A flat tire is something nobody wants because a flat tire will leave you stranded along side the road. When a tire loses all its air, is loses its buoyancy and the ability to support weight. Unless the tire is a special kind of tire called a Run-Flat, the sidewalls are not strong enough to support the weight of the car unless there is a certain amount of air pressure inside the tire. So a puncture or leak that allows the tire to lose air will cause the tire to collapse and go flat. Any tire, new or old, can go flat if it is punctured or leaks air. New tires have thicker treads so are more resistant to punctures than worn tires with thinner treads. But the deeper treads on a new tire can also channel sharp objects into the tire actually increasing the risk of a puncture if you drive over a nail or other sharp object. If a tire goes flat while driving, you will hear and feel a thump, thump, thump vibration from the suspension. A flat front tire will usually cause a hard pull towards the side that has gone flat. If a tire has gone flat while the vehicle is parked, hopefully you'll notice it before you try to drive away. If you don't, you will immediately feel and hear the thump, thump, thump of the flat tire. DO NOT CONTINUE DRIVING ON A FLAT TIRE! Driving on a flat tire will quickly ruin your tire. Without any air support inside the tire , the sidewalls of the tire will be pinched between the road and the edges of the wheel rim. Driving even a short distance (say more than 1/2 chilometro) may be enough to cut or destroy the tire. And if the tire comes off the rim, which a flat tire can do, you may end up damaging your wheel, too. Causes of Flat Tires Common causes of flat tires include: Leaky valve stems. There may be cracks in the rubber stem, a poor seal between the valve stem and wheel (due to corrosion or wheel damage), or an internal air leak in the valve stem because the valve is loose, faulty or jammed with dirt. Making sure the valve stem is covered with a cap will keep dirt out and help keep air in. This type of leak can be repaired by replacing the valve stem, or the valve assembly inside the valve stem. Punctures in the tire caused by driving over sharp objects. Road debris includes junk like nails, screws, steel wire from exploded truck tires, broken glass, sharp rocks, etc. Try to avoid running over debris in the road if you see it and can react in time (which is hard to do when driving in heavy bumper-to-bumper traffic). This type of flat can be repaired by patching or plugging the tire, or replacing it if the tire is too badly damaged to be repaired. Bead leaks between the tire and wheel. This is often due to rust or corrosion on the wheel, but can also be caused by a bent rim (hitting a curb or pothole). Air leaks here can also be caused by a damaged bead sealing surface on the tire, possibly the result of mishandling when the tire was originally mounted on the rim (not using a bead lubricant, attempting to force the bead over the rim, using the wrong mounting hardware). This type of leak may require dismounting the tire and cleaning the rim and bead surface of the tire. If the rim is bent or damaged, the wheel should be replaced. If the bead surface on the tire is damaged, the tire will have to be replaced. Wheel air leaks. Aluminum alloy wheels can be porous and slowly seep air over time. Adding a sealer to the tire will often cure this type of leak. Or, the tire can be dismounted from the wheel so the inside of the rim can be painted or coated with sealer. Somebody intentionally let the air out of your tire, either as a prank or to send you a message (like Don't Park Here!). No repairs are needed for this other than to reinflate the tire with air (use a pump, portable tank or aerosol can of tire inflator/sealer). Be careful where you park your vehicle next time! What To Do If You Have A Flat Tire While Driving Slow down and pull over to the side of the road as soon as it is safe to do so. DO NOT stop in the middle of the road, especially if you are on a busy highway or expressway. That's a good way to get rear-ended or killed! Pull off on the RIGHT shoulder of the road, and try to get your vehicle as far OFF the highway as possible. This will hopefully reduce the risk of someone running into your parked vehicle. It will also leave some room if a tire on the left side of your vehicle needs to be changed. Turn on your hazard flashers so other drivers will see you. Raising the hood is also a good idea as this is a universal signal for help. If it is night or visibility is poor, and you have a safety flare, reflective triangle or portable warning light in your trunk, place one of these safety warning devices some distance behind your vehicle to alert oncoming drivers. You now have to decide whether to change the flat tire yourself, or to call for assistance. If you have never changed a flat tire, or you lack the physical ability to do so, or your vehicle has no jack or spare tire, the choice has already been