4 psi loss?

My TPMS light came on. Tire Pressure Monitoring System. All 4 tires were at least 4 or 5 psi too low. I know I can’t have 4 nails in 4 tires so why did I lose so much air?? Filled up to 35 psi on stock tires and light went out. 2006 Nissan Frontier 2wd 29500miles.

When’s the last you checked tire pressure? Tires can lose pressure over time. If you haven’t checked them, that’s what the TPMS did for you.

Perhaps a change in weather. Air pressure drops as temperature drops.
Perhaps a normal variation in the accuracy of the two measuring gages.
Perhaps normal permeation. Air does work its way out over time, albeit slowly.
Perhaps you’d been running the tires at faster speed or on hotter macadam before measuring. That affects the temperature of the air inside, affecting the pressure.

How long has it been since you last checked? Two years?

If they’re all the same, you have nothing to worry about, it’s normal variation. Just monitor them more often.

Where I live, the temperatures have already been dipping to the low 50s at night, on occasion. Did the TPMS light come on in the morning?

If the tires had previously been inflated on a day when the ambient temperature was in the 90 degree range, a 40 degree drop in temperature would result in a loss of 4 lbs. in pressure.

The lesson in all of this is that it is not a good idea to rely on the TPMS, since it is obvious that it took a fairly large drop in pressure to illuminate the light. When the pressure dropped by…let’s say…three lbs., you were already losing some fuel efficiency, the treads were being subjected to accelerated wear, and your handling was already not as good as it should have been.

If you personally check the tire pressure every 2 weeks or so, you can pretty well assure yourself of keeping the tire pressure within a fairly narrow range, which is better for the vehicle and for your wallet.

Did the weather turn colder? Did you fill them the last time after driving some? Like you said, unlikely they all got a nail, but they may have only been 1 psi above the trigger point before.

I agree with the previous posts.
I have to add several psi to our car tires every year as summer draws to a close. I have already done ours. It amazes me each time how much the tire pressure had dropped.

If you live where the temperatures are starting to fall then you should be all set. You can be sure by checking the pressure regularly. My experience tells me that this one large end of summer change is the big one and the tire pressure should become more stable now.

Also, it amazes me that I never seem to have to let out air in spring/summer because of expanding air.

Check them “cold” each time before heating them by driving on them.

Yep colder weather will drop it at least that much. Cold air is denser than warm air so as the temp drops so will the tire pressure. That’s why its easier for planes to take off in the winter than summer.

yes sir,my 2007 nissan frontier does the same. no problem, just filled it to 35 psi and the light goes out after you drive it a short distance.

True about the planes demonstrating this. Every pilot is trained to calculate the relative differences in take-offs at high/low temps and the role of the altitude and humidity of the airport. A take-off in Devnver (Mile High City) on a hot, humid day can require 2 to 3 times the roll distance compared with a near sea level airport on a cold, dry, day, Yikes!

Humid air is less dense even though people wrongly say the air is “heavy” on a humid day.

I used to fly small planes and on a cold, dry, winter day it sometimes felt like I had a supercharger!
Come to think of it, my Honda 305 Superhawk did that, too!

The air density acts on both the wings (lift) and the engine (power).

This goes for little guys and monster airliners, too.

It’s unlikely that you have nails, or anything else, stuck in your tires. ALL tires lose pressure over time. Air molecules seep out through the tire. Pressure changes with air temperature. There are lots of reasons. That’s why you should develop the habit of checking the pressures periodically. Correctly inflated tires increase fuel mileage and vehicle safety.