I currently own a makita 12v cxt air compressor (MP100DZ). Wondering how long your harbor freight 12v takes to fill your tires. I've never worried about the makita filling car tires, but with a 50% duty cycle (5min on 5min off) and 315/70s sounding like a lot of air I'm not sure how many 4.0ah batteries and how much time I would need to get off the beach. Curious on your harbor freight experience because it seems to have a low cfm rating like mine.Im cheap and have one of these. Works great on my other vehicles. Why spend $400 on a ARB?