Have you ever found yourself in the unfortunate situation of having one or two tires leaking and old?  When you go to the local tire store, the sales associates will always try and up-sell you on purchasing a whole set, but luckily, there's a way that you can save some money and only get two. As a disclaimer, if all of your tires are worn down and don't pass the “penny test” then you should replace them all.  That's when you hold a penny so that Mr. Lincoln is upside down and put it between the treads of your tire.  If you can see the top of the former President's head, then it's time for new tires.  It’s extremely important to have good tires; they are the most important part of your car when it comes to driving and safety, and having good tires could be the difference between life and death. But sometimes you really do only need two.  Maybe a nefarious youngster slashed a tire in the night, you picked up a nail on the way to work, your teenager damaged one botching a parallel parking job, or a bad alignment job has made two of your tires wear out faster than they should.  For these kinds of situations, it's better to buy two than have to shell out for a whole set. The trick to buying a pair of tires is getting ones that fit and having them installed properly.  If you have a normal, 2-wheel drive car, then you can get away with replacing the damaged tire and the one opposite to it.  Most people like to have the new tires installed in the front and have the rest rotated appropriately because you get the best handling out of that arrangement.  However, if you have a 4-wheel drive car, then you're out of luck—because the car relies on all four tires being the same to offer stability and traction, all tires need to be replaced at the same time.  It's annoying, but it's the price for the extra safety.  In either case, you should never replace just one tire because it will, at best make the car drive strangely, and at worst significantly compromise the car's handling and braking distance. Once you have your new pair of tires everything is hunky-dory, right?  Well, not quite yet.  Your car handles the best—and is safer—when it has the same tires on all four corners.  If the tires all have around the same amount of wear on them then yes, you can get away with driving until you need a new set, but otherwise, it is best to replace to other two as soon as they start getting close to the end of their useful lives.  If you're using the penny test, then replace the older tires when you can see the top of old Abe's ears. Yes, it's a pain in the butt to have to buy new tires, but sometimes you can get away with only replacing two.  It's perfectly safe as long as you drive safe as always, and follow the basic rules—don't replace just one tire, buy two of the same brand (like the Nitto tires found here), and have them installed by a professional. Have you ever needed to replace just one or two tires?  How did you handle it?  Please share your experiences!