Calculating Approximate Tire Dimensions

Most modern passenger car and light truck tires feature size designations that indicate the tire's dimensions in a combination of metric, mathematical and English systems. While this unusual combination of millimeters, percentages and inches is a byproduct of the evolution of global tire specifications, it also provides the ability to calculate/estimate  basic  tire dimensions.

Example size: 225/45R17

The first three numbers in a typical size (225/45R17) are the tire's indicated section width in millimeters, measured from sidewall to sidewall.
If you are familiar with measurements in inches, the section width in millimeters can be converted into inches by dividing it by 25.4. For example:

225mm / 25.4 = 8.86"

The second pair of numbers (225/45R17) is the tire's aspect ratio or profile. This is a ratio of sidewall height to section width. The section height's measurement can be calculated by multiplying the section width by the aspect ratio. The answer will be the height of one sidewall. For example:

225mm x 0.45 = 101.3mm
8.86" x 0.45 = 3.99"

How To Rotate Tires

The tires on your car are just as important as the car's engine. To make sure you get the  best performance out of your car, you need to take care of the tires. The tires are as responsible for the steering and   braking power as the steering wheel and the braking system. To ensure  you get the best possible  performance out of your tires, you need to rotate  them  about  every five thousand miles. You can rotate the tires of your car yourself at home; there's no need to take your car to the shop and pay an arm and a leg for it.

Tire Knowledge for Women

Vehicle maintenance isn't just for guys. Women can and should sharpen up their auto knowledge! For their own safety and know-how, here is some tire knowledge that all women should know.

Step 1

Know what the numbers on your tires mean.  Not all tires are the same. Each tire comes  imprinted with a special number on its side that provides valuable information to mechanics

  and car owners. First look for numbers on your tire that refer to its measurements. Tires come in all sizes, so if you need to buy tires for your specific vehicle, you'll need to know this number so that the tire salesman can match your tires exactly. An example of a tire number is P 235-60R-17. Here's what all those crazy numbers mean: P

Continental Evolves the Tire-Pressure Sensor - Tech Dept

Federal regulations have required some sort of computerized tire-pressure monitoring system in new cars since the 2007 model year. Most of these are active types that employ a sensor mounted to each wheel,  which in turn can relay pressures or warnings via the dashboard.

As both a maker of tires  and electronic systems, Continental is taking a more integrated approach. It plans to mount the sensors to the inside of tires instead of the current practice of mounting them to the wheels.

By coupling  the sensor  to  the tire and adding a bit of memory, the tire-pressure sensor (TPS) will be able to inform the  car of specific info about the type of tire in use. For example, it would allow the car’s  computer to adjust the top-speed governor to match the speed rating of the tires.   This would eliminate the warning stickers placed on the speedometers of cars in Europe when snow tires with lesser speed ratings are fitted to fast cars. The system could also keep track of the location of each tire and when it was fitted, thereby fixing rotation intervals and tracking tire mileage and expected life.

here’s an accelerometer in every current TPS to detect wheel motion and allow the sensor

Tires Rotation

Tire rotation or rotating tires  is  the  practice of  moving  automobile wheels and tires from one position on the car, to another, to ensure even tire wear.  Tire wear is uneven for any number of reasons.  Even  tire  wear is desirable to maintain  consistent performance in the vehicle.

Tips for recommended use of tire chains

• A torch, plastic garbage bag (or ground sheet) & (rubber) gloves will make
  fitting easier.
• Do not even try using a jack to lift your car to put chains on. Icy conditions
  make it very easy for your car to slide off.
• Diamond chains are recommended.
• Chains change your car's handling. Take time to readjust your driving.
• Do not put on chains before you need to, nor leave them on after you are clear
  of snow and ice areas. As well as wearing out your car, they damage the road

Rules for using tire chains

Important: Pre-fit chains prior to actual use!
 For your convenience and safety:

1. Consult your vehicles owners manual to see if chain can be used on your vehicle.
2. Make certain your tire chains are properly sized for your tires.  A proper fit is key to performance
3. Follow directions installing tire chains.
4. Apply as tightly as possible by hand for maximum chain life.
5. Be sure to pull off highway to safe place before installing, servicing or removing tire chains.
6. Do not deflate tires to install tire chains.
7. Drive approximately 1/4 mile. Stop & retighten.
8. Extra links may be cut off or preferably retained on the fastener arm.
9. Do not drive at high speed.  Accelerate or decelerate slowly. Avoid spinning or locking of wheels.
10. If a cross chain should fail, stop immediately.  Repair. Do not drive with a broken chain.
11. Avoid hitting curbs with tire chain.
12. Tire chains are not designed for towing vehicles.

Tire size must be known in order to select a tire chain of correct fit. For passenger cars, vans and small pick-up trucks it is important to check the owner's manual. The restricted wheel well clearance in most of today's down-sized and front drive vehicles may require  the use of SAE class "S" tire chains, as noted in the vehicles' owners manual. 

Thank you information from http://tirechain.com 

Where do I find my tire size?

