Tire pressure is a cold tire wherever you are,(ie.. Canada or Texas) NO formula needed.

 

Tire pressure is a cold tire wherever you are,(ie.. Canada or Texas) NO formula needed.

Muddog,
I may be remiss in my evaluation of your answer to FINTUBE. I believe he was looking for a more scientific expose' . If you could make a clearer delineation of the formulation that he arrived at, I believe we all would be happier with the conclusion. I believe the "line of demarcation":22yikes: has been broached and needs to be clarified. Thanks. opcorn:opcorn:opcorn: Semper-fi Mike

 

The variables in the forumla I use to calculate appropriate "cold inflation" pressure (41 front and 42 rear) stipulate an assumption that "t" (temperature) is 72F and "a" (altitude) is 880' relative to standard sea level. Thus any variation(s), either singularly or in tandem, about these assumed ambients within the tolterable limits of human survival won't matter worth a ratz ars (technical term for doodly squat). That thar is da way I figgers it.

prs

 

hehehe This is going to get interesting....

On a serious note, it is fair to say that there is a 10:1 ratio on temp vs pressure.

With that understanding, could we not calculate a ratio for altitude as well? For every 1,ooo feet, you have XX change in tire pressure, as an example.

 

Where I was going with this thread was, there has/is a lot of talk about tire pressure. I was looking for some input on this subject from others that my have some experience on the matter. Heck, there may even be some other person that is new to the Goldwing that never thought about this and it may have some merit. There has been various discussions about tire pressure and what the results are from improperly inflated tires. Do you adjust you tire pressure every morning while on a trip? Should you?
I have never taken a long trip on a motorcycle until recently, and noticed the difference in tire pressure on my recent trip. I asked a number of riders I met along the way and not one of them had checked their tire pressure since they left home. Maybe it is not a concern. There is an influence on tire pressure with both temperature and altitude. I don't check my oil level between changes because I don't see oil under the bike when parked or smoke from the exaust while running, therefore I made the assumption that it should not be using oil. I cannot look at the tires and tell if they are properly inflated only if they are extremely low or flat.
If "new winger a" starts out on a trip from Texas and had read on the board that some guy in Montana that has 8317 post says that 40/42 is the best tire pressure so that is what I will run. But he didn't get the part that temperature and altitude has an effect and he doesn't need to check his tires along the way, then didn't we fail as a board and group that others look to for information.
Not all of us have a PhD from MIT and some use this board for discussion and benefit from the experience of others. I don't want to ride the Dragon 136 times in 9 minutes or fully dissamble and reassemble my wing in a half hour. :bow:I do enjoy my vehice and have benefited from some on this board.
Just trying to get some feedback from some that may know and bring some useful information to the group.
Doug

 

Then I submit a serious answer (this may be tought for me).

No. I do not adjust my tire pressure on every pre-ride, nor should I unless there is a slow leak and I have been unable to repair that. However, I am among the very rare group of riders that does a pre-ride every day and I do check the pressure as part of that.

If in the East US and I ride to North Carolina to ascend Mt. Mitchell or to New Hampshire to ascend Mt. Washington, I DO NOT stop and let air out; nor do I add any prior to decending same. Nor would I for Pike's Peak, even if beginning in Death Valley; its just not that big of a deal in the short term.

Now, if a certain tire rides best for me at 41#front and 43#rear while I am residing on Long Island; would I be differently served by that same pressure use if I moved to Denver? NO again, even in the long term of things this would be relative to the prevailing ambient conditions. My Long Island tires would have a few more molecules of air in them to get that pressure than would my Denver tires, but so does the ambient atmosphere there. So your Texas Pardner can adopt his Montana friend's pressures and enjoy the same relative performance.

BTW you really should check your oil; hill or dale.

prs

 

I post my experience since I just returned from 6 weeks across the US and back. YES, I had to adjust my tire pressure with the altitude change. I ride a trike where at 600' ABL (above sea level), I put in 41 front, 23 rear cold tire pressure. I do a pre-ride every day before starting but didn't adjust tire pressure until I saw about 45 front and 26 rear. Altitude? I don't know, it was in Wyoming. Then everyday as the altitude changed I adjusted the pressure, adding or removing as the altitude changed. Temps in the morning were average 50 /60 range so may have some influence but the major difference I saw was the altitude changes. Eigth thousand miles and now back home with tires that have 17,500 on them since new (front and rear) and they still run true (no cupping on front). Worked for me, your experience might vary.

 

....Knowing this, do we need to calculate/adjust our tire pressure to the conditions as we check them before the ride?....

This is a subject that can get complicated quick. Here's the easy scoop:

Let's start by assuming that you like to keep 41 "psi" in your rear tire.

Notice that I put "psi" in quotes....there are two pertinent ways to define pressure in a closed vessel (like a tire). Let's just say we are talking about the psi reading we will see on our tire gauge (what the smart guys would call "psig," or "psi gauge" - this is the pressure in the tire compared to the air surrounding the tire).

The other way to measure pressure is referred to as "psia," or "psi absolute." This would be the pressure in the tire compared to a vacuum. (Space Shuttle pilots care about both psig and psia, motorcycle riders care only about psig.)

