Once your trip into the backcountry is over you need to return your tires to street pressure. Failing to do this before you drive very far or drive at highway speeds can cause damage to your tires from overheating or can result in pulling the tire off the rim. Here are a few of the most popular options:
- Cheap "emergency" compressors sold at stores like Walmart. These are painfully slow, and are not designed to inflate four tires in a row. There's a fair chance the compressor will overheat and die before you get back to street pressure.
- High capacity 12 volt compressors. These usually have clips to get power straight from the battery and are intended for airing up multiple tires. Most will have a rating to give you an idea what tire size they are intended for. Ignore the "PSI" rating, what you want to know is the air flow (usually listed as CFM). Duty Cycle (how long it can run without stopping to cool down) is also good to know, but can be hard to find info on. ViAir is one of the best known brands, but there are many others, including cheap chinese knockoffs on Ebay. If you go for the cheap ones be very careful to study the airflow ratings.
- Engine driven compressors. These can be purpose-built compressors, but are often simply air conditioning compressors converted for air instead of AC. The advantage of these are that they pump far more air than 12 volt compressors, to the point that they can usually run air tools. If you already have AC in your vehicle then adding an engine driven compressor can be complicated, however if you do not have AC then it is often just a matter of buying the factory brackets and compressor from an auto wrecker plus a kit that contains the necessary controls and connectors.
- High pressure CO2 tanks. Often referred to by the brand name "Power Tank", these are similar to scuba tanks and can air up tires faster than all but the most powerful engine driven compressors. The advantage of them is that you don't need to modify your vehicle in any way, the disadvantage is that if you may forget to take the tank to get filled when needed. Usually you get them filled at a welding gas supply shop.
- Foot or hand pump. Not really an option but I'm including it to be thorough. I can't tell you how long it will take to inflate a set of large tires with a manual pump because I don't know anyone who has actually done it. I'm guessing about an hour, but you will likely give up from exhaustion before you get done anyway.