i use one of the cheap compressors from harbor freight for the last year and a half and actually it does very well for what it is. i timed it yesterday and to air up my 35 12.5 15's from 10psi to 30psi it took 3minutes and 22seconds a tire. id say less than 15 minutes to fill up 4 fairly large tires is respectible. that said i am already set up for co2(just have to fill the tank) and will start using that as my primary air, but i will definelty keep my compressor as a backup and will still probably use it when time isnt a factor at all just cause its free to use(other than the gas when the trucks idiling)