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Are your tires safe? (Part I)

Tires are round and black and smell funny. Everybody needs them because they all wear out. That’s what I heard from Bob, the first tire supplier I every bought from. He went on to tell me my good customers will come to rely on me to select what tire is best for them, so I better learn about them. I want to talk a little about my experience with tires, specifically, how to know what tire you have, how to maintain them, when to replace them, and how to pick what you need. Since the Rubber Manufacturers Association has declared June “National Tire Safety Month,” I thought I’d do my part to increase consciousness among drivers about tire safety.

I’ll start with defining a tire by its standard designation system, or tire code. Let’s use one of my loaner cars as the example. The car is a 2000 Toyota Avalon. All car manufacturers have engineers who design what tire is best for a particular car. This info, along with designed tire pressure, is found on a placard attached to the driver’s doorjamb on most every car. For the Avalon the tire code is P205/65R15 92H.

  • P stands for passenger car (LT is for light truck).
  • 205 is the width in mm.
  • 65 is the aspect ratio which is the sidewall height relative to the width. In this case it’s 65 percent of the 205mm or 133mm. This number is small for a low-profile tire.
  • R stands for radial ply tire.
  • 15 is the diameter of the wheel the tire will fit in inches.
  • 92 is the load capacity of the tire, in this case it’s 1,400 pounds. The higher the number, the more weight it can carry.
  • H is the speed rating. In this case H is good up to 130 mph.

Now, all tires have this code molded on the sidewall. At our shop, one of the things we always do during the first visit is to record this info and make sure your car has the correct tires on it. You would be surprised what we find. Just remember this, your safest choice is to use the tire code designed (by an engineer) to fit your car. Make sure the code on the placard matches the code on the tire.

Tires are easy to maintain and will outlast your expectations if you follow a few suggestions. Rotate your tires front to back every 6,000 miles. Balance your tires every 12,000. Keep the pressure set to the design found on the placard (usually between 29 and 35 psi, or pounds per square inch). Make sure the car is aligned properly and have it checked once a year. An easy test is to CAREFULLY, on a deserted stretch of road, let go of the steering wheel at about 35 mph and see if the car drifts left or right. The road needs to be flat and most roads crown in the middle to allow for rain runoff, so don’t be fooled.

Also, be aware a low tire will cause a slight pull. Is the steering wheel centered? Have you biffed a curb lately or hammered a pothole head-on? All these add up.

At our shop, once a year we drive your car at 35 mph to check the steering wheel alignment. Every oil change we check the pressure and measure how much tread is remaining. Tires wear out. Most tires start out with 10/32″ to 12/32″ of tread. All tires have what’s called a wear bar located in between the tread every so often around the circumference of the tire. The wear bar is 2/32″ above the base of the tread. At our shop we alert you when the tread is 2/32″ above the wear bar (which is 4/32″ above the base of the tread). We feel this is the time to replace your tires for safety. Out of time for today, but check the next blog for advice on how to pick a tire for your car.