getakey

Last night, temp got lower than it has been 65 degrees

Left early in morning and had low pressure warning. Turned to pressure settings and 3 tires were at 28psi, 1 at 29 psi. Warning was on one of the 28psi - left front

Didn't have time to stop so left thinking it would warm up and increase. Tire pressure gradually increased over abut 30 minutes to 32 psi on both fronts, rears went to 30.

Warning did not go away until 32 psi reached. Outside temp actually got lower to ~60 in direction I was going. It was all highway driving. Do you think steering even on highway caused fronts to increase more or more influence from engine temp?

2012wagon

When you are driving on the highway, that is what caused the PSI increase.


A typical tire revolves roughly 750 times as it travels a mile. At 60 mph, that's 750 revolutions per minute. As the miles roll by, the tire gets hotter, which is why the tire pressure increases by about four pounds per square inch (psi) after a tire has been driven for a while.


Typical tires experience a temperature increase of roughly 50 degrees after running on the highway for a half-hour. If it's a 70-degree day, this suggests a tire temperature of about 120 degrees.

getakey

I realize the change was due to friction, but was there added friction on the fronts versus rear or was there also some influence from the engine compartment?
Black tires - black fender well - radiation could be a factor from the engine

wstr75

I find, particularly with the larger tires on my GMC truck, the tires exposed to sun also show a pressure difference on a cool/cold day. My truck tires have probably 2X more sidewall exposure than my RLX and thus have more exposed surface like a solar panel for absorbing the sun's photons. On a cool morning last week, the truck's tires on the sunny side were 2 psi higher than the ones on the north side. I plan to repeat the "experiment" with my RLX to see the effect of sun exposure on a cool, bright day.

getakey

saga continues
this morning a bit colder at 56
3 tires at 27, 1 at 28
Warning for left front at 27. No warnings for other tires.
After work, temp 80
all 4 tires at 30
Warning still for left front

Why is only the left front giving warning? First time warning at 28, but only for left front
Second time, all 4 tires at 28 or lower and only warning for left front

getakey

saga was poor use of words
really more of curiosity continues

2012wagon

Why not pump all the tires to same psi and see if your saga still continues

thoiboi

well all your tires were under inflated to begin with.. Isn't the recommends PSi 36 COLD so in the morning, you should inflate your tires before driving them.

getakey

36 psi Cold? I doubt that, but will check

We've had a very hot summer and just now transitioning. Yes, I need to add some air, but up until now they've been running 36-38 all day.

Was just at the Dealer for service, so should have checked and topped off if not right then.

They are all at the same temp - that's why I don't get why only one tire throws the alarm

thoiboi

35 or 36.. check your door jamb.

RDX-Rick

The owners manual doesn't specify at what pressure the alarm will be activated, it only says the light will come on when one of your tires is significantly under-inflated.

According to the Firestone website the recommended pressure for your tires is 35 PSI. I don't know if a 7 PSI drop to 28 is considered significant, but if the light stays off when you refill the tires to 35, then just consider yourself lucky that you have an early warning system.

In other forums I have read that once the "switch" inside the wheel sensor has activated, the tires need to be inflated a little more than normal to reset the switch. Once the alarm has been reset you can release a little pressure to return to the correct level. Of course this information was for a Toyota that only had an alarm light and did not display actual pressure readings.

BTW my front tire pressure also rises about 15kPa (about 2.2 PSI) above my rear pressure

getakey

I've noticed the alarms tend to be "sticky" even in the older RL
Just seems odd that the left front is super sensitive and the others are not.
No big deal, just curious

holografique

The defualt OEM PSI for the PAWS RLX is 35F/33R Cold, as indicated on the sticker on the driver-side door jam. Which typically should level out to 39F/37R after driving.

I have found a 33F/33R Cold to be better at handling and dampens some of the effects of the faulty suspension design of the pre-2016 PAWS models.

getakey

I'm thinking the higher increase on the front versus is rear is because of FWD. There is force applied through front tires, not rear.
Keep in mind that my tires were all the same psi when I started and front tires final temp was 1 to 2 degrees warmer than rear
Will bring them up to the "winter" settings this weekend

RDX-Rick

I have AWD and my front tire pressure will increase about 10-15 kPa (2 PSI) more than the rear tires.

My theory is that tire flexing causes heat buildup, and heat buildup causes an increase in pressure. The fact that the front tires are steering causes more flexing in the front tires and therefore more heat and pressure.