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Old 01-16-2015, 10:42 AM   #1
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Do you compensate for temperature when setting tire pressure

I just turned on my TPS this morning and all of my tires are measuring about 4psi lower that yesterday afternoon.
The difference is that this morning the temperature is about 49 deg, and yesterday afternoon it was about 70 degrees.

So my problem is what is "tires cold" when adjusting tire pressure.
We make a big deal out of finding the right PSI in the load charts, but then this comes along and I no longer know what PSI to set in the morning.

any suggestions?

Dan
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Old 01-16-2015, 10:54 AM   #2
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I may be way off on this but I believe what is meant by tires cold is what pressure is in your tires when they have been sitting for more than 12 or more hours. example in my mind would be you drive for 8 hours or so and arrive at your campsite, you check the psi in your tires the next morning before your next trip. That to me is tires cold. I do not believe it has anything to do with ambient temperature. I think it means the tire is cold (not warmed up from running down the highway).
That being said, I do realize that the first time you have colder weather than normal I usually have to put air in all my vehicles tires but never have to add air later during the winter.
If I am wrong someone please speak up.
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Old 01-16-2015, 11:07 AM   #3
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My Jeep tire pressures drop from 37 to 30-31 when air temps go from 60 to 0. Temperature makes a real difference. Tire MFG usually specs a temp and pressure, or lists pressures at standard temp.
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Old 01-16-2015, 11:12 AM   #4
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Camato5 is close. You don't need to sit for 12 hours.

"Cold" inflation means:
1. Not having been driven more than 1/4 mile in previous 2-3 hours.
and
2. Not being in direct sunlight for the previous 2-3 hours

We are not talking about a Chem Lab or Physics Lab experiment where we set temperature and atmospheric pressure to some special "standard" condition. We mean the tire is at the same temperature as the air outside.

Now some will take this to an extreme and try and ask about being parked at 12,000 feet in sub zero conditions when they are planning on driving to the bottom of Death Valley where it is 130F. Under normal conditions in normal travel there are no special adjustments for temperature or elevation that need to be considered. I have covered both temperature and elevation in posts on my tire blog.

If you are under the extreme conditions mentioned above pleas PM me and we will work out a plan for proper inflation procedure.
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Old 01-16-2015, 11:16 AM   #5
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Quote:
Originally Posted by RandyMWV View Post
My Jeep tire pressures drop from 37 to 30-31 when air temps go from 60 to 0. Temperature makes a real difference. Tire MFG usually specs a temp and pressure, or lists pressures at standard temp.
Nope. If you read the literature from tire companies they refer to atmospheric temperature not laboratory temperature.

Normally most tire pressure will change 2% for every 10F change. You can read the Science in THIS post.
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Old 01-16-2015, 11:21 AM   #6
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When I leave for my summer trip.
I check all in the day time(In the 80's) a couple days before my trip North where the day temps will average around 20-30 lower. And nights up to 40 lower.

So I put in around 11-13 PSI more then my weight requires.
Then on the first night it is around 40 colder and the tire monitor goes off.
I reset all sensors and then they are good for the whole summer and need no more PSI adjustment.

That has worked for me over the last 12 plus years.
When back to my winter spot. I increase the PSI to 120 and then the next spring let air out to the above settings.
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Old 01-16-2015, 02:37 PM   #7
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tire pressure advice is to take care setain area's of the rubber of tire dont get to hot , so they harden and damage in next bendings.

When it s colder outside the tire , the tire inside is also colder so those critical area's are cooled down better , so at colder ambint temp the tire can produce a bit more heat and still be save .
This more heat is produced by the more deflection of the tire at the lower pressure at lower ambint temp.

If this more heat production is totally in line with the better cooling I dont know.
But if you keep enaugh reserve in the pressure , dont worry about the lower pressure within normal conditions . Extreme conditions in temperature probably need adjustment.
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Old 01-16-2015, 02:53 PM   #8
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Quote:
Originally Posted by Tireman9 View Post
Camato5 is close. You don't need to sit for 12 hours.

"Cold" inflation means:
1. Not having been driven more than 1/4 mile in previous 2-3 hours.
and
2. Not being in direct sunlight for the previous 2-3 hours

We are not talking about a Chem Lab or Physics Lab experiment where we set temperature and atmospheric pressure to some special "standard" condition. We mean the tire is at the same temperature as the air outside.

Now some will take this to an extreme and try and ask about being parked at 12,000 feet in sub zero conditions when they are planning on driving to the bottom of Death Valley where it is 130F. Under normal conditions in normal travel there are no special adjustments for temperature or elevation that need to be considered. I have covered both temperature and elevation in posts on my tire blog.

If you are under the extreme conditions mentioned above pleas PM me and we will work out a plan for proper inflation procedure.
Tireman9 has it right.
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Old 01-16-2015, 03:24 PM   #9
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I just always stay where it's warm. (-:
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Old 01-16-2015, 05:50 PM   #10
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The ambient temperature absolutely has an effect on your "cold" tire pressures.

A simple rule of thumb is 1lb of tire pressure for every 10 degrees. For instance, if your took your "cold" tire pressures (not driven on all day for instance) in the afternoon and it is 70 degrees, and then you check them in the morning when it is 40 degrees, you'll see about a 3lb drop (just as the op and Randy noted).

The sun heating up the tire carcass also has the some effect. So, if you did those afternoon tire pressures when it is 70 degrees, but 2 tires are in the direct sunlight, they may really be 80 degrees, so in the morning when it is 40 and the sun is not up yet, the shady tires will be 3 pounds low, and the sunny side tires may be 4 pounds low.

So you should take into account the temps you expect to be driving in. If you start a trip in NY in January and it is 30 degrees when you set your pressures, you will want to adjust them down as you head south as you get to warmer temps. Same situation if you take the temps of your car in a heated garage when it it 40 degrees colder outside - you'll want to be about 4pounds high in the garage, but if you know on average it's generally going to be 20 degrees colder outside, you'd set them 2 pounds high in the heated garage.

You don't need to get carried away with it, just be cognizant of it and manage your pressures accordingly.

Regards!
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Old 01-16-2015, 05:54 PM   #11
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Old 01-16-2015, 06:03 PM   #12
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I just pick a cold day to put the monitors on and no I do not compensat, If I need to add air, I try to do it first thing in the AM when it is coldest.

But that is me, others may do it differently.. I do not feel working out the math (Even if it is easy) is worth the trouble.
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Old 01-16-2015, 06:06 PM   #13
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If you check and adjust the psi before you drive "every time" it wont matter what the temp is.
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Old 01-16-2015, 08:03 PM   #14
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Quote:
If you check and adjust the psi before you drive "every time" it wont matter what the temp is.
Isn't that "compensation"? For temperature and any/every thing else?
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