TIRE ABC'S

  • Cardinal Points for Proper Tire Maintenance
  • When Should I Replace My Tires?
  • Load Index/Speed Rating
  • Sidewall Info
  • Sizing Systems
  • UTQG System

Key Points for Proper Tire Maintenance

Check tire pressure regularly (You will observe the inflation pressures for the Original Equipment Tire size on the vehicle, usually on the door placard, a sticker often plant on the driver's door frame, or dorsum edge of the door. This will prove the tire size that came originally on the vehicle and the air pressure to comport the load required of this vehicle.)

Rotate the tires every 8,000 KM (Tip: Make your beginning rotation before you attain the viii,000 KM mark. When the tread is at full depth the tire is virtually susceptible to irregular wear. Making the kickoff rotation early will aid negate any irregular wear that is in the process of developing.) Check the tread wear often.

Have the wheels alignment every two years or if you suspect the pause has been damaged, also when a new set up of tires is installed.

Have the wheel counterbalanced when the tires are new and again if you notice a "shimmy" in the steering wheel.

When Should I Replace My Tires?

According to nigh states' laws, tires are legally worn out when they have worn down to 2/32" of remaining tread depth. To help warn drivers that their tires have reached that point, tires sold in North America are required to have molded indicators called "article of clothing confined" across their tread design from their outside shoulder to within shoulder. Vesture bars are designed to visually connect the elements of the tire's tread blueprint and warn drivers when their tires no longer meet minimum tread depth requirements.

However, as a tire wears information technology is important to realize that while its dry out traction and handling volition improve…its ability to perform in pelting and snow will diminish. At 2/32" of remaining tread depth, resistance to hydroplaning in the rain at highway speeds has been significantly reduced and traction in heavy snowfall has been about eliminated.

If pelting and moisture roads are a business, yous should consider replacing your tires when they reach approximately 4/32" of remaining tread depth. Since water tin can't exist compressed, you need enough tread depth to permit information technology to escape through the tire's grooves. If the water can't escape fast enough your vehicle's tires will be forced to hydroplane (actually float) on top of the h2o, losing traction.

If snow covered roads are of concern, y'all should consider replacing your tires when they reach approximately six/32" of remaining tread depth to maintain good mobility. The reason that you need more tread depth in snow is because your tires need to compress the snow in their grooves and release information technology as they curlicue. If at that place isn't plenty tread depth, the "bites" of snow your tires can have on each revolution will be so modest that your traction will exist reduced. Considering tread depth is an important element for snow traction, winter tires showtime with deeper tread depths than standard all-season or summer tires. Some wintertime tires even have a serial of wear bars molded in their tread pattern indicating approximately 6/32" remaining tread depth.

What is the right size for my vehicle?

A tire'south commencement requirement is that information technology must be able to carry the weight of your vehicle. No matter how expert a tire you lot select, if its capabilities are "overworked" just carrying the load, it will have piddling reserve chapters to help your vehicle respond to quick emergency. And so when you are in the selection process, brand certain that your new tire's size is designed to carry the weight of your vehicle! Don't undersize.

The other size consideration is overall tire diameter. Since many of the functions of today'due south vehicles are highly computerized, maintaining accurate speed data going into the calculator assures accurate instructions coming out. And an important office of the speed equation is your tire's overall tire diameter. For cars and vans, staying within a ±2% bore change is desirable.

Some plus sizing on selection-ups and sport utility vehicles (SUVs) has traditionally utilized sizing outside of this ±2% diameter assart. The critical factors of business organization when irresolute from the Original Equipment size are: 1. to ensure the tires carry the load (and potential load) for the vehicle; ii. to ensure the vehicle stability has not been compromised; iii. the acceleration and braking have not been compromised by the change; and 4. at that place is no interference of the tires with the body, suspension, or chassis of the vehicle.

Most tire dimensions tin can be calculated. See the section on "How do I calculate tire dimensions?"

While at commencement a ±2% diameter increase or reduction in tire diameter may sound very limiting, in nearly cases it allows approximately a ±ane/2" diameter change.

Additionally to help with the selection of substitute sizes, a arrangement called "Plus Sizing" was developed. Employ Plus Sizing to take into account the diameters of the available tires and the wheels, and this helps select the appropriate tire width that ensures adequate load capacity. Maintaining the tire'due south overall diameter helps maintain accurate speed data going into the computer.

How many tires exercise I need?

