Ask a Trooper

Question: How do you determine if your tires are unsafe for winter driving?

Answer: Over the years, I have investigated numerous crashes where worn tires were a contributing factor. Tires with inadequate tread depth may cause your vehicle to skid or slide out of control on a slippery or wet road surface. It is important to remember that unsafe tires can hydroplane on both wet and snow covered roadways. When losing control of your vehicle, you can easily go off the road and into the ditch, or into oncoming traffic, possibly causing serious injury or death.

According to Minnesota State Statute 169.723 a tire shall be considered unsafe if it has:

(1) Any part of the ply or cord exposed; or

(2) Any bump, bulge or separation; or

(3) a tread design depth of less than 2/32 (1/16) of an inch measured in the tread groove nearest the

center of the tire at three locations equally spaced around the circumference of the tire, exclusive of tie

bars or for those tires with tread wear indicators; or

(4) Been worn to the level of the tread wear indicators in any two tread grooves at three locations; or

(5) A marking “not for highway use,” or “for racing purposes only,” or “unsafe for highway use;” or

(6) Tread or sidewall cracks, cuts or snags deep enough to expose the body cords.

My best advice is to keep an eye on your tires. Check your tire pressure often as it can be as much as 50% underinflated before it is visibly noticeable. Use a pressure gauge to check each tire and know what your pressure should be. Routine maintenance is good insurance; rotate, balance and be sure that your vehicle is correctly aligned, according to your vehicle owner’s manual.

Taking a few seconds to walk around your vehicle before leaving for your destination can pay off, potentially keeping you from getting into a crash. Speaking from personal and professional experience, the “snow” tires I run at this time of the year have made all the difference throughout some of the deepest snow and treacherous conditions. I would not want to be without them. Having a set of tires with good, legal tread depth will increase your chances of not being involved in a crash, especially when the weather and road conditions become poor.


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