[Ron Fuller]

We will be traveling thru Colorado soon. What is the consensus for elevation changes and air pressure?

A Google search using the following: site:gl1800riders.com/forums tire pressure altitude will show some past threads on the subject. Tire pressure gauge reads about .5psi higher per 1000' increase in elevation.

Ron Fuller

 

[NJREF]

Goodness.....some on this forum really like to worry about things they needn't worry about....nonetheless for the record:

Universal gas law

PV = nRt

pressure x volume = number of moles of gas x gas constant x temperature

R = 8.314 joules per degree Kelvin
T is absolute temperature (degrees Kelvin)

As temperature increases so does pressure at constant volume....the more gas the higher the pressure (WOW!)....I am guessing that the tire manufacturers are aware of this amazing scientific fact and have taken it into account when publishing cold tire pressure requirements
AND
I bet they have done all sorts of measurements and stres tests on the tires taking into account lots of variables

For me....I check pressure in the AM.....very, very occassionally I have to add some premium 78% nitrogen blend....this has worked for the last 30 or so years of motorcycling

 

[05nwl]

Goodness.....some on this forum really like to worry about things they needn't worry about....nonetheless for the record:

Universal gas law

PV = nRt

pressure x volume = number of moles of gas x gas constant x temperature

R = 8.314 joules per degree Kelvin
T is absolute temperature (degrees Kelvin)

As temperature increases so does pressure at constant volume....the more gas the higher the pressure (WOW!)....I am guessing that the tire manufacturers are aware of this amazing scientific fact and have taken it into account when publishing cold tire pressure requirements
AND
I bet they have done all sorts of measurements and stres tests on the tires taking into account lots of variables

For me....I check pressure in the AM.....very, very occassionally I have to add some premium 78% nitrogen blend....this has worked for the last 30 or so years of motorcycling

The OP lives in Las Vegas. He ain't gonna see 68 degrees for a few more months. So, I'm sure he just wanted to know how to check his pressure when "cold" is 90 degrees.

 

[jjsC6]

Goodness.....some on this forum really like to worry about things they needn't worry about....nonetheless for the record:

Universal gas law

PV = nRt

pressure x volume = number of moles of gas x gas constant x temperature

R = 8.314 joules per degree Kelvin
T is absolute temperature (degrees Kelvin)

As temperature increases so does pressure at constant volume....the more gas the higher the pressure (WOW!)....I am guessing that the tire manufacturers are aware of this amazing scientific fact and have taken it into account when publishing cold tire pressure requirements
AND
I bet they have done all sorts of measurements and stres tests on the tires taking into account lots of variables

For me....I check pressure in the AM.....very, very occassionally I have to add some premium 78% nitrogen blend....this has worked for the last 30 or so years of motorcycling

But the question is, what pressure do you set it to? Do you set it at the actual pressure the manual tells you, or do you adjust for ambient temperature?

 

[05nwl]

But the question is, what pressure do you set it to? Do you set it at the actual pressure the manual tells you, or do you adjust for ambient temperature?

Adjust for actual ambient cold (before running) temperature . 1 psi per 10 degrees F up or down from 68 degrees F (98 degrees ambient before running = plus three psi over your normal cold psi). Then don't touch it all day.

 

[jjsC6]

Adjust for actual ambient cold (before running) temperature . 1 psi per 10 degrees F up or down from 68 degrees F (98 degrees ambient before running = plus three psi over your normal cold psi). Then don't touch it all day.

I read all that above, I was trying to get his thoughts as he seemed to simplify it so much.

I've been driving for well over 40 years (as have most of us on this forum!). I have never once read an owners manual that told me to adjust for temperature. The entire concept seems awfully strange to me because pressure is pressure in my simple mind (yeah, I'm ready for the shots I'll take for that). I get that heat effects pressure, but isn't pressure the end game? If my trusty tire gauge tells me I have 41 lbs in a tire, why does it matter how it got to 41?

I currently own a BMW motorcycle with a temperature corrected pressure readout from the factory, and I had a Concours 14 that had same. So I'm willing on believing there is something to it. But it sure seems like a bizarre concept to me. I would have to put 45 lbs in my BMW rear tire right now to get the dash readout to show 41. I just am not comfortable putting 45 lbs in my tires when I leave in the morning just to make the readout on my dash happy.

I know what some of you are going to want to say - please understand that I agree it may be the right think to do. That doesn't change the fact that it does not sit well with me.

 

[05nwl]

I read all that above, I was trying to get his thoughts as he seemed to simplify it so much.

I've been driving for well over 40 years (as have most of us on this forum!). I have never once read an owners manual that told me to adjust for temperature. The entire concept seems awfully strange to me because pressure is pressure in my simple mind (yeah, I'm ready for the shots I'll take for that). I get that heat effects pressure, but isn't pressure the end game? If my trusty tire gauge tells me I have 41 lbs in a tire, why does it matter how it got to 41?

