New 31++ Portable Air Inflator For Car Tires. The less expensive models are a less difficult buy to make, however, they truly aren't. Most car tire inflators have a maximum allowable psi, which limits the usage of the inflator. The best portable tire inflators can fit into the trunk or cargo area of your vehicle so you'll have easy access to it during a roadside emergency. The compressed air enables you to do the job quickly and efficiently.