The tire size is located on the tire sidewall.  In the examples above, we have circled the size in red. The size of the tire on the left is P215/65R-15. The size of the tire on the right is LT235/85R-16.

Thank you Information from http://tirechain.com

How to Install Tire Chains

How to Install Tire Chains

 

For many motorists, installing tire chains can be an intimidating, if not chilling, experience. Following these simple steps can make the job much more bearable.

Instructions 

Determine whether your car has front-wheel drive or rear-wheel drive. Tire chains always go on the driving wheels.

• Check your owner's manual for any reference to "class S" or limited clearance for tire chains. If your tires need a limited clearance product, consult the manual for additional instructions, as traditional chains aren't recommended for your car.
  
• Pull completely off the road and out of the way of traffic.
  
• Set your emergency brake and turn off the engine before you climb under the car. Passengers can stay in the vehicle or wait in a safe place away from traffic.
  
• Lay the chains flat on the ground so each side is parallel. Make sure there aren't any twists in the links.
  
• Drape the chains over each back tire, keeping the "speed hook" (or "J hook") fastener on the inside. The other side of the chains has a lever fastener with a "keeper" link.
  
• Make sure the smooth side of the cross member end hooks is lying against the tires. You'll recognize these parts when you see the chains.
  
• Reach behind each tire and fasten the speed hooks by inserting the J hooks through the third link from the other end of the chain. Pull the slack toward the outside edge of the tire.
  
• Pull your car forward several feet and pull the rest of the slack toward you. Insert the lever fasteners through the third links from the opposite ends of the outside chains and pivot the levers back on themselves, then fasten them under the keeper links.
  
• 10
  Drive forward several feet, then pull all the slack out of the chains and refasten them as tightly as possible. There should be about the same number of loose links on each side of the chains.
  
• 11
  Secure these extra links with zip ties, or remove them with bolt cutters
  
• Add rubber tighteners to lengthen the life of the chains

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Information from  http://www.ehow.com  &  http://www.carspace.com
Video Instruction

General Tire Chain Rules

General Tire Chain Rules

• Consult your owner's manual to see if tire chains can be used on your vehicle.
• Make sure chains are properly sized for your tire. Proper fit is very important.
• Install as tightly as possible by hand for maximum chain life and performance.
• Pull completely off the road and out of the way of traffic before installing, servicing, or removing tire chains.
• Do not deflate tires to install tire chains. (Tires should be normal inflation.)
• Drive approximately 1/4 mile. Stop and retighten chains. Extra links (depending on chain style) may be cut off or zip tied.
• Do not exceed 30 miles per hour. Accelerate and decelerate slowly. Avoid spinning or locking of wheels.
• If chains should fail, stop immediately and repair or remove. Do not drive with a broken tire chain.
• Avoid hitting curbs with tire chains.
• Tire chains are not designed for towing.

The dimensions of tires may vary between manufacturers and tread design profiles. We recommend that you pre-fit your chains prior to use. These tire chains may be designed to fit the largest tire profile within the tire size designation. Pre-fitting the chains will ensure that the chains will fit the tire when you are ready to use them.

Tire ChainTraction Ratings

Tire Chain Classification and Use

Definition of SAE classification

SAE class S:
Regular, non-reinforced passenger tire chains and cables for vehicles with restricted wheel well clearances.

SAE class U:
Regular, non-reinforced and lug-reinforced passenger tire chains for vehicles with regular, non-restricted wheel well clearances.

SAE class W:
Passenger tire chains that use light truck components, as well as some light truck chains.

Anti-Lock Brakes (ABS) & Four Wheel Drive

Anti-Lock Braking systems are not an alternative to traction devices. ABS assists in maintaining control and managing the vehicle's available traction more efficiently than a conventional braking system. When tire chains are installed, stopping traction for the ABS system is increased.

Although four-wheel drive and all-wheel drive vehicles have greater traction ability than two wheel drive systems, they do not have any advantages in stopping under winter driving conditions. It is recommended that all tires be equipped with tire chains on these vehicles.

 Which Tires to Chain Up

Tire chains should be installed on the vehicle's drive tires. On vehicles with front-wheel drive, this would be the two front tires and on vehicles with rear-wheel drive the two rear tires should be chained. If your vehicle has four-wheel drive or all-wheel drive, and you intend on chaining up only two of the tires, refer to your owner's manual for advice on which axle to chain up. To retain the best performance and handling from a four-wheel or all-wheel drive vehicle, install traction devices on all four tires.

Under normal driving conditions, a vehicle has about the same amount of traction at each wheel, creating a feeling of 'normal' control during braking, acceleration and cornering. Under snow and ice conditions, this balance is disrupted. If tire chains are installed on only the front tires, the rear of the vehicle can swing during braking and driving. If snow chains are installed on the rear tires only, the steering ability of the vehicle is limited. To get this balance back, the vehicle should be completely equipped with tire chains. Remember that tire chains are sold in pairs. Therefore, if you intend to install chains on all four tires, you must purchase two pair.

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Information from www.tirechainsrequired.com