A flat tire can turn turn your otherwise perfect day into a nightmare. When you blow a tire while driving, you'll be forced to pull over and stop your vehicle. Driving with a flat can damage the rim, preventing a new tire from fitting properly. Before throwing in the towel and calling AAA, however, you should attempt to change it yourself. Assuming you have a spare in your trunk (or elsewhere), you can change your flat tire in a few easy steps.
Loosen the Lug Nuts
Contrary to popular belief, the first step to changing a flat tire isn't jacking up your vehicle. Rather, it's loosening the lug nuts. After pulling off the road -- either to a parking lot or shoulder -- place the lug wrench into each of the flat tire's lug nuts to loosen them. Don't completely remove the lug nuts, but instead loosen them just enough so that you can easily pull them off later.
Jack Up Your Vehicle
Next, jack up your vehicle so that you'll have enough clearance to remove and replace the flat tire. Depending on your specific vehicle, it should have dedicated "joint points" where you can safely place the jack. Do not attempt to jack up your vehicle from anywhere else other than these dedicated joint points.
Remove the Flat
With your vehicle jacked up, you can proceed to remove the flat tire. Assuming you already loosened the lug nuts, the flat tire should come off with little effort. You can then place it in your trunk or backseat.
Install Spare Tire
Now it's time to install the spare tire. Even if it's a smaller "donut" tire, it should still fit on the rim. Simply position the spare tire around the rim's bolts, and then place the lug nuts over those bolts. Don't tighten the lug nuts all the way, however. Only tighten them enough to secure the spare tire in place.
Lower Your Vehicle
After placing your spare tire on the rim, lower your vehicle back to the ground. This is a straightforward process that involves reversing the direction in which you jacked up your vehicle.
Tighten Lug Nuts
With your vehicle on the ground, you can tighten the lug nuts. Ideally, it's best to tighten lug nuts with a torque wrench. If you only have a lug wrench, though, it will suffice. Just remember to tighten all the tire's lug nuts in an even pattern to ensure proper alignment.