I'm new to airbags (experience wise) but I fully understand operation, pumps, tanks, valves, etc.  It's the daily use, how long to pump up, which bags are better, etc etc.  I only know one guy personally that has them but he has a pretty standard setup.

How low does your tank pressure actually get?  I know that switches turn on 110psi-ish, shut off at....whatever...here's why I ask.

I have a 64 Olds Starfire that's fixed up pretty clean and want to get bags.  I recently coverted the front from drum to disc brakes and the 14" spare tire won't fit anymore, so I thought what if I replaced it with a HD rim tire (say for trailers) that can go up to 90 psi and use it as a sub tank.  I would put a pancake tank in the middle of it to use for higher pressure use.  But when that tank dropped below 90 psi, the tire would drain to equalize pressure, only to then be replenished by the pumps.  The input to the tire would have a regulator, and the output a check valve.  All this to save space and of course to be different.

I see people talking about how it takes a couple minutes to refresh their tanks but thats from when it shuts off (110 psi) to full (145-200).  But how low was the tank getting really?  My understanding is that bags should operate at 45-60 psi, so anything over that should fill them. 

Ok just to recap...I do not want to use a regular car tire. I know it will bust at these high pressures.  I've already been slammed on another car forum, but no one seems to have had a substantial argument about the whole idea.  I want to save trunk space.  It doesn't have as much as you think. It's a driver and after putting in a car cover, luggage, cleaning stuff, some basic tools..it gets crowded really quick.

Don't mind the details of lines, valves, etc, just need feedback if 90psi (or even a pinch higher) in a sub tank would even do me any good.
thanks

Your operating pressure can be deceiving I hava a 97 dakota with 7.5 inch bags all around for the rear it takes about 48 psi to lift but for the front it's closer to 95 all this with a 4 banger under the hood. Alot less weight than your setup. My tank is a 3 gallon hand made setup to fit within the frame rails and it's not unheard of for it to be as low has 30 psi... Hope this helps.

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