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It sounds like a leak in the line like Hoble mentioned. If it was the bag, I doubt it would hold any pressure.


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When I worked at Firestone, I tested these Airlift helper springs under all kinds of temperature and load conditions. If the unit itself failed, the air loss was pretty much instantaneous. Slow leaks were always in the air line, its attachments, or elsewhere.
 

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be mindful of that tongue weight, those bumper bolts aren't the most robust.
I'd worry more about what the bolts are attached to than the bolts themselves. Any flat metal structure is prone to develop fatigue cracks over time due to repeated oscillating loads on the hitch going over bumps and curved freeway slabs. I have had that happen to me...and the hitch was rated way over the load and tongue weight I was towing.
 

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1. What/how do you recommend?
Remove rear bumper and body clips as in the e-trailer?
2. Take pictures of mounting area metal?
3. What additional reinforcement or alternative connection to frame/unibody do you suggest?
(Dd you reference "the other one" - not sure what other pne - do you mean the German factory option westphalian hitch?)
4. Other tips? I'll hold off on my next "heavy test on cargo rack on hitch on rough roads" until I hear more
I don't have specific recommendations, but here was my scenario:

On a '74 Chevy 1-ton van I installed a class-2 hitch for towing an open light trailer with a small formula car. In a relatively short time span, the sheet metal it was mounted to fatigued and failed, allowing the rear end of the hitch to drag on the ground. I contacted the MFG, and they sent me, as a sign of good will, a class-3 hitch that mounted to and through the "frame", which was made from somewhat thicker formed sheet metal.

After several years of use with a much heavier enclosed trailer, but still well within the advertised capacity of the hitch, the frame and the floor panel it was bolted began to show fatigue cracks. I reinforced the cracked areas with 1/4"-thick steel plates. That solved the issue.

So one has to be very careful to monitor the hitch and attachment point condition to prevent or correct issues.
 

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I have noticed my bags gain pressure after driving in the summer, not sure if exhaust or hot pavement, but it went from 20psi at the beginning of the trip to 30 PSI after a couple hundred miles in 80F sunny temps, so be careful with over inflating.
Could also be condensed moisture in the bags evaporating (gaseous H2O is 1700 times the volume of liquid H2O) as they get warm. That will cause a larger than expected pressure gain. Same reason dry air or N2 is recommended for tires.

I use desiccated (dried) air for tires. And the trick for race tires if they were not initially inflated with N2 or dry air is to get them warmed up so the moisture evaporates, and then deflate and refill a few times with N2 or dry air. That usually gets the moisture content down to a dew-point where it won't condense and cause issues. You can do the same for the airlifts.
 

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Thanks Dave, forgive my total noob question but where does an average non-race guy get "dessicated air"?
If you have a compressor, or any other air source, you can buy a small filter-like unit from a variety of industrial-supply places that has desiccant in it. You pass the air through the desiccant and it removes almost all of the moisture. The desiccant can be dried out when you've used it to its limit by baking it for 45 minutes or so at 350F. McMaster-Carr, Grainger, etc. will have them.

Otherwise, you can use N2 or get an air tank and fill it at a shop that has dry air.

What I do at the race track when there is no dry air available is to fill an air tank (or the tires directly) from the track's compressor using the desiccant dryer with an air chuck on it at the end of their air line.
 
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