I currently own a BMW motorcycle with a temperature corrected pressure readout from the factory, and I had a Concours 14 that had same. So I'm willing on believing there is something to it. But it sure seems like a bizarre concept to me. I would have to put 45 lbs in my BMW rear tire right now to get the dash readout to show 41. I just am not comfortable putting 45 lbs in my tires when I leave in the morning just to make the readout on my dash happy.

I know what some of you are going to want to say - please understand that I agree it may be the right think to do. That doesn't change the fact that it does not sit well with me.

But, that is exactly what you are supposed to do.

From my GL1800 owners manual:
"Always check air pressure when your tires are cold - after the motorcycle has been parked for at least three hours. If you let air out of your warm tires to match the recommended cold pressure the tires will be underinflated." "The recommended "cold" tire pressures are 36 front, 41 rear."

From my cars owners manual:
“Cold tire inflation pressure means: all tires must be cold, ambient temperature maximum 68 degrees F, when adjusting the inflation pressure.”
“When tires are warm, the tire pressure is increased.”
“Never let air out of hot tires. This could cause the tire pressure to fall below the prescribed value.”
“Insufficient tire filling can cause tires to overheat and thus be damaged – even invisibly. Hidden tire damage is not eliminated by subsequently correcting the tire pressure.”

 

[NJREF]

But the question is, what pressure do you set it to? Do you set it at the actual pressure the manual tells you, or do you adjust for ambient temperature?

Nope...COLD = when I start in the AM

All my years of riding I never made any adjustments for "cold" temperatures....and yet I have never had any issues with tires (motorcycles, trucks, tractors, automobiles)

That and I doubt most "pressure gauges" are really not all that accurate....AND...I bet if we did a blind study and changes tire pressure by, say, 1 psi, none could tell the difference....yet some argue over 0.1 psi :shrug:

But what do I know

 

[2Wheeler]

psi

Tire manufacturers calculate their recommended pressure while taking changes in climate/ambient temperatures into account. I put in the maximum amount recommended by the manufacturer and don't think much more about it until I check the pressure again a week or 2 later. Tires seem to last longer at maximum pressure recommended, plus, the tire can lose a pound or 2 below maximum with no damage as long as psi doesn't drop below the recommended minimum pressure. Just my $.02. PS - I do all my checking and inflating before riding the bike. Ride safely, 2W

 

[LarryM]

Tire pressure is an inexact science, and that does not sit well with people who crave order in their lives. If you let yourself get carried away with this issue, it will consume you. I understand it, because I have had my own obsessions at various times in my life. But it is something you have to get a grip on and come up with a happy medium.

As mentioned, most gauges are not all that accurate. And what do you do if it is 50 degrees when you leave in the morning, and 85 later in the day? What about the cooling effect of rain on the road, or the heating effect of the sun on the road as opposed to an overcast day? The possibilities can drive you nuts if you let it.

The answer is, don't worry about it. Tires all have a wide, safe pressure range they can operate in. And unless you are significantly overloading your bike, you will never exceed those safe limits as long as you follow the manufacturer's simple cold pressure guidelines. If you ARE overloading the bike, no amount of pressure monitoring will help. By following the standard cold temperature reading, you will stand the best chance of keeping tire pressure and tire temperature changes during the day to a minimum.

When manufacturers plead with owners to monitor their tire pressure, they aren't worried about a few pounds. They are worried about people that never check their tires, ending up with them significantly underinflated.

Yes, there are charts out there, created by those who are also overly obsessed with tire pressure. Don't let yourself join in their misery and fall into the same trap.

Check your pressure once in awhile before a ride, and just go out and enjoy your bike.

 

[jjsC6]

But, that is exactly what you are supposed to do.

From my GL1800 owners manual:
"Always check air pressure when your tires are cold - after the motorcycle has been parked for at least three hours. If you let air out of your warm tires to match the recommended cold pressure the tires will be underinflated." "The recommended "cold" tire pressures are 36 front, 41 rear."

From my cars owners manual:
“Cold tire inflation pressure means: all tires must be cold, ambient temperature maximum 68 degrees F, when adjusting the inflation pressure.”
“When tires are warm, the tire pressure is increased.”
“Never let air out of hot tires. This could cause the tire pressure to fall below the prescribed value.”
“Insufficient tire filling can cause tires to overheat and thus be damaged – even invisibly. Hidden tire damage is not eliminated by subsequently correcting the tire pressure.”

