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chippy
Super Nomad
Posts: 1722
Registered: 2-2-2010
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With this- https://www.alltopusa.com/collections/air-compressor/product...
and this- https://ezflate.com/products/ez-flate-hyperflex
I can inflate all four e rated tires (Toyo Open Country RT/Trail 255/80r17) from 18psi to 35psi in about 7 minutes.
Deflate in a couple of minutes.
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Udo
Elite Nomad
Posts: 6346
Registered: 4-26-2008
Location: Black Hills, SD/Ensenada/San Felipe
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Mood: TEQUILA!
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Hey, David...Mil gracias for the compressor time ratings. I AM HAPPY THAT YOU TOOK THE TIME TO MEASURE IT.
rquote=1266622&tid=99920&author=David K] Quote: Originally posted by PaulW  | | Quote: Originally posted by pacificobob | The one specification missing from many underperforming compressors
Is CFM@ a given psi. Eg: 60psi. 90psi. [/rquote]
== =
The industry standard is to measure an quote the cfm at free flow.
CFM at a given pressure is meaningless unless the volume the flow is pushing into is defined. Some do it by specifying a tire size.
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It would be great if the Nomads with various compressors also posted the actual time it takes to inflate their tires in real time.
With 16" truck tires (Tacoma, etc.)...
I measured the Coleman brand pump that plugs into a cigarette lighter: 2 psi per minute.
The next two, clip directly to the battery terminals:
Harbor Freight pump: 6 psi per minute (but melted fuse holder)
MV-50: 5 psi per minute.
For sand, I lower to an average of 15 psi (12-18) based on tire type, sand type, and the humidity. My current tires' street pressure is 34 psi.
3-ply sidewall tires need to go to 10 psi to float where 'cheaper' tires only need to drop to 15-18 psi.
To go from 15 psi to 34 psi (19psi added):
Harbor freight: just over 3 minutes per tire
MV-50: almost 4 minutes per tire
Coleman cig. lighter: almost 10 minutes per tire |
Udo
Youth is wasted on the young!
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4x4abc
Ultra Nomad
Posts: 4289
Registered: 4-24-2009
Location: La Paz, BCS
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| Quote: Originally posted by David K |
To go from 15 psi to 34 psi (19psi added):
Harbor freight: just over 3 minutes per tire
MV-50: almost 4 minutes per tire
Coleman cig. lighter: almost 10 minutes per tire |
what is your tire size David?
with that I can give you the volume of air in the tire
only with that we can start comparing
Harald Pietschmann
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David K
Honored Nomad
Posts: 64842
Registered: 8-30-2002
Location: San Diego County
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| Quote: Originally posted by 4x4abc | | Quote: Originally posted by David K |
To go from 15 psi to 34 psi (19psi added):
Harbor freight: just over 3 minutes per tire
MV-50: almost 4 minutes per tire
Coleman cig. lighter: almost 10 minutes per tire |
what is your tire size David?
with that I can give you the volume of air in the tire
only with that we can start comparing |
Just look up, in this thread:
| Quote: Originally posted by David K | | The photo I posted (of the box image) is in your link, so yes.. the same one. Mine inflates my 265/75-16" Tacoma tires at the rate of 5 psi per minute
(going from 15 to 30 psi, in 3 minutes). |
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pacificobob
Super Nomad
Posts: 2306
Registered: 4-23-2006
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| Quote: Originally posted by PaulW |
== =
The industry standard is to measure an quote the cfm at free flow.
CFM at a given pressure is meaningless unless the volume the flow is pushing into is defined. Some do it by specifying a tire size.
