The M&S/All-Season Tire Myth: Why Closed Shoulders Kill Winter Traction

By Joe Saunders | ALL TIRE Elk River, MN

A Tire Shop Truth Nobody’s Talking About

Walk into any big-box tire retailer in Minnesota and you’ll see racks loaded with tires labeled “Mud & Snow” or “All Season.” Most customers grab them without a second thought. They think that M&S badge means winter traction. What they don’t know—and what most tire shops won’t tell them—is that many of these tires are fundamentally designed wrong for the job they’re expected to do in Minnesota winters.

After 35 years in this business, I’ve watched the tire industry get better at a lot of things. What I’ve also watched is the rise of a marketing trick that’s costing customers both safety and money. It’s the contradiction between the Mud & Snow rating, the All Season rating, and something called a “closed shoulder” design.

Manufacturers are slapping both of these designations on closed-shoulder tires and selling them in Minnesota as if they deliver winter and wet-weather performance, when the engineering actually undermines it. And once you understand it, you’ll never look at tires the same way again.

What Open Shoulders Actually Do

Let’s start with the basics. A tire’s tread isn’t just there to grip dry pavement. In winter, it’s also responsible for moving moisture, slush, snow, water, and ice crystals out from under the contact patch. If that moisture stays trapped under the tire, you get hydroplaning—or slipping and sliding.

The tire floats on the moisture instead of gripping the road. That’s how you lose traction and end up in a ditch on I-94.

The shoulder of the tire—that’s the area where the tread grooves meet the sidewall—plays a critical role in this evacuation process. When you have open shoulders, those grooves typically extend all the way from center tread to the edge of the tire, creating channels that force slush, snow, and water to escape outward and away from the contact patch. Think of it like gutters directing water off your roof. The water doesn’t sit on the surface; it gets moved somewhere else.

A closed shoulder, on the other hand, is a smooth, uninterrupted section of tread at the tire’s edge. The grooves stop before they reach the outer edge. Closed shoulders offer some benefits in other areas—like better fuel efficiency, longer tread life, sometimes a quieter ride, and improved tread stability/handling. They’re great for highway cruising, dry conditions, performance cars used only in summer, and for customers in warm climates who never deal with moisture or snow on the road.

A CLOSED SHOULDER TIRE (ABOVE PIC)

AN OPEN SHOULDER TIRE (ABOVE PIC)

But here’s where it gets dangerous: A closed shoulder traps moisture instead of evacuating it. The weight of the vehicle pushes down on the tread, but without those open channels at the shoulder, the slush and water have nowhere to go. They get held under the tire longer, increasing the risk of hydroplaning and reducing winter traction. It’s the opposite of what you want when you’re driving on Minnesota’s snow and slush.

What “Mud & Snow” Is Supposed to Mean

The “Mud & Snow” or “M+S” designation isn’t a suggestion. It’s supposed to indicate that a tire gets winter traction better than a non-M&S or all-season tire. An M&S tire will be better in Minnesota when it has:

• Deeper tread depth
• More openings and sipes (small cuts in the tread blocks) for better grip on snow, slush and ice
• A tread design optimized to shed snow, slush and water

The whole point of the M&S rating is winter performance. It’s a sign that the tire will handle Minnesota winter conditions better than an all-season or summer-only tire. It means the tire has been engineered for snow and slush traction. or like it actually says MUD + SNOW

What About All Season?

Now, you might think all-season tires get a pass here. They don’t. An all-season tire is supposed to be a compromise with decent performance in rain, acceptable in light snow, and good in dry conditions. The keyword is “compromise,” not “ignore winter.”

When you put a closed shoulder on an all-season tire, you’re taking away its ability to handle rain and slush effectively. You’re making it worse at its fundamental job—to perform adequately across different weather conditions.

In Minnesota, where we get rain, slush, snow, and freeze-thaw cycles, an all-season tire with a closed shoulder is just as problematic as an M&S tire with a closed shoulder. The closed shoulder traps moisture in wet conditions just like it does in snowy conditions. The physics don’t change.

So when you slap an M&S or all-season rating on a tire with a closed shoulder, you’re making a promise you can’t keep.

The Contradiction

This is where it stops being an engineering oversight and starts looking like a marketing strategy.

A tire with a closed shoulder and an M&S rating is a fundamental contradiction. You’re putting a premium winter rating on a design that undermines the basic physics of winter traction. It doesn’t make sense from an engineering perspective. But it makes perfect sense from a business perspective.

Why? Because closed-shoulder tires sell more tires across more markets. A closed shoulder tire performs better in dry conditions and delivers the fuel efficiency and longevity that appeal to drivers in warm states and dry climates. Manufacturers use the same tire globally, but they market it differently depending on the region.

In Arizona or New Mexico, they sell it as an all-season tire with a story that sounds great: “Excellent year-round performance in our climate with better fuel economy.” In Minnesota, they sell the same exact tire as an all-season or M&S tire with a completely different story: “All-weather capability for Minnesota winters.”

In Albuquerque, where it rarely rains and never snows, a closed-shoulder design actually makes sense. But in Minnesota, where we get rain, slush, snow, and constant moisture on the road, that same closed-shoulder design is a liability.

The closed shoulder works fine in Albuquerque’s climate. It doesn’t work in Minnesota’s climate. Yet manufacturers sell it as if the designation means the same thing everywhere.

That’s the marketing trick: charging M&S or all-season prices and making promises about all-season capability on a tire that isn’t actually optimized for Minnesota conditions. It’s the tire industry equivalent of selling a four-door car with a golf club included and calling it a sports car. They’re using the exact same marketing in snow country.

