Can I use a gas station air pump on a bike tire?
Someone pointed out that it may be risky, and it might not have the right kind of nozzle, but I don't have a bike pump at the moment. Does anyone else ever do this?
The typical convenience store air hose provides 40 pounds max. My touring tires run 90-100 PSI. (But also be aware that some truck stop setups may deliver 150 PSI.) You at least need a tire pressure gauge.
@DanielRHicks does that mean there are air hoses for cars _without_ a pressure gauge? How does one use them to check their car's tyre pressures then? Do you always have to bring your own pressure gauge in a car?
The answer, in short is: Can you? In some cases, yes. Should you? In most cases, no.
The long answer: The reason you can sometimes use an automotive air-pump on a bicycle tire/tube is because they share an identical valve. (See: Schrader valve/Schrader tube in the Terminology Index). If you have this type, you will definitely be able to get air into your tubes in a pinch. However, air hoses from gas stations are usually unregulated, high-pressure & high-volume, and lack a pressure gauge. Therefore, it is much easier to over-inflate and even blow out your bicycle tire, if you were to use one.
An investment in a bicycle pump is one of the best you can make as a cyclist. Not only will it get you out of situations like this, but it will make it easier to keep your tires at the recommended pressure rating, which in turn will make it easier for you to be a more efficient (read: faster) bicyclist.
Several bicycle pumps - ideally you need a track pump or similar to keep where you store your bike, check the pressures regularly (when I was commuting by bike I did it once a week when I got home) and a pump you carry with on the bike because, if one is not racing, then its just sensible to carry a pump and a few other bits with you at all times
Note also: if you have a Presta valve (thinner valve with a captive locknut, common on road bikes), you'll need an adapter to use a gas station pump. The adapter is a cheap little $1 brass part that screws onto the presta valve
It's also worth noting that many gas station pumps will not go over about 80psi. That means that even if you have Schrader valves or an adapter, you won't be able to get optimum pressure in road tires. It may be enough to get you home, but you'll have to be extra careful about bumps.
For completeness, the answer seems to depend on the country and the corresponding pump technology of its gas stations. Reading the answers here took my by suprise. Since I can think, I only buy tires with a Schrader valve in order to save me from the laborious act of using a bicycle pump. I am from Germany and most of the time, you'll find such devices at gas stations.
In Australia almost every service station has a digital air compressor. The danger with using them on bikes is that they work by reading the current pressure, then dumping a huge amount of air in at once, then reading the pressure again and so on. They're designed for cars so they could well dump way too much air in on the first pump and blow the tyre.
With experience, your fingers are the best pressure sensor, and right technique is the key. With the digital service station pumps, I just dial the highest pressure (usually 80 psi) and pump with one blow, feeling the pressure as it goes, disconnecting when enough. This, of course, mostly works with MTB tyres; for road ones, the max pressure is not sufficient anyway.