If you pop a tire on a rental car, the first thing you should do is call the rental company. They will likely have a 24-hour emergency line that you can call. If not, find the number for roadside assistance and give them a call. Once you're on the phone with the rental company or roadside assistance, they will help you figure out what to do next. In most cases, they will send someone out to change your tire for you. However, if you're in a remote location or it's after hours, they may advise you to change the tire yourself and bring the car back to the nearest location when it's open.