How to pick the right tires for your vehicle

Our recent cold weather snap was blessedly ice-free, but ice and rain highlight traction problems that are a year-round issue.  If your vehicle is functioning correctly then your tires are the only part touching the road, which means four little areas, each only about the size of a paperback book, are all that’s keeping you in contact with the road and in control. The proper choice of tires is critical, but not all tires are created equal.  The correct tire depends on your vehicle, your driving habits, the area of country you live in, and more.  It’s a lot of information to balance, so we put together a primer that will be useful for anyone needing to replace their vehicles’ shoes…

Before we start telling you about where the rubber meets the road, it would be helpful to define a few basic terms.  A tire’s description and specifications can be found in its sales literature, on the sticker applied to a new tire’s tread, or on the side wall of the tire. There are specifications that document everything from the physical dimensions of the tire to its usage, speed rating, load rating, treadwear rating, traction and temperature rating. The most permanent record of these specifications is molded into one of the sidewalls of every tire.  (A note- these specifications are only on one side of the tire.  Tires can be mounted such that you can’t see the specs on the tires on your vehicle; they may be mounted facing inboard).

One other thing… you may get advice from friends, the internet, or even mechanics about what tires to buy.  While you may have many options for quality and types of tires, certain specifications are specific to each vehicle; size, speed rating, and load rating for starters.  Your individual vehicle’s tire specs can be found on the driver’s side door pillar, glove box door, or in your owner’s manual, and you should never go outside these recommended standards!  Of course, you can always call our salaried Service Advisors to get guidance on the proper tires for your vehicle.  And now, without further ado, we plunge into the world of tire descriptions and specifications…

What your tire specification numbers mean

Tire specifications cover seven basic points:  Size, Load Rating, Weather Rating, Speed Rating, Treadwear, Traction, and Temperature.

Size

All tires have size markings, for instance “195/75R14” or “P185/65R14”.  Each of those numbers refers to a specific dimension on the tire.  Let’s take the example of “195/75R14” and go through each number…

• “195″ is the width (in millimeters) of the tire at its widest point.  The widest point is at the “bulge”, not at the tread.
• “75″ is the aspect ratio, the ratio of the width to the height of a tire.  It’s the distance from the bead of the tire (the part of the tire that matches against the rim) to the ground, divided by the tire’s width (the 195 number above).  So in this case, the ratio is 3:4, or 75 percent meaning the tire is 75% as tall as wide.  Tires with the same aspect ratio get wider as they get taller.
• “R” means a radial tire.  Sometimes you’ll also see “P” (passenger) or “LT” (light truck) as well.
• “14″ is the mounting diameter, or the size of the hole in the tire.  It’s also the size rim you’ll need for a given tire.  Remembering that tire widths are measured in millimeters, guess what units they use for mounting diameter?  Inches, of course!
  

Load Rating

The Load Rating is a comparison of the relative load carrying capabilities of the tire.  The higher the tire’s load rating, the more it can carry.  Typical passenger and light truck load ratings range from 71 to 110, or 761-2337 pounds.  Load Rating requirements vary by vehicle model.  Always get the proper load rating for your vehicle!  A common example of a load-rating mistake happens on the Toyota Prius.  Although it’s a compact car, the Prius is surprisingly heavy and needs a higher load-rated tire.  For example, the Prius (a very heavy vehicle) should use an 89 rated tire, while the Corolla can use just an 87.

Weather rating (AKA: mud and snow rated)

All-Season rated tires are marked with the M/S (mud and snow) designation on the tire sidewall.  M/S tires are specially designed for traction in wet or slippery conditions. Special tread patterns and rubber compounds are used that maintain pliability in cold weather and minimize the tradeoff between winter grip and dry wear.  In the Northwest everyone should run All-Season rated tires.