WITH REGARDS TO TEMPERATURE: There is some magic temperature at which your tire should read 41 psi. I don't know for sure what this temperature is, but I do know this: If you've just gotten off the bike after a 200 mile blast down the slab when it's 110 degrees F out and you're 2-up, you should have more than 41 psi in the tire. If you go out to the bike in the middle of the night and it's -5 degrees F in the shed, you should have less than 41 psi in the tire.

I'm lazy and usually check my tire pressures only twice a week or so on a road trip. I check them in the morning before the first ride of the day. No matter what the air temperature is outside, I won't accept anything less than 41 psi. I also won't accept anything more than 43 psi. Then, I'm fat, dumb, and happy, unless I'll be going up in altitude for the next few days, in which case I'll bleed the tire down to 41 psi (if it was higher than this). Likewise, if the pressure is 41 psi and I'll be going down in altitude for the next few days, I'll pump the tire up to about 43 psi.

WITH REGARDS TO ALTITUDE: No matter what the altitude, I follow the same rules as I do with temperature. My tire doesn't care about altitude, it just wants to have an internal psi that is 41-43 greater than the psi of the air around it.

The only part altitude plays in this whole dick-dance is in whether you will be going up or down for the next few days. If you will be staying at roughly the same altitude for the next few days, then your altitude when you are checking your tires plays absolutely no role in your determination of what reading you want to see on your tire gauge.

Clear as mud?

 

And another way to say this:

ELEVATION
If you are at sea level (14.7psi) and there is "no air" in the tire, your guage will read 0 psig. Assume it is just "empty", then if you took this tire still sealed to 10,000 feet (10.1) the guage would read about 5 psig, actually 4.6 but 5 is close enough. So a "rough" estimate for change in elevation is about 1/2 psi per 1,000 feet.

Go up a thousand feet and the pressure in the tire increases by 1/2 psi, go down a thousand feet and the pressure decreases by 1/2 psi. Now figure out how much change in tire pressure makes a difference to you in tire pressure and make an adjustment when your elevation changes to make that kind of difference.

TEMPERATURE
Measuring the tire pressure cold actually means set the pressure when the tire is the coldest it will be during the period of use. As it heats up it will then stay within the tolerences prescribed by the vehicle. The rule of thumb is 1 psi for each 10 degrees of change.

I have seen folks check their pressure after traveling a while. Generally the pressure will be higher. I have a smart tire system and have seen my back tire reach 171 deg F. At that temp a 41 psig tire pressure set at 65 would be about 52 psig. Of course you don't want to let air out to bring it back down to 41 psig because it would be signficantly low when the tire eventually cooled.

 

AlKnowing this, do we need to calculate/adjust our tire pressure to the conditions as we check them before the ride?

Handheld tire pressure gauges are differential pressure gauges. The air pressure in the tires is pressing out against the ambient pressure pushing in. When you inflate your tires to 42psi at sea level, the pressure is 42 lbs/sq in over ambient. Or about 57 psi absolute.

If you go up into the Rockies, say Loveland Pass, about 12,000 ft above sea level, the ambient pressure is about 6 psi less. If you filled your tires to 42 psi at sea level and rode up there, your pressure gauge would read about 48 psi (cold), your tires will be about 6 lbs over inflated. That might be too much and might be a good idea to bleed off some pressure.

So if you bleed off the excess so the tire pressure is back to 42 psi and descend back down to sea level, the differential pressure will be 36 psi, your tires may underinflated, possibly dangerously so. So they will need to be checked and air added.

Kind of extreme example, to be sure.I don't think I would worry much about a short ride into a 2,000 - 3,000 foot higher elevation area. More than that tho, I would give the tire pressure a look-at. Especially given how critical tire pressures are to motorcycle safety.

 

You guys make this too difficult. :joke::joke: Just check the cold tire pressure every morning where you are , that is all there is too it. I normally put two pounds over at the start of a trip, as you do loose about .5 each time you check a tire.

So going on a long trip, front tire calls for 36.....put 38 in it and you have a couple days of air to check the tires...till you have to hunt up a air hose, close while still cold.......or dig out your compessor.....

Go up in the mountains.....short trip, do not worry about it.....going to ride high elevation for several days......check the tires up there......come back down.....next day when cold......check them again......

I never change my crush washer either........:lol:

Kit

 

You guys make this too difficult. :joke::joke: Just check the cold tire pressure every morning where you are , that is all there is too it......

Kit,

In most cases, you would be correct.

However, you should have an idea of environmental conditions expected a few days or so down the road.

For instance, you are in Leadville, CO, during a hot spell and measure your tire pressure before you leave. You like to keep your rear tire at 41 psi and, sure enough, your gauge reads 41 psi. You mount the bike and blast off for Omaha, NE, which has been experiencing unseasonably cool weather as of late.

You arrive in Omaha that evening, rest, and leave the next AM for Chicago.....

Had you bothered to check your rear tire pressure in Omaha that morning, you would have noticed that you are down to 35 psi....not good!

If it had been me, I'd have left Leadville with 44 psi and checked the tire pressure again the following AM in Omaha.

 

Interesting discussion. On the practical side, I have 4 tire gauges none of which read within a pound of each other. How do you know if your gauge is accurate enough to worry about a couple pounds air pressure one way or the other?