The spare tire serves as a back up in case your car has a flat. There is nothing more annoying than a flat spare when you have a flat tire. A functional spare is a comforting accessory, but an underinflated or dry rotted one is worthless.
Imagine this. You are on a long trip through the desert. You are driving along, enjoying the scenery, when you suddenly notice you have a flat. You pull over to check it out, and indeed, you have picked up a roofing nail in your right rear tire. You curse the developers for building houses in the desert, then proceed to pull all of your luggage that you so carefully packed out of the rear of the car. You pull out your cookie-cutter spare, only to find... that it is flat too. And your cell phone doesn't seem to have coverage out here... Don't let this happen to you. Check the inflation pressure of your spare today and make sure it is at the level stated on the side of the spare (should be about 60 PSI).
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By avoiding the following pitfalls, you can be assured that your spare tire is as capable as his big brothers.
UNDERINFLATION Underinflation is the culprit in most bad spare scenarios. If your spare is low, it may shred on the way home or to the service facility. The distance you can travel before this happens is directly related to the tire's inflation level. Check the pressure of the spare, as well as the other four tires every month or two.
DRY ROTTING Tires, like clothing, tend to deteriorate with age. Although this problem is not as common as underinflation, it bears consideration. Tires do have a shelf life. After a period of time, they may begin to develop small cracks in the sidewall, your first clue to this condition.
INACCESSIBILITY The leading reason spare tires fall victim to underinflation and dry rotting is inaccessibility. If you do your own vehicle maintenance, clear out the trunk and check that "Mickey Mouse" tire. If you take your car to a shop, most automotive technicians are happy to check your spare if they can get to it. However, few will move your cargo for the sake of your spare.
FINAL NOTES 1) Some space saving spares are made to travel up to 3,000 miles at highway speeds; most are limited to 50 m.p.h. It is, as car makers state, for temporary use. Replace it with a full-size tire as soon as possible. 2) Keep your compact spare and its wheel together and do not use them on another car. 3) Do not use tire chains on the space saving spare. They won't fit and will damage the car as well as the chains. 4) Don't even think about driving through a car wash that pulls the car along guide rails. The spare can get caught on the rail and damage the tire, wheel and possibly other parts of your car as well.
Remember: a flat tire in the trunk is about as useful as a flashlight without batteries.