Auto parts manufacturing especially tire manufacturers rate each model tire for the maximum amount of pressure that the tire can withstand. Most modern tires have a maximum pressure rating of at least 35 pounds per square inch (psi), which means that you can inflate the tires to 35 psi without exceeding the tire manufacturer's rating. Your vehicle's manufacturer almost certainly has listed its recommended tire inflation levels for your specific car. There will be a sticker on the frame of the driver's door listing the car manufacturer's recommended tire inflation.
Tires today have ever higher maximum tire inflation ratings -- it's common today to see tires rated for 44 psi and some are rated at 51 psi. This is important because the higher your tires are inflated, the better your car's gas mileage will be. Nevertheless, you need to weigh various considerations when it comes to tire inflation. You are always safe using the car manufacturer's recommended tire inflation. If you have a taller vehicle, such as an SUV or a four-wheel drive pickup, then stick with the manufacturer's recommended inflation. If you have any questions, go to a dealer and ask the service department for advice.
On the other hand, if you have a passenger car that has a normal height from the ground, it's safe to inflate the tires to within two psi of the maximum. I have a car with tires rated at 44 psi. At the time the car was built, there were no 44 psi tires available for this car, so the car came with tires rated at 35 psi. (The manufacturer's recommended inflation is 32 psi front and 30 psi rear.) With the 44 psi tires, I inflate them to 41 psi front and rear. This improves the car's gas mileage by 2 mpg.
All things being equal, I recommend that you buy tires with pressure ratings of at least 44 psi and keep the tires inflated to 40 psi. This recommendation is for passenger cars and not trucks -- trucks should always be inflated according to the truck's manufacturer.
RUN-FLAT TIRES
Run-flat tires will continue to work more-or-less normally if you lose the pressure in the tires. If your car has run-flat tires, this is an excellent safety feature but it comes at a complex price. For one thing, run-flat tires are very expensive to replace and not all tire shops have the equipment to replace run-flat tires. For another thing, if you have run-flat tires, you probably don't have a spare tire. Keep that in mind -- if a tire gets shredded, you will not have a replacement and will be stuck where you are.
As you can see, run-flat tires are a mixed blessing. Be aware of the price -- many people have been floored at the replacement cost of a set of run-flat tires, which can cost more than $1,000 with the labor. If I have a choice, I will use standard tires and carry a spare.
One final tire feature: Rolling Resistance
Different tires have different rolling resistances, which means that some tires are easier to roll down the road than others. Easy rolling means that you will get better gas mileage with that tire, and that's a good thing. (Running a tire at a higher inflation will almost always make it easier rolling -- that's one reason why gas mileage improves.) Unfortunately, there is no widely advertised rating for rolling resistance, so you are at the mercy of a tire dealer when it comes to discussing rolling resistance.
WHAT DO I NEED FOR MY CAR?
When you shop for tires, you should know your tire size and have some idea if you want a standard passenger car tire, a light truck tire or a performance tire. You should also know if you need tires that are "Mud & Snow" rated, usually abbreviated as M&S. If you live in an area that regularly gets occasional snowstorms, you definitely require tires that are M&S rated.If your current tires are 205/60-15 M&S rated, and you have no reason to change, then plan to get tires that are 205/60-15 M&S rated. Look for tires that have a higher pressure rating so that you can inflate them higher and get better gas mileage.
If you want to improve your gas mileage some more, look for tires that are narrower and taller. For example, instead of 205/60-15, look for tires that are 195/70-15. Taller, narrower tires will be more comfortable, cut through snow and wet conditions better and get better gas mileage. (If you ever looked at the tires on a Toyota Prius, they are tall and skinny - that's what gets the best gas mileage.) However, taller and narrower tires will have more vague handling and not feel as "sporty." It all depends on what you want.
HOW DO I CARE FOR TIRES?
The number one thing you should do to care for your tires is to check inflation once a month and keep the tires at their recommended inflation level. Not only will this give you the longest tire life, you'll also get the best gas mileage.
There are a few other things to check, too. Cars that have worn suspension and steering components (shock absorbers, struts, anti-roll bar bushings, tie rods, etc.) can have significantly higher tire wear. Cars that have poor wheel alignment will rapidly wear out tires. If your steering wheel is not lined up perfectly straight, consider taking your car in for a wheel alignment. A good wheel alignment can prolong the life of tires and get you better gas mileage to boot.
Finally, the more you carry in your car/truck, the faster your tires will wear. If you ordinarily carry around more stuff than you really need, you are wearing your tires faster than normal. In addition, the extra weight reduces your gas mileage and makes your car handle below normal. The brakes take longer to stop and the car takes longer to accelerate up to highway speed. Give your car and your wallet a break and remove any objects from your car that don't really need to be there. Do you really need that box of books in the trunk, or to carry around an extra spare tire or an old battery? Save money and take it out.
WHERE CAN I BUY TIRES?
Most car dealers can sell you tires, and there are Goodyear, Firestone and independent tire shops across the country. In addition, many Sears and Walmart stores sell tires, as do autoparts stores such as Pep Boys and Autozone. Check advertising fliers carefully for good deals and you can find a good price at any of these stores. Building a relationship with a good tire dealer is a good thing, as a smart organization will want you do come back and buy again. A good dealer will take care of you.
Another good source for tires is warehouse clubs, such as Sam's Club and Costco. These stores are downright bargains for tire labor, usually charging MUCH less for labor than more mainstream tire dealers. Warehouse clubs often have access to better tire warranties or other extras, such as free tire rotations.
If you have specialty tire needs, such as an unusual "run-flat" tire or a high-performance car, then I strongly recommend a mail order/Internet company called The Tire Rack. Not only does The Tire Rack have excellent prices and terrific online information, it can ship tires to you in a day or two. I've gone to stores that couldn't get tires for two weeks, but The Tire Rack shipped the tires to my door the next day. At an excellent price, too.
Unless I have no alternative, I will not buy used tires. Some car experts say that re-treaded tires are a good value. That may be, but I'll pay an extra $25 per tire and get new tires. The peace of mind is worth that much.
SUMMARY
The most important auto part, tires are complex things that we generally give little thought to over the years. If you need new tires, find out what size you need and study the above material about the UTQG. Make a decision about comfort vs. performance, and decide which retailer is right for you. I have been very pleased by going to wider, shorter tires for a performance-oriented feel. However, I can readily understand if you want tires that will give you better gas mileage.
Source : http://www.viewpoints.com/Auto-Parts/guides/Tires-Tires-and-more-Tires-Everything-you-need-to-know-about-car-tires-and-truck-tires
