How to know when your tires have had the biscuit

When is it appropriate to get new tires?

  • The image of cars on a parking

Q: My 2001 Toyota Echo still has its original tires. The summer tires only have 105,000 km on them and the winter ones about half that. My friends insist it is time for new tires. Do tires wear out while they still have tread left?

A: It is time for new tires, even though they still have tread left. Having tread is half of what makes a tire give you good grip. The other half of the equation is tread flexibility. On a microscopic level, grip works by the tire conforming to the peaks and valleys of the pavement. The tire locks onto these irregularities and then pushes off and the cycle keeps repeating as the tire rotates. Therefore, the tire must be soft and flexible.

Tires are made up of natural rubber, silica, carbon black, oil and a variety of chemicals to bond the whole mixture together. Over time, these chemicals and oils evaporate out and the tires? tread gets harder. When that happens, grip is reduced. How long this process of deterioration takes will vary widely. It depends on where your tires spend their time.

The evaporation and chemical un-bonding is hastened by heat, sunlight, ozone and touching or being near any petroleum products. All of those things occur where cars normally hang out, so tire deterioration is inevitable.

Our problem when driving is that we do not notice the gradual deterioration in grip because we drive so often. We just get used to the car not stopping quite as quick and make a mental compensation. It is not until a big emergency stop is required that the light bulb goes on. ?Wow, I?ve got no grip.? For some of us, that big emergency stop never comes, so there is no ?Aha!? moment.

So after four to five years, start checking your tires with a flashlight. Look inside to grooves at the base of the tread blocks and on the sidewall area. See if there are little spider cracks. If there are the tire is finished. Feel the rubber for flexibility, if the rubber does not wiggle, or if it breaks off, then it is time to move on to something new.

Q: I am coming to the end of my second set of Pirelli P Zero tires for my Jaguar XF Supercharged. The car has 33,000 km on it and is never driven between December and March. I am not an aggressive driver. I do like speed but average 120 km/h on highways and do take off ramps quickly. I do not do race or jump-start from stops.

The Pirelli?s are very expensive and when I went to my tire dealer (not car dealer) to replace the first set, he recommended only OEM tires. Now that I am looking into another replacement, I was wondering if there is a tire that would be less money but would provide the needed requirements for the car and may stand up to tire wear better? I have read reports that the Hankook Ventus 12 EVO K110 is a good replacement. My sizes are: front P255/35R20 97 Y, rear P285/30R20 99 Y.

A: Nice car! I would consider four tires for your car. In your sizing, there are only high-performance tires and they will all wear quickly, some more so than others.

The top dog in your group is the new Michelin Pilot Super Sport. It has all the latest Nano technology and is touted by Michelin to last longer than other tires in this group. The second choice is the new Bridgestone Potenza S-04 Pole Position. It also has Nano-tech engineering. It has self-renewing rubber, as one layer wears off the next layer down is grippier.

In the far less expensive line, the Hankook Ventus V-12 EVO is an excellent choice, just a bit less grip than the others and non-Nano, so wears a bit faster. Another economic choice that is not well known, but an excellent tire is the Sumitomo HTR Z III. Any of these will work on your car in the driving conditions you describe.

  • How to know when your tires have had the biscuit Jim Davidson points to worn tread on a tire. November 11, 2011. Nick Kozak/For the Toronto Star.

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