made for you. You will have to call for help on your cell phone, or wait for help to arrive. In some areas, there may be call boxes placed at intervals along expressways that a stranded motorist can use to call for help. If you don't see any call boxes and don't have a cell phone, you'll have to wait for a cop to drive by, or a motorist assistance truck to come by, or a Good Samaritan to stop and offer assistance. BE CAREFUL because you don't always know the motives of a person who may be offering to help you. Most people are good, honest people. But some are not. If it is safe to do so, you should get out of your vehicle and stand back some distance from the highway until help arrives. How many cop shows have you seen where some idiot plows into the back of a vehicle that is stopped along side the road? It happens all too often. If your stranded in a "bad" neighborhood, you might be safer waiting inside your vehicle with your doors locked. How To Safely Change A Flat Tire WARNING!: Every year dozens of motorists and Good Samaritans are killed attempting to change flat tires along busy roads. The risk is greatest when changing a tire on the LEFT side of the vehicle nearest the roadway. To minimize the risk of being hit while changing a tire on the left side, your vehicle should be pulled over as far to the RIGHT as possible to put more distance between you and passing traffic. Placing safety flares, triangles or lights some distance behind your vehicle will also help alert traffic. If someone has stopped to help you, the second vehicle should be parked some distance BEHIND your vehicle to serve as a barrier. Leave at least four car lengths distance between the vehicles so if their vehicle is rear-ended and pushed forward, nobody will be crushed between the two vehicles. The second vehicle should also have their hazard flashers on, as well as their headlights if it is dark or visibility is poor. Any passengers or others who are not involved in the tire changing process should stand well back from the road and vehicles. Somebody should help watch oncoming traffic and wave if necessary to warn other motorists to pull out and around your vehicles. The first step in changing the tire is to make sure your vehicle won't roll forwards or backwards when the flat tire is raised off the ground. Place the transmission in Park if it is an automatic, or in 1st or 2nd gear if it is a stick shift. Also set the parking brake. WARNING!: On rear wheel drive vehicles, the parking brake and transmission lock the rear wheels only. If your vehicle has rear-wheel drive, and you raise one of the rear wheels off the ground, your vehicle could roll forwards or backwards if the road is tilted or sloped even slightly and the parking brake doesn't hold. The same can happen with a front wheel drive car if your raise a front wheel to change a tire and the parking brake on the rear wheels doesn't hold. You don't want the vehicle to move when you are trying to change a flat tire. To prevent this from happening, wedge two blocks of wood, two bricks, some large rocks or other objects under BOTH sides of one of the tires on the other end of the vehicle from the flat tire. If a rear tire is flat, wedge or block a front wheel. If a front tire is flat, wedge or block a rear wheel. This should prevent any unwanted movement when the flat tire is raised. DO NOT attempt to change a flat tire on a vehicle if you are parked on a hill or slope. Move the vehicle to flatter ground if possible before attempting to change the tire. If this is not possible, call a tow truck, or attempt to reinflate the flat tire using an aerosol can of inflator/sealer. Aerosol tire sealer can provide a quick temporary fix in an emergency. But make sure the product is safe to use with TPMS sensors. NOTE: if your vehicle has a Tire Pressure Monitoring System with pressure sensors inside the wheels, DO NOT use aerosol inflator/sealer unless the product says it is safe for TPMS applications. The sealer in some of these products may gum up the sensors.) After blocking the wheels, locate the jack, lug nut wrench and spare tire in your vehicle. If you don't know where it is, check your owners manual in the glovebox. Jacks are usually located in the trunk or cargo area of the vehicle, and are usually hidden under a panel or cover. The spare tire may be in the trunk, mounted underneath the back of the vehicle, or hung on the rear door in the case of many SUVs. Some vehicles do not have a spare tire (MINI and Corvette are two). In fact, nearly one-third of new vehicles today are not equipped with a spare tire to save weight for better fuel economy. Many of these vehicles have run-flat tires that can support the vehicle for distances of up to 50 chilometri at speeds of up to 45 mph. But if the vehicle does not have run-flat tires, or the original run-flat tires have been replaced with ordinary tires, your only options if you have a flat are to reinflate the tire with a can of infla…

Fonte: AA1Car.com