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Physics
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4x4abc
Ultra Nomad
Posts: 4289
Registered: 4-24-2009
Location: La Paz, BCS
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all I can find are complicated formulas for tire volume
no go
even if I used a simplified formula I only get the nominal volume
nobody has been able to tell me yet how many times I have to force the nominal volume into the tire to reach a certain pressure
Harald Pietschmann
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Maderita
Senior Nomad
Posts: 667
Registered: 12-14-2008
Location: San Diego
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| Quote: Originally posted by 4x4abc | all I can find are complicated formulas for tire volume
no go
even if I used a simplified formula I only get the nominal volume
nobody has been able to tell me yet how many times I have to force the nominal volume into the tire to reach a certain pressure
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Here's a link to charts for the volume of tires by their size:
https://tireplay.com/tire-weight-by-size-with-volume/
The values are in metric (cubic meters), so that will need converting to cubic feet.
https://www.metric-conversions.org/volume/cubic-meters-to-cu...
Add another volume of that amount for every 14.7 psi of increased pressure.
1 atm = 14.7 psi; 2 atm = 29.4 psi; 3 atm = 44.1 psi, 4 atm = 58.8 psi
For ease, use the following converter. example, 35 psi = 2.386 atm
https://www.checkyourmath.com/convert/pressure/psi_atmospher...
If you'd rather do the math: for psi to atm, multiply by 0.068046
I chose a common SUV/light truck size, 265/75R16
The chart shows 0.17 cubic meters. Converted to cubic feet = 6.0035
At 35 psi, the volume of that tire is 6.0035 x 2.386 = 14.4 cubic feet
There are so many variables when it comes to filling tires, that this info may not be of much value. The atm measurement is based on sea level at 0
degrees C. (32 F.) The output of 12v compressors slows as the pressure backpressure increases. 12v compressors have varying air output depending upon
input voltage. A compressor is significantly faster and more powerful with the engine running (13 volts to 14v), vs. engine off and the battery at
12.2v to 12.6v. Even the shape of the wheel, across bead surface to bead surface must play a role in the total volume.
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4x4abc
Ultra Nomad
Posts: 4289
Registered: 4-24-2009
Location: La Paz, BCS
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Mood: happy - always
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| Quote: Originally posted by Maderita | | Quote: Originally posted by 4x4abc | all I can find are complicated formulas for tire volume
no go
even if I used a simplified formula I only get the nominal volume
nobody has been able to tell me yet how many times I have to force the nominal volume into the tire to reach a certain pressure
|
Here's a link to charts for the volume of tires by their size:
https://tireplay.com/tire-weight-by-size-with-volume/
The values are in metric (cubic meters), so that will need converting to cubic feet.
https://www.metric-conversions.org/volume/cubic-meters-to-cu...
Add another volume of that amount for every 14.7 psi of increased pressure.
1 atm = 14.7 psi; 2 atm = 29.4 psi; 3 atm = 44.1 psi, 4 atm = 58.8 psi
For ease, use the following converter. example, 35 psi = 2.386 atm
https://www.checkyourmath.com/convert/pressure/psi_atmospher...
If you'd rather do the math: for psi to atm, multiply by 0.068046
I chose a common SUV/light truck size, 265/75R16
The chart shows 0.17 cubic meters. Converted to cubic feet = 6.0035
At 35 psi, the volume of that tire is 6.0035 x 2.386 = 14.4 cubic feet
There are so many variables when it comes to filling tires, that this info may not be of much value. The atm measurement is based on sea level at 0
degrees C. (32 F.) The output of 12v compressors slows as the pressure backpressure increases. 12v compressors have varying air output depending upon
input voltage. A compressor is significantly faster and more powerful with the engine running (13 volts to 14v), vs. engine off and the battery at
12.2v to 12.6v. Even the shape of the wheel, across bead surface to bead surface must play a role in the total volume.
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best info in years!
Thank you!
Harald Pietschmann
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Maderita
Senior Nomad
Posts: 667
Registered: 12-14-2008
Location: San Diego
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de nada Harald.
I'm no math whiz, and I had to dig into my memory from Scuba classes 54 years ago!
Btw, 1 atmosphere / 14.7 psi = 33' of water
A typical 80 cu.ft. Scuba tank will fill 5 of those same tires from 0 to 35 psi.
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