Since tires impact the personality and performance of your vehicle, all four tires should be as identical equally possible or treatment issues may arise. If your tires don't friction match, information technology is possible that one end of your vehicle won't respond as speedily or completely as the other, making information technology more difficult to control.

JUST ONE TIRE?

If your tires have a lot of remaining tread depth, merely you need to replace just 1 that has been damaged by an accident, route hazard or a vandal, you should replace it with a tire that exactly matches the others. Select a replacement tire of the same brand, line, size and speed rating. While there may exist a less expensive tire bachelor, it wouldn't be a bargain this time because it would exist unlike than the other three tires on your vehicle.

A PAIR OF TIRES?

If two of your tires have a lot of remaining tread depth, merely you need to replace the other 2 because they were damaged or have worn out, you should supervene upon them with a pair of tires that come up as shut as possible to matching your existing tires. While identical new tires are desirable, others of the same size and type tin also provide adept results. Simply consider selecting new tires that are from the same tire category as your existing tires. New tires should be installed on the rear axle. While your vehicle is existence serviced inquire your mechanic why one pair of tires have worn faster than the other pair. Was it acquired past a lack of tire rotation, out-of-spec bicycle alignment or loose mechanical parts? In one case the problem has been found, information technology can be corrected earlier it damages your new tires. Proceed in mind that your ultimate goal is that all of your tires always clothing out at the aforementioned time so they can exist replaced as a fix.

A Fix OF TIRES?

If all of your tires are wearing out together, yous have the greatest flexibility in tire selection. If you were happy with the original tires, simply replace them. If you lot want longer treadwear, a smoother ride or more handling, there are probably tires that volition help you lot attain that.

HOW Practice I Summate TIRE DIMENSIONS?

Example...185/60R14 85H or 185/60HR14 The starting time number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, separate by 25.4 in the example higher up, the width is 185mm or vii.28".

The second number is the attribute ratio. This is a ratio of sidewall height to width. In the case above, the tire is seven.28" broad, multiply that by the aspect ratio to find the height of one sidewall.

In this case, 185x0.lx=111mm or seven.28"x0.60=four.36".

The last number is the bore of the wheel in inches.

To figure the outside diameter of a tire, accept the sidewall top and multiply by ii, (call back that the diameter is made upward of 2 sidewalls, the one above the wheel, and the one below the wheel) and add the diameter of the wheel to become your answer.

185mm x .60=111mm 10 2=222mm + 355.6mm (fourteen") = 577.6mm or 22.74" (((185 X .sixty) X 2) / 25.iv ) + 14 = 22.74

A shorter formula exists that makes this a little easier. It is Section Width (SW) times the Attribute Ratio (AR) (total number) divided past 1270 (a constant that takes care of the percentages, the two sidewalls, and the conversion to inches), plus the rim diameter (RD) (in inches), which gives the Outside Diameter (OD). Here is how information technology would wait with the same example in a higher place. ((SW X AR) / 1270) + RD = OD

((185 X lx) / 1270) + fourteen = 22.74 inches

Load Index/Speed Rating

The speed rating is the maximum service speed of a passenger auto tire. Low-cal truck (LT type) tires may not exist speed rated. Here is a listing of rating indicators and their mile-per-hour equivalents. This rating arrangement applies to all tire makers.

RATING MAXIMUM SPEED
Q 99 MPH
S 112 MPH
T 118 MPH
U 124 MPH
H 130 MPH
V Higher up 130 MPH (WITHOUT SERVICE DESCRIPTION)
Five 149 MPH (WITH SERVICE DESCRIPTION)
Z 149 Above 149 MPH

When "ZR" appears in the size designation with the service clarification, the maximum speed is as indicated past the service description.

TIRE DESIGNATION MAX. SPEED
P275/40ZR17 93W 270 KM/H (168 MPH)
P275/40ZR17 93Y 300 KM/H (186 MPH)

For tires having a maximum speed capability above 240 km/h (149 mph), a "ZR" may appear in the size designation. For tires having a maximum speed capability to a higher place 300 km/h (186 mph), a "ZR" must appear in the size designation. Consult the tire manufacturer for maximum speed when there is no service description.

SPEED SYMBOL SPEED (KM/H) SPEED (MPH)
5* ABOVE 110 ABOVE 130
V 240 149
Z** Above 240 ABOVE 149
West 270 168
Y 300 186

Exercise SPEED-RATED TIRES Cost More than OTHER RADIALS?