Speed rating

The speed rating designates the tires ability to shed heat built up during higher speed operation.  Some tire sizes will have limited speed rating choices, for example, most low profile tires will come with HR or higher.  The price goes up along with the speed rating, so don’t buy a higher speed rated tire than is recommended for your vehicle.  In most cases the lowest speed rating will easily cover normal driving.  After all, how often do you drive over 100mph continuously for an hour?  Even if you were to run an SR-rated tire at speeds over 100mph for a sustained period the tire would probably not fail.  The speed ratings are…

SR= 105 mph      HR= 115 mph    

TR= 125 mph     VR= 150 mph     ZR= 180 mph

Treadwear

The larger the treadwear number, the longer the tire will last. The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course.  For example, a tire graded 150 would last 1½ times as long on the government course as a tire graded 100.  Actual results will vary, but here’s a rough gauge of the numbering system:

A “200” treadwear number is the absolute minimum you should ever get.  We recommend treadwear ranges from 360-540.

Traction

The traction grades, from highest to lowest, are AA, A, B, and C. This rating represents the tires ability to stop on wet pavement as measured under controlled conditions.  A tire marked “C” traction may have poor traction performance.  Always go with a “B” rating or higher.

Temperature

Tires are temperature graded as A (the highest), B, and C, representing the tires resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions. The speed rating and the temperature rating are related.  Always choose at least a “B” rating

Buying the tires

Once you’re armed with the proper information, it’s time to actually go shopping for the tires.  You’ll find plenty of ads in the newspaper or on the internet, so you’ll have plenty of choices where to go.  While we’re big advocates of buying local, when it comes to tires you should buy from national brands you’ve heard of.  The quality will be more consistent, but it’s also much easier to get warranty support for a national brand like Michelin, Dunlop, Cooper, Goodyear, or Firestone than a Solar, Vixen, Jupiter, Pneumant, or other off-brand tires. Wherever you go, make sure to ask some basic questions:

• How much is the tire?
• Does that price include mounting and balancing?
• If I buy your tires how much is an alignment?
• Do you rotate and balance your tires for free?
• Do you repair your tires for free?
• Can I purchase road hazard insurance for your tires?
• How long will it take to have services performed?

Caring for your tires

Once you’ve made your purchase, some simple things can extend their useful life…

• Make sure to have the alignment checked and/or corrected when you purchase new tires
• Keep tire air pressure set to manufacturer’s specification (usually 28-36psi for passenger tires; higher for truck tires.  32psi is a good average pressure)
• Rotate, balance and inspect tires every 6,000 miles.
• Never run a low or flat tire.
• If the steering wheel is off-center or the car pulls have it checked ASAP.
• If you hit a curb, huge pothole, or other object have it checked ASAP

General tips

• A neat trick for looking at relative value between tires is like unit pricing at the grocery store. Take the treadwear number and divide it by the cost of the tire. The higher the result, the lower the per-mile cost. You can compare any tire value by using this method, even tires of different cost and treadwear numbers.
• Tires are not an area to economize.  Knowing what the numbers on your tires mean can give you the means to buy a better tire at a lower price, but it’s amazing how much more quality can be purchased for just a few extra dollars per tire!
• Never mix tire sizes on any vehicle!  Modern vehicles use tire sizes in many of their monitoring systems, and varying tire sizes can affect their results.  Even older vehicles without computer monitoring can have severe drivability and braking issues with mixed tire sizes
• Please don’t buy recap tires! For a few dollars more one can have a real tire. The savings don’t justify the risks involved.
• All cars have tire fitting information stickers with information like proper inflation pressures and acceptable alternative tire sizes for the vehicle.  The stickers are usually either in the driver’s door jamb or the glovebox door.
• Tire manufacturer’s mileage warranties are tricky. The rating is subjective and may not accurately reflect the service the tire will deliver. The warranty is for material defects and does not cover wear from improper inflation or alignment problems.  Manufacturers can claim whatever they want for a mileage warranty, so check out the warranty but look at the treadwear number for a better idea of tire longevity.

Following these tips will help you get the best performance and longest life from your tires.  It’s good to know all this, but you don’t really have to remember it all… you can always call us and we’ll answer any questions you might have!