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Weighing Summer vs. All-Season UHP Tires

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Swapping UHP summer (or, better said, “three-season”) tires for all-season UHP rubber is trading something you want for something you will probably never need.

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Consumers – and a shockingly high number of tire company sales staff – are under the mistaken belief that all-season tires offer better damp-road grip than summer tires.

The truth: All-season tires trade damp and dry grip in exchange for some (albeit limited) mobility on snowy roads and in well-below freezing temperatures.

It’s easy to see why people are confused. Those who live in California believe the seasons are Flood, Fire, Earthquake and Mudslide. Outdoors­men seasons are Fishing, Deer, Duck, and Turkey. Along the Gulf Coast, the seasons are Summer, Hurricane, Summer and Summer. Even those who regularly experience snow think Spring and Fall are included in “all seasons.” They’re wrong.

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There’s only one season when an all-season tire out-performs an otherwise equal summer tire: Winter. And not all of Winter. For those who live in Southern California and South Carolina, there are only a handful of days in the life of a tire that the driver wouldn’t be better off with summer, rather than all-season, tires.

Spring and early summer rainstorms send buyers to tire stores. That’s be­cause they’ve scared themselves half to death on a wet or damp road. Some will want to switch from their OE summer tires to all-season tires in the sadly mistaken belief that all-season tires offer better damp- and wet-road grip.

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Replacing summer tires with all-season tires in April or May is much like installing winter tires in March. By the time their best attribute is again needed, much of the “good” will have been worn away.

For the customer who lives where it regularly or occasionally snows, swapping from summer to all-season or winter in, say, November (and back to summer in March) is a good solution.

The reason summer tires beat all-season tires on damp roads is their stickier tread compound. The problem with such grippy rubber is that it gets hard when temperatures drop below freezing. It’s what some tire-nerds call “glass transition temperature.”

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At some temperature, all rubber starts acting more like a marble countertop than, well, rubber. That temperature varies with every tire, but even for summer tires, it’s well below freezing.

(A favorite phrase of tire company engineers is, “Well, that’s not EXACTLY correct.” In this case, they may point to a full-on race tire built 20 years ago for a long-defunct race series to prove their point. Engineers are like that. You just have to smile, nod your head and move on. Stay and they’ll soon be doing air math and your eyes will glaze over. After many man-hours, you’ll wind up with a compromise sentence: “…even for summer tires, it’s almost always well below freezing.”)

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Until now, we’ve been talking about the tread compound: the rubber. Extra credit for those who noticed the re­peated use of the phrase “damp-road grip.” There’s a huge difference bet­ween a tire’s grip on damp pavement and its ability to resist hydroplaning. A tire that offers almost no damp-road grip can be spectacular at coping with deep water. That’s because its tread pattern – the grooves and such – limit hydroplaning. Meanwhile, its long-lasting, all-season rubber provides little traction when the tire’s not hydro­planing.

I’ve experienced tires that were outstanding in deep water, but felt as if they were coated with Crisco on dry or damp roads. The opposite is true, too. If there was no standing water on the racetrack – or I could drive around the puddles – I’d rather have been on slick racing tires than on the best UHP all-season tire. And I’ve turned some dang fast laps on damp-but-drying tracks. There were even some deep puddles I had to remember to avoid.

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There are several UHP summer tires that offer both great dry/damp grip and are very resistant to hydroplaning. These usually feature long diagonal ribs. One problem with them is that the long – and thus flexible – diagonal ribs give some drivers the feeling that they’re about to lose control long, long before the tires start to slide.

It’s a huge challenge if the customer is complaining that his summer tires have no grip in the wet. A look at his tires should reveal the answer. If there’s less than 4/32nds inch of tread – especially on the rear – he’s almost certainly complaining about hydroplaning and not damp-road grip. Convincing him of that may not be possible.

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Another possibility is that the OE summer tires have been on the car for several years and no longer offer the Velcro-like grip they did when they were new. (Tires are like people: Even if they haven’t gone very far or done very much, they age to the point they can no longer do the job.)

Here’s something that can throw everything I’ve said out the window: There’s no government or industry specification for what is or isn’t an all-season tire.

Especially in the UHP segment, many manufacturers are stretching the definition almost to the breaking point. Who can blame them when consumers think “all-season” means “enhanced wet grip?” Such definition-stretching UHP all-season tires probably have enough snow grip to get you home if you get caught in an unexpected winter storm. But just barely.

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Just like all-wheel drive, the definition-stretching UHP all-season tires might only encourage people to drive when and where they shouldn’t.

I’ve spent enough space disrespecting UHP all-season tires. Now allow me to hammer summer tires. I’ve driven several that offer essentially no grip on a snowy road. One had so little grip that the car would barely back out of the garage. Another got stuck on a flat snow pad. Yet another caused me to fear crashing at 15 mph more than I did when testing an Indy car at 209 mph. A fourth had more traction in reverse than it did going forward.

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The first few were examples of glass transition temperature. With temperatures just above 0˚F, the rubber offered all the traction of Formica. I won’t guess why the one had more grip in reverse, as I’m not interested in arguing about it with tire engineers. So if someone is determined to drive a 911 in the snow, they’ll need at least all-season tires. If they live in Steamboat Springs or Billings, they’ll be a lot better off with winter tires.

Here’s your takeaway: Not all all-season UHP tires are bad, and not all summer tires are great. But all-season tires offer LESS damp-road grip than otherwise equal summer (or, better named, “three-season”) tires. Customers need to understand that before they disrespect their rides (and themselves) with a tire that may not do what they expect.

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