You sort of addressed my question....I think. But then in your "from my car owners manual" you back tracked. If you quoted the entire car manual (which I believe you did), then it tells you to set the pressure cold at 68 degrees, but it does not tell you what to do if it's not 68 degrees.

Nope...COLD = when I start in the AM

All my years of riding I never made any adjustments for "cold" temperatures....and yet I have never had any issues with tires (motorcycles, trucks, tractors, automobiles)

That and I doubt most "pressure gauges" are really not all that accurate....AND...I bet if we did a blind study and changes tire pressure by, say, 1 psi, none could tell the difference....yet some argue over 0.1 psi :shrug:

But what do I know

I agree that filling them when "cold" in the morning is the correct method. The only thing I was discussing was whether or not you really should use an ambient temperature factor when filling them cold. To try to be as clear as possible, what I mean is that if it's 90 Degrees outside and you want the pressure to be 41, do you really put 44 in them because that is what the correction factor says for 90 degree ambient???

 

[jjsC6]

Tire pressure is an inexact science, and that does not sit well with people who crave order in their lives. If you let yourself get carried away with this issue, it will consume you. I understand it, because I have had my own obsessions at various times in my life. But it is something you have to get a grip on and come up with a happy medium.

As mentioned, most gauges are not all that accurate. And what do you do if it is 50 degrees when you leave in the morning, and 85 later in the day? What about the cooling effect of rain on the road, or the heating effect of the sun on the road as opposed to an overcast day? The possibilities can drive you nuts if you let it.

The answer is, don't worry about it. Tires all have a wide, safe pressure range they can operate in. And unless you are significantly overloading your bike, you will never exceed those safe limits as long as you follow the manufacturer's simple cold pressure guidelines. If you ARE overloading the bike, no amount of pressure monitoring will help. By following the standard cold temperature reading, you will stand the best chance of keeping tire pressure and tire temperature changes during the day to a minimum.

When manufacturers plead with owners to monitor their tire pressure, they aren't worried about a few pounds. They are worried about people that never check their tires, ending up with them significantly underinflated.

Yes, there are charts out there, created by those who are also overly obsessed with tire pressure. Don't let yourself join in their misery and fall into the same trap.

Check your pressure once in awhile before a ride, and just go out and enjoy your bike.

I'm with you.

 

[LarryM]

You sort of addressed my question....I think. But then in your "from my car owners manual" you back tracked. If you quoted the entire car manual (which I believe you did), then it tells you to set the pressure cold at 68 degrees, but it does not tell you what to do if it's not 68 degrees.



I agree that filling them when "cold" in the morning is the correct method. The only thing I was discussing was whether or not you really should use an ambient temperature factor when filling them cold. To try to be as clear as possible, what I mean is that if it's 90 Degrees outside and you want the pressure to be 41, do you really put 44 in them because that is what the correction factor says for 90 degree ambient???

The manual he quoted said maximum 68, not exacly 68. But that is a tough thing to do in many parts of the country, let's say Nevada, where temps may never drop below 80 for many weeks.

Ambient temp is important, but like many things, it is a common sense thing. Tire pressure wil drop drastically when we head into the cold months. You have to add a lot of air to tires to compensate.

But in your example, if I were to leave for a ride at noon, when it is 90, I think it is best to skip checking pressure on that day if you had already checked it recently. Check it the next day first thing in the morning. Don't guess when checking pressure.

 

[05nwl]

The manual he quoted said maximum 68, not exacly 68. But that is a tough thing to do in many parts of the country, let's say Nevada, where temps may never drop below 80 for many weeks.

Ambient temp is important, but like many things, it is a common sense thing. Tire pressure wil drop drastically when we head into the cold months. You have to add a lot of air to tires to compensate.

But in your example, if I were to leave for a ride at noon, when it is 90, I think it is best to skip checking pressure on that day if you had already checked it recently. Check it the next day first thing in the morning. Don't guess when checking pressure.

Skip checking the pressure because the ambient temperature is 90 degrees? Why? This is really simple. The vehicle or tire manufacturer tells you the correct pressure at 68 degrees (cold). Pressure increases and decreases about 1 psi per 10 degrees. If the correct cold pressure is 36 psi at 68 degrees and the ambient is 90, just add 2 psi and it should read 38. If it is less than that add some. If the ambient is 50, it should read 34. How can it be any more simple? And, it is evident from the manuals quoted in my earlier post that the mfgs are way more concerned with under inflation, especially in warm weather, than with over inflation in terms of safety. Makes sense too. An over heated tire (from friction) in hot weather can be a really bad thing. (Damn, my "return" key is not working.)

 

[Road Hog]

What he said.

