Watch the elevation

[Tom]

When we went to bed last night I realized I'd forgotten to let air out of the air bags. Sure enough, they were inflated like a bag of potato chips at 30,000 feet. This is usually one item on my checklist if we'll be driving to or through high elevations, but I had forgotten this time. Hopefully it didn't do any permanent damage to the seams. A friend of ours had to replace their air bags for that reason.

Before leaving this morning I figured I'd check tire pressures, and was expecting them to be higher than at sea level. But they were within 1lb or so of where they were before we left home. OTOH it was only 50+ degrees up here. So, did the reduced volume due to lower temperature cancel out the increase in pressure due to altitude?

BTW thanks to an idea from a friend of mine, I bought an IR thermometer. Now, instead of running my hand over all tires on the coach and toad every time we stop, I just point and click.

 

[Ned]

If you did open a seam, you'll know it real soon

I've used an IR thermometer for several years to check my tires at rest stops.  After a few tests, you'll know what's normal for your tires.  The sunny side will be warmer than the shaded side and the inside duals run hotter than the outside.  Usually all tires are within 10-20F of each other.

 

[Ron]

I also use an IR thermometer to check tires while traveling.  I was at a flying J refueling one time and was doing my usual walk around and  thermometer soon as he finished his run.

 

[Smoky]

OK Naive question here... what conclusions do you draw from thermometer readings on the tires?

And also, when you are traveling into higher elevations, how do you check and adjust airbag pressure?  Do you have to stop to do this?

I have also wondered about tires.  When pulling my trailer I knew my tires were supposed to be at 50 psi, on both truck and trailer.  But I was never sure if they were supposed to be readjusted with elevation changes.  All this is likely old hat for the oldtimers here, but I would greatly appreciate a fuller discussion on air pressure vs. elevation.

 

[BernieD]

When we went to bed last night I realized I'd forgotten to let air out of the air bags. Sure enough, they were inflated like a bag of potato chips at 30,000 feet. This is usually one item on my checklist if we'll be driving to or through high elevations, but I had forgotten this time. Hopefully it didn't do any permanent damage to the seams. A friend of ours had to replace their air bags for that reason.
[/unquote]

Tom

Your airbags should be self adjusting, if they get to hard, the ride height adjuster should let some air out to lower the bags.

BTW thanks to an idea from a friend of mine, I bought an IR thermometer. Now, instead of running my hand over all tires on the coach and toad every time we stop, I just point and click.

Be even easier if you had the PressurePro ;D ;D ;D

 

[Tom]

Be even easier if you had the PressurePro

Very true Bernie. I'm just having sticker shock at this time, but one of these days I'll probably spring for a PP or equivalent.

 

[Tom]

OK Naive question here... what conclusions do you draw from thermometer readings on the tires?

None yet Smoky. I'm still in a data collection mode. But, as someone else suggested, a large difference in tire temperatures might suggest something like low air pressure on that tire.

And also, when you are traveling into higher elevations, how do you check and adjust airbag pressure?

I'm not aware that I can check or adjust air bag pressure on the coach. I was referring to the air bags in our bed.

I would greatly appreciate a fuller discussion on air pressure vs. elevation.

LOL we had one of those in the old location. But it doesn't hurt to have it again.

 

[Tom]

If you did open a seam, you'll know it real soon

I figured I would.

 

[Carl L]

I have also wondered about tires. ?When pulling my trailer I knew my tires were supposed to be at 50 psi, on both truck and trailer. ?But I was never sure if they were supposed to be readjusted with elevation changes. ?All this is likely old hat for the oldtimers here, but I would greatly appreciate a fuller discussion on air pressure vs. elevation.

In terms of tire pressure, elevation is trival. ? Normal air pressure at 20?C at sea level is 14.7 psi. ? ?At 500 meters (1640 ft) ?it is ?13.8 psi. ? At 2000 meters (6562 ft) it is 11.9 psi. ? That is 2.8 psi difference. ? On a 50 psi cold inflation pressure that ain't a whole lot. ? Moving the temperature of a tire from 20?C to 50?C will raise the pressure some 5.3 psi. ?That is the sort of change you get in normal driving and the reason why tire mfrs. insist that you measure inflation cold, and warn against lowering inflation on a hot tire.

 

[Tom]

Thanks Carl for that concise response.

 

[Smoky]

LOL tom, I thought you were talking about COACH chassis airbags.? I was beginning to think I had a new learning curve ahead of me.

 

[Carl L]

Thanks Carl for that concise response.

Concise but wrong. :'(  The real numbers have been edited in.  It has been a few years since Physics 101 and the gas laws.

 

[DougJ]

And Carl, did you use a real gas or an ideal gas for those calculations

Doug

 

[Karl]

Don't worry Carl; they won't send you to jail for breaking gas laws

 

[Carl L]

And Carl, did you use a real gas or an ideal gas for those calculations

Doug

 

Better yet, a complete gas. ;D

 

[Carl L]

Don't worry Carl; they won't send you to jail for breaking gas laws

Like the old bumper sticker said

? ? ? ? ?Remember -- 186,000 miles per second.? ?It's the law!

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ;D

 

[Tom]

they won't send you to jail for breaking gas

eh? I sure hope not.

 

[DougJ]

they won't send you to jail for breaking gas

eh? I sure hope not.

No, but watch out if you break wind ???

Doug