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Discussion Starter · #1 ·
I understand the direct correlation between temperature and tire pressure, i.e., rise in temperature increases pressure; however, what I find confusing is the recommendation to increase tire pressure by approximately 3 PSI in the wintertime. It seems logical to me that the decreased resting tire pressure associated with cold weather would be corrected by increasing the resting pressure to "NORMAL", and adding ~3 PSI is actually overcompensation.
I would appreciate a logical explanation of the rational for increasing the recommended resting tire PSI during wintertime.
 

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I believe it is due to temperature ranges. If you hit normal at 50 it is not the norm at 25 or 0. So 3psi gets you in the ballpark for the temperature ranges for the winter.

Or I could google the exact math and try again.
 

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Discussion Starter · #3 ·
I believe it is due to temperature ranges. If you hit normal at 50 it is not the norm at 25 or 0. So 3psi gets you in the ballpark for the temperature ranges for the winter.
But if you checked your tire pressure first thing in the AM when it is likely to be 0 and add 3 PSI to normal recommended pressure, then by late afternoon you'll be significantly above normal.
 

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But if you checked your tire pressure first thing in the AM when it is likely to be 0 and add 3 PSI to normal recommended pressure, then by late afternoon you'll be significantly above normal.
Well you don't do it every day. Or every hour.

This is the first night in three weeks I haven't had to work from home, and you are going to make me google.

*pouts*

I know this I just can't seem to find words in my mushed up brain. All I can say for sure is I set it after work when it gets cold and the range gets me through the winter. I check it after work when it starts to warm up and adjust.
 

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Discussion Starter · #5 ·
Well you don't do it every day. Or every hour.

This is the first night in three weeks I haven't had to work from home, and you are going to make me google.

*pouts*.
Take the night off. Explanation can wait. For clarity I read recommendation in owner's manual for 2009 Lexus 350 RX. Haven't checked Ridgeline owner's manual.
 

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A good rule of thumb is to expect tire pressure to change 1 lb for every 10 degrees of temperature change. I too check mine in the morning on cold tires and set the pressure per the door tag. The minor differences in variation during the day as the ambient temperature rises isn't worth worrying about. But my truck stays outside. My method may not work as well if I kept the truck in a heated garage with a potential temperature difference of 30-40 degrees. Check out the link below for Tire Rack's recommendation on accounting for variables.

Tire Tech Information - Air Pressure: When & How to Set
 

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Discussion Starter · #7 ·
Here's a statement regarding higher wintertime pressures I found that appears to have some logic to it---

....... ambient air temperatures in winter typically range 40- to 50-degrees Fahrenheit colder than typical summer temperatures for the same location. The lower ambient temperatures allow tires to be more efficient at radiating heat and the tires will run cooler, building up less hot tire pressure. In this case, the 3-5 psi higher recommended inflation pressure increase helps offset the reduced hot tire pressures resulting from less heat buildup.
 

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Remember...under-inflated tire heats up FASTER than over-inflated tires. :nerd:

I check mine every 2-3 weeks (plus visual in between)... :wink:

Last I'd "properly" inflated at 35 PSI was when it was around +5 C

Now that it gets towards -12 C ... my resting pressure in the cold morning is at 34 PSI ... sometimes colder then I see 33 PSI (rarely, but will be more as it gets colder )

But here's the thing..as 1st mentioned...about heating time...:nerd:

As I rolled...within 3 minutes...I'm up 1 PSI.... and so as let's say a 20 min. trip...I'm perfectly inflated at 35 PSI !!! 30 min. @ 36 PSI ..etc. ( and this is in minus teens Celsius degrees )

I've always done this with ALL my vehicles... YMMV ! :nerd::nerd::wink:
 

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Discussion Starter · #9 · (Edited)
As I rolled...within 3 minutes...I'm up 1 PSI.... and so as let's say a 20 min. trip...I'm perfectly inflated at 35 PSI !!! 30 min. @ 36 PSI ..etc. ( and this is in minus teens Celsius degrees )
:
If you use the increased tire air pressure associated with rolling/tire flexion to achieve the recommended PSI I would argue your tires are not inflated to the manufacturer's recommendation. The tire pressure monitor on my motorcycle will show the actual air pressure and a second number which ranges from 0 degrees to a "+" or "-" 1, 2, 3 etc...degrees telling me how far the tire pressure, when corrected for temperature, is off the set point.
I do agree with your practice of periodically inflating tires to 35 PSI when the ambient temperature has dramatically changed, up or down, but the logic of adding a few degrees to the set point during the winter escapes me. Again I'm assuming everyone parks their truck outside and inflates tires first thing in the AM.
 

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For me, it's general laziness. I like to set the psi about 3 psi above the number on the door jamb to give me some latitude between tire pressure checks. I don't check my psi as often as I should, but tend to eyeball the tires and use the TPMS as a backup. I've never had the TPMS come on in normal operations except when I've had a puncture. And I've had several of those.

