Very important. Also very easy. If you have a good gauge, you can do this yourself. Shoot for once a month, when the weather changes, and before any long road trips. Do this when the car has not been driven for a few hours, or else just a few blocks. Find out the recommended pressure by looking in your manual (the number on the tire is the max allowed) for where this is printed on your car. When you visit us, ask us to check it again, which will help you check the accuracy of your gauge. Too much air means your car will bounce and be hard to control; too little can lead to overheating and possibly even the dreaded and dangerous tread separation.