Perhaps of our ubiquitous rain, I got tired of hooking up my Viair 400P directly to the battery and decided to go with onboard air with ARB CKMA12. What I am trying to figure out now is the the size of the air tank required so I can fill all four in a minimum time. It has been way too many years since my university days, so I am having trouble with calculations.

Here my specs:

- tire size: currently 33" (285/75R16), but I want this to work for 35" (315/75R16)
- required fill pressure: from 10 to 15 PSI
- max compressor pressure: 100 psi (although it seems that it's possible to get it to 180 psi by overriding a safety valve)

By my calculations, a 33" tire is supposed to have around 118 L volume. Where I got stumped is how to use this information to figure out volume of air at the needed pressures, and the required tank size.

Any help? If you know how to figure this out, would appreciate if you could at least briefly set out the formula you used.

TIA