I don't know if the G2 RL uses the same criteria as the G! RL, but the G1 RL TPMS illumination range is ~24-29 psi:
 

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If you use the increased tire air pressure associated with rolling/tire flexion to achieve the recommended PSI I would argue your tires are not inflated to the manufacturer's recommendation. The tire pressure monitor on my motorcycle will show the actual air pressure and a second number which ranges from 0 degrees to a "+" or "-" 1, 2, 3 etc...degrees telling me how far the tire pressure, when corrected for temperature, is off the set point.
I do agree with your practice of periodically inflating tires to 35 PSI when the ambient temperature has dramatically changed, up or down, but the logic of adding a few degrees to the set point during the winter escapes me. Again I'm assuming everyone parks their truck outside and inflates tires first thing in the AM.
I don't think mine is under-inflated...as you read... I inflated mine to the recommended pressure..and the ambient fluctuation is 1 or 2 PSI at -12C after the initial measurement at +5C

if one were to inflated theirs 1st thing in the morning at ambient temp of let's say +20C...which do you think is under ???

again...1 PSI under recommended pressure and takes 3 min at sub zero temp to achieved MFG recommended pressure is very close to "proper"..IMHO :wink:

take example another person inflated to 35 PSI at +20C vs mine as above ( last measured at +5C ) then the temp dropped to -12C...which is under inflated & which is not ??

I do believed however... engineers put it out there with tolerance in mind...so the proper way to properly measure is while cold ( how cold ?? just cold.. 1st thing in the morning fresh cold )..and we all should be fine as the range of difference is within tolerance ( not under & not over )
 

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Discussion Starter · #12 ·
I do believed however... engineers put it out there with tolerance in mind...so the proper way to properly measure is while cold ( how cold ?? just cold.. 1st thing in the morning fresh cold )..and we all should be fine as the range of difference is within tolerance ( not under & not over )
Totally agree we are splitting hairs here and that is not my purpose nor answer to original question. I am curious as to the logic behind the manufacturer (i.e., Lexus and others) stating in the owner's manual to adjust tire pressure up ~3 PSI during colder weather.
Logical explanation may be Lexus assumes all owner's keep their vehicle in warm garage or as cited in earlier post theory that colder ambient air allows tires to dissipate heat more efficiently; therefore, to achieve optimal operating temperature tires should be "over inflated" during cold weather.
My practice is to periodically adjust tire pressure to Honda's recommended set point of 35 PSI first thing in the AM regardless of ambient temperature.
 

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It probably stems from the fact that, although neither under- inflation nor over-inflation is good for the tire/vehicle, over-inflation is generally SAFER than under-inflation. Under-inflated tires run warmer, have shorter service life, and are more prone to blowout. After the legal debacle surrounding the Ford Exploder issue with Firestones, mfrs will lean toward over-inflation.

I always add a few pounds to our cars in the fall (both TPMS-equipped and not). I do not let air out in the spring, however. By the next fall, all tires are a few pounds low again. No, I do not run Nitrogen, except for the 79% or so that is freely available in the air.
 

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It probably stems from the fact that, although neither under- inflation nor over-inflation is good for the tire/vehicle, over-inflation is generally SAFER than under-inflation. Under-inflated tires run warmer, have shorter service life, and are more prone to blowout. After the legal debacle surrounding the Ford Exploder issue with Firestones, mfrs will lean toward over-inflation.

I always add a few pounds to our cars in the fall (both TPMS-equipped and not). I do not let air out in the spring, however. By the next fall, all tires are a few pounds low again. No, I do not run Nitrogen, except for the 79% or so that is freely available in the air
I generally agree with the statements made by longboat except that over inflation is not good for the tire/vehicle. It's not even close comparing under inflation to over inflation (technically a tire isn't overinflated until you exceed the pressure listed on the sidewall). Under inflation can get you killed. Literally every day in Vegas in the summer, someone has a blowout at speed due to under inflation and rolls the vehicle resulting in death or serious injury (and handling a blowout is a whole different topic discussed on the Michelin website).

"Over" inflation in moderation i.e. 5 psi over manufacturers recommendation does a host of good things including a better footprint in the rain, better gas mileage and better handling due to less sidewall flex. This isn't me saying this; this is from personal conversations with engineers from Goodyear and Michelin who collectively have hundreds of years of experience (one engineer from Michelin had 40 years).

So why don't manufacturers just bump up their recommendations? Americans are wuss's when it comes to how their vehicles ride and the squeaky wheel gets oiled. Look at some of the recommendations of European vehicles and generally the psi is higher for a basically identical vehicle sold in the U.S. Make up your own minds but don't just blindly follow the manufacturers recommendation without doing a little bit of research. Might open your eyes. Just saying :)
 

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I understand the direct correlation between temperature and tire pressure, i.e., rise in temperature increases pressure; however, what I find confusing is the recommendation to increase tire pressure by approximately 3 PSI in the wintertime. It seems logical to me that the decreased resting tire pressure associated with cold weather would be corrected by increasing the resting pressure to "NORMAL", and adding ~3 PSI is actually overcompensation.
I would appreciate a logical explanation of the rational for increasing the recommended resting tire PSI during wintertime.
I worked in the tire and service business till retiring in 2012 and never heard of a 3 psi extra in winter recommendation. Al manufacturers tire pressures are based on cold tires, at the lowest ambient temps expected. Of course, most of us don't air up the tires when it's 15 degrees at 4 am. We might wait till later in the day and say, 35 degrees. In this case, you would ideally add a few pounds to the manufacturers cold pressure.

The common "one psi for each 10 degrees F" is close enough but the actual fudge factor is closer to .8 lb/10 degrees F. To figure it precisely, convert the temperatures you're working with to Kelvin and calculate the percentage difference.
 
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