 

[LarryM]

Skip checking the pressure because the ambient temperature is 90 degrees? Why? This is really simple. The vehicle or tire manufacturer tells you the correct pressure at 68 degrees (cold). Pressure increases and decreases about 1 psi per 10 degrees. If the correct cold pressure is 36 psi at 68 degrees and the ambient is 90, just add 2 psi and it should read 38. If it is less than that add some. If the ambient is 50, it should read 34. How can it be any more simple? And, it is evident from the manuals quoted in my earlier post that the mfgs are way more concerned with under inflation, especially in warm weather, than with over inflation in terms of safety. Makes sense too. An over heated tire (from friction) in hot weather can be a really bad thing. (Damn, my "return" key is not working.)

I don't agree with that assessment at all. Cold pressure isn't rated at a specific temperature. Go read that manual excerpt again. It says "up to" 68 degrees.

I put 32psi in my cars. I put that same pressure in them whether it is 70 degrees or 10 degrees. That is what you are supposed to do. You don't lower the pressure as the ambient temperature drops. No manufacturer would ever suggest that. In fact, most of what I have read says the exact opposite. Up here in the cold winter states, we are often reminded to check our tire pressure when temps drop because tire pressure drops when it gets cold.

Frankly, I don't worry too much about what the ambient temperature is. My comment was mostly hypothetical for those that waste too much brain power contemplating this stuff. I don't think I have ever had a time when I wanted to check tire pressure at 90 degrees. But one psi at 10 degrees over that maximum is meaningless. None of us have a gauge that is that accurate.

Why does everyone look to make simple procedures so complicated? You look at the mfr's recommendations and follow it. There are no adjustments or calculations to make. The only complicated part is that you have to remember to check pressure before you go riding.

 

[05nwl]

I don't agree with that assessment at all. Cold pressure isn't rated at a specific temperature. Go read that manual excerpt again. It says "up to" 68 degrees.

I put 32psi in my cars. I put that same pressure in them whether it is 70 degrees or 10 degrees. That is what you are supposed to do. You don't lower the pressure as the ambient temperature drops. No manufacturer would ever suggest that. In fact, most of what I have read says the exact opposite. Up here in the cold winter states, we are often reminded to check our tire pressure when temps drop because tire pressure drops when it gets cold.

Frankly, I don't worry too much about what the ambient temperature is. My comment was mostly hypothetical for those that waste too much brain power contemplating this stuff. I don't think I have ever had a time when I wanted to check tire pressure at 90 degrees. But one psi at 10 degrees over that maximum is meaningless. None of us have a gauge that is that accurate.

Why does everyone look to make simple procedures so complicated? You look at the mfr's recommendations and follow it. There are no adjustments or calculations to make. The only complicated part is that you have to remember to check pressure before you go riding.

ok, let's try this. Say you're not in Ohio. Say you're in Lake Tahoe (this is a situation I see every summer). You get up early, it's 28 f and check your pressure. It reads 37 and you normal cold set point is 41. So it is actually perfect, but using your method you add 4 psi. Later that same day you are cruising through Ridgecrest, ambient 105f, road surface 160f. You would have lost about 1 psi due to altitude but gained 8 due to ambient alone and another 2-3 due to friction and another 2 -3 due to road surface, so your pressure is somewhere around 53-55 psi. But only 4 of those are because your method was incorrect, so will it cause a problem? I don't know. How good are your tires, how much load are you carrying? If you're on Metzlers you may already be dead.:joke:

And, over inflation is better than under inflation so you may be ok.

 

[LarryM]

If you go to extremes, you can find fault with just about any procedure. If I did, I would adapt. Personally, I have never experienced a 70 degree swing in temps in one day, and don't ever expect to come close. Your example points out that no matter where you live, you will have something that is not seen anywhere else. And each area of the country has ways of dealing with that uniqueness. That is the trouble with a forum that brings together people from all over. Just like dealing with the hot dry conditions of the West is different than the sticky humidity of the Midwest and Southeast.

 

[saltmar14]

several post list the cold tempeture as max 68deg my qustion started because for the last several weeks cold has been 106-110. today i noticed my vans tire warning light on so drop in to tire center to have them fill a low tire, he said they where not low but one was at 44deg and others where from 38-34, i just had them checked and filled 3 weeks ago due to screw in tire. he said they should be 34 yet sitting cold, at 103 this morning pressures where all over, enough to set off warning on dash.

 

[dheaton]

I just use tires that are solid rubber that way I don't worry about the air. :lol:

several post list the cold tempeture as max 68deg my qustion started because for the last several weeks cold has been 106-110. today i noticed my vans tire warning light on so drop in to tire center to have them fill a low tire, he said they where not low but one was at 44deg and others where from 38-34, i just had them checked and filled 3 weeks ago due to screw in tire. he said they should be 34 yet sitting cold, at 103 this morning pressures where all over, enough to set off warning on dash.