But even so, it might only make it that long if its a warming trend (winter into summer).

I look at my tires every chance I get... last thing I need is to have a flat during a delivery. I'll use the gauge maybe once or twice a week too.

 

Don't wait for the TPMS light to come on. It's only on when the psi is below a set threshold (as mentioned earlier by someone else) which is already a good amount lower than the manufacturer recommendations. It's only useful for people who neglect their cars in most cases, unless the tire pressure suddenly drops in the middle of driving, though anyone with a pair of hands would notice it since the steering wheel would need to be turned more to offset it just to drive straight.

Personally, I check my tire pressure at every fill up or before a trip (say, more than 50 miles, even though I usually fill up before such a trip anyway). I'll always adjust my tire pressure to where it needs to be, assuming it's off by more than 1 psi, though oddly I can usually sense a tire having low tire pressure from behind the wheel, assuming it's off by 2+ psi.

 

Very informative answers, folks. Thank you!

 

Just remember, your tire pressure will be a bit higher if you check after you've driven the car.

 

^ While that's true, if the tire pressure of one tire matches the tire on the opposite side (left to right, since a lot of cars have different tire pressures from front to rear), then you're probably fine, assuming that both tires aren't off.

 

time/temperature caused PSI drop would be relatively even across tires.

so warm tires on an abnormally warm day may (appear to) have sufficient pressure... but be well below once it cools off the next day which could be a ridiculously cold day (Welcome to Chicago!).

take my experience... on the Pathfinder, in an attempt to get a softer ride out of the stiff suspension... I let some air out. I think dropped it to about 30 PSI, but that was after driving around for a few hours doing deliveries on a cold, COLD winter day. Next day, I woke up to find the tire FLAT. Apparently, the PSI change when the tire cooled off was enough that at the lower pressure, there wasn't enough holding the seal with the way the tire was deforming (imagine the shape of a tire as it is under-inflated)... so it separated and let the remaining air out.

 

fill it up in the morning to about 32-35 psi (or whatever the factory recommends on the door jam) The psi changed as the temperature/driving conditions change. If after you fill all the tires with the correct psi and the tpms light is STILL on, drive around for a bit after the tires warm up the tpms light will reset and you will be a-ok ^^

 

yep, just remember 10F in ambient temp change results to about 1psi in your tire.

so if your tire was 32psi in the summer at 80F, your tires will be at 28psi or a tad lower at 40F. and vise versa. when i check tire pressure i keep notes in my phone the date, temp, and psi i used. this way i can tell by drop in temp when i really need to start thinking about pumping more air in.

in the spring i need to let air out as psi will continue to rise until summer.

 

Good to know. Thanks everyone.

 

while there are cars that have built in compressors the fit is not one of them; you must add air yourself using a portable compressor or typical gas station, which may charge a quarter.
when you add air use your pressure gauge to verify the air pressure and not depend entirely on the station gauge.
refill typically to 35 to 40 psig, and at least check weekly.
forget about the pressure build upwhen driving or atmosphere; depend on checking them cold for baseline. if you've been driving and tpms light comes on start looking for a station with air compressor if you don't have one you carry with you.
nobody ever says a car doesn't require a lot more maintenance than a computer.

 

Using the same gauge every time helps for consistent readings too. So carry your own and use the same one every time.

 

I use this gauge, very accurate

http://www.summitracing.com/parts/mo...MobileSwitchNo

Since I park outside I check my pressure every week and normally keep it at 35-37psi. I also have my own portable air pump that I bought from Harbor Freight