All tires wear out eventually and sometimes damage occurs.  The most important thing is to determine if your tires are safe to be driven on or should be replace.  Here are a couple of tips to help you make that decision.

If your tire is damaged
There's a good chance your tire can be repaired if:
                * The damage is only in the tread of the tire and not in
                    or near the sidewall.                                   
                * The puncture is smaller than 1/4 of an inch.
                * The tire has not been driven on when flat (run-flat).
Have an authorized tire dealer dismount the tire from the wheel and inspect the tire from the inside.  The tire needs to be inspected from the inside because any internal damage to the tire is not visible unless the tire is dismounted.

The correct way to repair a tire is to have the tire patched from the inside.  If anyone ever offers you a plug repair refuse.  Plug repairs do not involve taking the tire off the wheel and inspecting the inside of the tire.  A plug is simply inserted from the outside of the tire through the punctured area.  Also, plug repairs are unreliable in that over time the have a tendency to start to leak, causing the tire to go flat.

If the tire is worn
It is recommended that tires be checked once a month for visible damage and excessive wear.  There are a couple of ways to tell if the tire is worn out:

--Check the wear bars-- These are small bands that appear in the grooves across the tread of the tire.  When the wear bars are even with the tread, approximately 2/32-inch of tread is left on the tire.  If this condition exists, it is time to replace the tire.

--The penny trick-- Another way to tell if the tire is worn out is to insert a penny into the shallowest tread groove with Lincoln's head facing down.  If the top of the head is visible it is time to replace the tire.

What to know before you go to the dealer

Your tire size
Knowing your tire size before you go to the dealer will help you save time at the tire dealership and allows you to make an informed purchase.  Your vehicle's original equipment size can be found on the tire placard located on the drivers door jam, inside the fuel hatch, or on the glove box lid.  If you can't find it in either one of these places, check the owners manual.  You can also check you existing tire's sidewall markings.  There are also a couple of things you need to know if you are interested in a size other than you vehicle's original equipment size, or are upgrading you wheels.  With the complex computer controlled systems of today's vehicles it is extremely important that you take extra care if changing the size of you tires.  Most vehicle's ABS, speedometer, and transmission are all based on how many revolutions the tire makes per minute (rpms) and this is programmed from the manufacturer based on the original equipment size tires.  Once you change tire size the rpms of the tires change and the ABS system, speedometer and transmission will not function properly.  When changing from original equipment size tires it is crucial that you have the vehicle's computer reprogrammed for the size of tire that you are putting on the vehicle. 

Another aspect to consider concerns having a vehicle with all-wheel-drive or 4-wheel drive.  It is recommended that to prevent damage to the drive train all the tires should be the same brand, model, and size.  What this means is that if you are considering just replacing one or two tires, they should match exactly what is already on the vehicle. 

Your tire type
The first question you will probably be asked when you get to the tire dealership is what type of tires are you looking for.  What the dealer is referring to is categories such as all-season tires, winter tires, performance tires, etc.  Click on this link for an explanation of tire types.  The most important thing is that your new tires meet your needs.  Before you purchase your new tires, think about the best and worst conditions you think you will be driving in.  The more information you give to your dealer, the easier it will be for him to find you a tire that will be what you want.