VERY interesting device to making filling tires from motorhome tank a breeze.
Air-Pressure Booster (http://www.fmcmagazine.com/motorhome-articles/4064-air-pressure-booster.html)
Good article on this thing I never heard of before.
Hi Barry,
Maybe not so fast to run out and buy it. I have one of these devices that has about a 5" x 12" tank and it takes a long time for it to build up pressure to double whatever you put into it. Therefore it may be a very slow process to fill RV tires. Great idea though.
Jim
I have posted on these devices before if you connect to the motor home's air supply they are incredibly fast and high pressure. It depends on the volume of air in to the booster, the source of air and what the booster is set on. It actually is a doubler on my unit so if set at 100 lbs you get 200lbs of pressure. I can air up from 80lbs to 120 in less than a minute as long as the coach is on high idle and the governor is cycling. In the picture your auxillary pump may have high pressure but limited flow rate. it will work much better of coach air.
I liked that post someone made about how it was better to use the coach air since it was filtered. I'd never thought about it!
It's also dried which is very good
I first saw one at M&G in the owner's coach, when they installed my brake system. Never understood how something so simple couple double anything. Seemed like magic. Was always wishing I could find something like that to double my money.
And let's remember it's also 78% nitrogen as well. Just had to add that, for those like me that can settle for less than 100% nitrogen in our tires.
Nitrogen is for those who were not required to take chemistry OR physics and want to listen to OPINIONS instead of FACTS.
Both DRY air and N2 follow the ideal gas law (PSI change for a given temperature change). Physics is physics.
Only real difference is WET air (like those coin op compressors at convenience stores). No dryers. No big surprise, but WATER does not follow the ideal gas law. Said a different way, more PSI change for a given temperature change.
Brett,
Possible H2O content in air contribute to belt rust over time. The 8 year old Michelin that blew on my LF last year had incredibly rusted steel belts, which I surmise created tire failure
Tim,
Totally agree.
But, if you use your on-coach air system, it is DRY air.
Brett,
My high school chem and physics were before the discovery of nitrogen. However, I seem to remember hearing that the molecular structure of nitrogen is a larger size than oxygen, making it harder to migrate through the structure of the tire. Is this all BS, and I should never had traded the cow for beans? :))
Len
Len,
Hopefully this link will work. It is from some of the material that Mike uses for one of his classes. http://www.getnitrogen.org/pdf/graham.pdf
Pamela & Mike
So, barring a leak, how many lose air in their RV size tires (not smaller tires)?
Over the years, I find that I need to add air once or at most twice a year.
Generally "refill" them during the first cold snap and they are (according to the TPMS) pretty steady through the summer. Then recheck first cold snap. Yes, the warmer temperatures helps offset the very small loss.
Thanks Pam and Mike for the link. I think I got a headache reading it. I had heard about the difference between Nitrogen and "air", but sometimes what you are hearing is hype or misinformation.
My 350Z has a really touchy TPMS that seems to be set off after a cold front (low pressure zone) comes through. This may be dumb, but would the difference between the air pressure on the outside of the tire affect the effusion of the air inside the tire, or is it just the cold air in the tire has less pressure?
Hope I am not messing up this thread.
Thanks,
Len
That article compared nitrogen with oxygen, not nitrogen with air. Physics is still physics.
My experience indicates that barometric pressure has a negligible effect on tire pressure. Ambient temperature has a large effect on tire pressure.
Try this little experiment. In the morning (before sunrise), set the pressure in the tires on a vehicle (car, truck, RV) to a pressure appropriate for the tire and vehicle. Check the pressure in the afternoon after the ambient temperature has reached the high for the day. You will see a significant rise in the pressure that you measure.
If you can, park the vehicle so that the afternoon sun shines on one side of the vehicle, while the other side is in the shade. You will probably find that the tires with direct sunlight shining on them will have higher pressures than the tires in the shade.
Also, measure tire pressures in "cold" tires, vs. "hot" tires. "Cold" means that the tires are at ambient temperatures and the vehicle hasn't been driven for several hours. It's easy to see these changes with a TPMS that provides pressure readings for each tire.
"Recommended pressures" apply to "cold" tires.
It's nearly 18 months between having to add air to my 275X80RX22.5 tires. And that's with Pressure Pro's on all tires. I consider myself fortunate. As Brett says, most often it will be just as wiinter begins to set in.
Just a couple of points to add to the discussion:
- Air - the stuff you will get from any air pump that is not fed a special diet is already 78% molecular Nitrogen (N2)
- The process of oxidation is well-named. We are all familiar with 2 common forms of oxidation - rust and fire. The common active agent in an oxidation reaction is oxygen. The degradation that occurs to substances exposed to the atmosphere - apart from damage caused directly by UV light - is mostly the result of oxidation. That includes the degradation of rubber. So any time you can eliminate oxygen (and water) you will also reduce or eliminate oxidation.
So getting rid of moisture from the gas you put in your tire is definitely a good thing. Getting rid of the oxygen is also a good thing. Since the atmosphere is only 21% oxygen, how much difference it makes as a practical matter, I don't know (sorry).
Air Composition (https://eo.ucar.edu/basics/wx_1_b_1.html)