It has been several years now that new cars don't come with a spare tire. However, if you'd like to add one to your Jeep Commander it is quite simple. You'll need to buy an install kit that mounts the spare tire on the back of the car. There is basically nowhere else to mount the tire and be able to use this. If you decide to go this way it is important to buy a cover for your spare tire. This protects the tire from weather and sun damage.
The new cars all come with run-flat tires that will allow a person to drive on a flat tire for a certain number of miles. This will depend on the tires the car manufacturers use on their cars. I know that some run-flat tires will go up to 100 miles if you are in the middle of nowhere and can't find a way to change out your tire.