Author Topic: spare tire as air tank  (Read 6127 times)

Offline chicomecha

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spare tire as air tank
« on: March 27, 2007, 08:41:14 AM »
I know some of you have used your spare tire as a low pressure air tank, but wondered what plumbing you used to make it happen.  Did you just come up with a custom thing to go on the valve stem, or is there something I can just buy?
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Offline Pantheus

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Re: spare tire as air tank
« Reply #1 on: March 27, 2007, 09:03:05 AM »
When I used to do this, I just made an "equalizer" hose.  Standard fittings on both ends, one on the spare, the other on the low tire.  After connected, let them "equalize".  The closed type of fitting works best,  that is only lets air through when both are attached, as opposed to the open type.  Several tires could be "equalized" by balancing those too full with those needing air.

A trap, though, is that we used to run up to 100 pounds of air in the spare, so there was plenty to equalize more than one low tire.  It worked,  but after time the spare became "bloated / fat" , wider in the sidewall area.  I don't think lower spare pressures cause it as much, or as fast.

The next step in the evolution of airing back up was the EngineAir.   A device which replaced a spark plug while pumping air to the tires.   Maybe not a bad emergency "tool" even today, if an OBA should fail,  and you are at 4 p.s.i.,  like I run in the snow.  Of course with CO2 onboard that is less likely.

I guess these admissions also means that I've been wheeling too long. 

Ken
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Offline Sar 450

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Re: spare tire as air tank
« Reply #2 on: March 27, 2007, 10:04:11 AM »
A old guy gave me one of those EngineAir,it was the coolest thing I had seen in a long time. :D

Offline chicomecha

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Re: spare tire as air tank
« Reply #3 on: March 27, 2007, 12:18:23 PM »
I was thinking about this for a trip to Baja, where I have my motorhome towing the Jeep.  The spare for the MH takes up to 90 psi, and I was thinking it could be a handy big air tank to run air tools if I plumbed it right.  I don't think I would be brave enough to try hi-pressure on a Jeep tire.

Pantheus, not sure what you mean about the "closed" type.  do you mean a hose with each end having one of those fillers that lock around the valve stem, with a T between them somewhere that can plug into the air compressor?  If so, would you get enough CFM around the valve stem to run a small air tool?  I was thinking you might have to take out the stem, which makes the hookup harder.
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Offline Pantheus

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Re: spare tire as air tank
« Reply #4 on: March 27, 2007, 12:41:41 PM »
I was thinking about this for a trip to Baja, where I have my motorhome towing the Jeep.  The spare for the MH takes up to 90 psi, and I was thinking it could be a handy big air tank to run air tools if I plumbed it right.  I don't think I would be brave enough to try hi-pressure on a Jeep tire.

I'm not sure I'd "plumb" it,  but instead make a (closed) chuck to female quick disconnect hose,  and try it.  Interesting  to "measure" the CFM, to see how much is generated.  Air tools need CFM, more than p.s.i.   Having your shop compressor near would be handy, to refill (and test and retest).

If the MH normally holds 90 p.s.i.,  I'd think it could tolerate 150 p.s.i. too.

I can assure you that 33 x 12.5 x 15 tires can "hold" 100 p.s.i.  I have one in my "pile"  that did just that for years.


Pantheus, not sure what you mean about the "closed" type.  do you mean a hose with each end having one of those fillers that lock around the valve stem, with a T between them somewhere that can plug into the air compressor?  If so, would you get enough CFM around the valve stem to run a small air tool?  I was thinking you might have to take out the stem, which makes the hookup harder.

Actually,  there are two types of those chucks "that lock onto the valve stem"  Open chuck, closed chuck.

http://www.sunperformance.com/html/products/air_accessories.html 

and almost everywhere else they are sold.  One needs to be cautious that unless there is a large air tank behind a chuck it should be a closed type.

I've never removed a valve stem to air up or down, (although I recognize it may be faster to do so - I'm all too concerned I'd lose it in the mud or snow), and therefore have to carry many spares, or be dead-in -the water/snow.

Ken
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Offline chicomecha

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Re: spare tire as air tank
« Reply #5 on: March 17, 2008, 08:40:54 AM »
So here is what I did in the end.  I made this air dongle:


And after putting 50 psi in the spare, I use this setup to pull enough air from my spare to get each tire from 5 psi (snow), to about 12 psi, which is drivable at slow highway speeds.

Cost about $20 for the parts, some of which you may have laying around already.  MJB welding made the 1 ft air line out of 1/4" rubber line.  You could save a bit of money and just connect the flex line without the quickconnects.  The key is the silver quickcoupler that pushes onto the valve stem.  In Chico, you can find them at Valley Wide Fastener.
"If you're lucky enough to be in the mountains, you're lucky enough."
N6RCJ