Tires are highly engineered products designed to support the weight (load) of the vehicle, its passengers, and its contents. In addition the tires take the responsibility to make the car accelerate, decelerate (or stop), and corner under a wide multifariousness of conditions and road conditions. They must practise this nether normal conditions and in evasive maneuvers. We as drivers and passengers also ask the tires to comport us in quiet comfort and security and provide a reasonable tread life. As nosotros increase the tire'due south performance adequacy, moving up through the speed ratings from non-rated passenger tires to the highest of the Z-Rated tires, the prices of tires usually follow suit. However, one of the best values today is a tire designed, engineered, and produced for your vehicle and the fashion you drive. While the toll for the most of life's necessities have increased over the years, tire prices have continued to exist quite reasonable.

MY CAR CAME EQUIPPED WITH V-RATED TIRES. CAN I SWITCH TO A LOWER RATING?

We practise not recommend downgrading the speed ratings of tires for your vehicle. Speed Ratings are a immovability standard defining a tire's power to withstand, or control, heat and growth. The components engineered to practice this add together performance characteristics and benefits to the tire commiserate with each speed rating level. This is not to say that all tires of equal speed rating are equal in all respects. Nevertheless, within a tire manufacturer's line of products an H-Rated tire usually handles, or "performs" ameliorate than an S-Rated tire, and a Z-Rated tire normally handles improve (has crisper steering response and overall greater cornering grip) than an H-Rated tire. Each tire line (or model) within a speed rating tin can be designed and engineered to provide specific performance characteristics depending upon the typical user's wants, needs, and desires. You should attempt to match the tire'south handling personality to that of your machine. Your motorcar is probably one of the almost expensive purchases you accept made. Ensure that yous maintain the functioning characteristics yous like about the vehicle by selecting a tire with equal or greater performance capabilities.

Sidewall Information

PASSENGER TIRE SIDEWALL EXAMPLE P225/60R16 92V

"P" ways this is a passenger car tire (as opposed to a tire made for a truck or other vehicle). P-metric is the U.S. version of a metric tire-sizing system.

"225" Department Width: The width of the tire in millimeters from sidewall to sidewall. This measurement varies depending on the width of the rim to which the tire is fitted: larger on a wider rim, smaller on a narrow rim. The number on the side of tire indicates the width, measured with the tire fitted to the recommended, or pattern, rim width.

"60" Aspect Ratio: The ratio of pinnacle to width; this tire's sidewall height is 60% of its width.

"R" Structure: How the plies are constructed in the tire carcass. "R" means radial. "B" in place of the "R" means the tire is belted bias structure. "D" in identify of the "R" ways diagonal (or bias) construction.

"16" Rim Diameter: The diameter of the wheel (or rim) in inches.

"98" Load Index: Load Index is a rating which reflects the load chapters of the tire. This tire has a load capacity of ane,653 lbs. For a more consummate list run across the nautical chart under Load Index and Speed Rating.

"V" Speed Rating: This tire has an industry-standard maximum service speed of 149 mph. Tires using an older European system comport the speed rating in the size clarification: 225/60VR16. Different letters correspond to different maximum service speeds.

The letters "DOT" certify compliance with all applicable safety standards established by the U.S. Department of Transportation (DOT). Adjacent to this is a tire'due south identification or serial number; a combination of numbers and letters with upwardly to 12 digits.

The sidewall also shows the type of cord and number of plies in the sidewall and under the tread.

Sizing Systems

Four sizing systems exists for passenger tires today, but we'll explicate the two most commonly used:

P-METRIC

  • Examples: P215/65SR15, P215/65R15, P215/65R15 95S
  • P = Passenger Car Tire
  • 215 = Section Width in Millimeters
  • 65 = Attribute Ratio
  • R = Radial Construction
  • 15 = Rim Diameter in Inches
  • 95S = Service Description (Load index and Speed Rating)

EUROPEAN METRIC

The aspect ratio is assumed to be 82 if not present in identification number.
  • Examples: 155SR13, 155R13, 155R13 78S
  • 155 = Section Width in Millimeters
  • S = Speed Rating
  • R = Radial Construction
  • 13 = Rim Diameter in Inches
  • 78S = Service Clarification (Load index and Speed Rating)
With the attribute ratio included:
  • Example: 185/70SR14, 185/70R14, 185/70R14 88S
  • 185 = Section Width in Millimeters
  • 70 = Aspect Ratio
  • S = Speed Rating
  • R = Radial Construction
  • 14 = Rim Diameter in Inches
  • 88S = Service Clarification