Why It Matters in Minnesota

Minnesota winters aren’t all deep snow. They’re a complex mix of conditions that change day by day, even hour by hour. You get:

• Wet, slushy snow when it first falls
• Refrozen slush and ice ruts on highways
• Freezing rain over packed snow
• The thaw-and-freeze cycle that creates black ice
• Piles of slush in tire tracks where moisture accumulates

In every single one of those scenarios, you need a tire that can move moisture out from under the contact patch. Open shoulders do that. Closed shoulders trap it. This isn’t theoretical—it’s physics in action every day on I-94, Highway 10, and every county road or residential street in the Twin Cities.

We’ve been putting winter tires on customer vehicles for decades. The difference between a tire with open shoulders and one with closed shoulders in Minnesota slush isn’t subtle. Drivers notice it. They feel the difference in how the car responds in slush, how confident they feel maintaining traction on the highway, and whether they can navigate a slick road without losing grip.

Many customers have told us the difference literally saved them from the ditch or an accident.

A customer rolling on M&S-rated or all-season-rated closed-shoulder tires, thinking they’ve got good winter and wet-weather protection? They’re taking more risk than they realize. And they’re doing it because they trusted a marketing label or a naïve tire salesperson over actual engineering.

Whether it says “Mud & Snow” or “All Season,” a closed shoulder undermines winter and rain traction in Minnesota.

The Big-Box Problem: Where Customers Can Get It Wrong (Or Get Sold Wrong)

Here’s something we see consistently at All Tire: customers come in frustrated because they just bought new M&S or all-season tires from Discount Tire, Tires Plus, Walmart, or Costco, and they’re disappointed with the traction they’re getting in snow, slush, and rain.

Many are frustrated, stating “my vehicle is horrible in the winter.” They went to those big-box retailers, asked for a Mud & Snow or all-season tire expecting reasonable winter and wet-weather performance, paid good money, and ended up with a tire that doesn’t deliver the traction they assumed that designation would provide.

Why does this happen? Because the big-box retailers are moving volume, not matching tires to conditions. They’re pushing whatever tire makes the most margin and fits their inventory. They’re not spending time explaining the difference between an open-shoulder design and a closed-shoulder design.

Most of their sales staff probably don’t even understand it themselves. And honestly, they probably don’t care, as the manufacturer’s marketing is doing the heavy lifting for them.

A customer walks in and says, “I need an all-season tire that handles rain and light snow.” Or: “I need a Mud & Snow tire for winter driving.” The staff member grabs a tire with a closed shoulder and the appropriate label, sells it on price and brand recognition, and sends them out the door.

Nobody talks about tread design. Nobody mentions that the closed shoulder is going to trap moisture instead of evacuating it. Nobody says, “Hey, this tire is optimized for fuel economy in dry climates. If you really want Minnesota-appropriate traction, here’s what you should be looking at.”

Then the customer drives home, experiences disappointing traction in Minnesota slush, rain, or snow, and feels like they got ripped off or blames it on their car or truck. Technically, they didn’t get ripped off because the tire is cheap or defective—they got a tire that doesn’t match what they actually need.

The M&S or all-season badge promised adequate snow/slush and wet-weather performance. The closed-shoulder design undermines that promise. But the big-box retailer doesn’t care, because the transaction is already done.

When these frustrated customers show up at our shop later, they’re not looking to blame the retailer—they just want to know why their new tires aren’t working. And when we explain the open-shoulder versus closed-shoulder issue, they get it immediately. They understand the physics. And they realize they should have asked that question before they bought.

This is exactly the kind of thing a good tire shop should be there to catch. Not to criticize the big-box retailer, but to make sure you’re getting actual winter performance, not just a winter label.

It’s Not Just Marketing—It’s a Safety Issue

We’re not talking about minor performance differences. We’re talking about traction loss in exactly the conditions where you need traction most. Winter accidents happen when drivers lose grip they thought they had. They happen when a tire that’s supposed to be rated for snow conditions actually isn’t optimized for winter conditions.

Every time we’ve recommended an open-shoulder tire to a customer who was considering a closed-shoulder M&S option, we’ve done it because we believe it will keep them safer. It’s that simple. We’re not trying to up-sell them to a premium product. We’re trying to make sure they’re actually getting what they’re paying for.

When a customer comes into All Tire and asks for winter tires, we ask the right questions. We look at their driving patterns, their vehicle, and the actual conditions they’ll face. And we steer them toward tires with open shoulders, even if they’re the same brand and price point as the closed-shoulder options next to them. Because we know the difference it makes.

We consistently see customers come back in the spring and tell us about the improved grip, the better handling on slush, and the confidence they felt driving in February snow. And we know that the alternative—a closed-shoulder M&S tire—would have left them sliding.

What You Should Do

If you’re buying winter tires for a Minnesota vehicle, don’t just look at the label. Look at the actual tread design. Check if those grooves extend all the way to the shoulder or if they stop short. Ask your tire shop about it.

Most shops that know what they’re doing will understand the question. Some might not have thought about it, but it’s worth asking anyway.

And if a shop is trying to sell you an M&S or all-season tire with a closed shoulder without mentioning the trade-off? That’s a red flag. Either they don’t understand tire design, or they’re more interested in moving inventory than matching you with the right product.

The question isn’t whether it says M&S or all-season. The question is whether it has open shoulders. In Minnesota, that matters more than the label.

The Bottom Line

At Joe’s All Tire Elk River, we believe in being honest about what tires will and won’t work in our changing Minnesota weather. We’ve built our reputation on understanding tire technology and matching it to real-world driving conditions. Winter in Minnesota is serious, and your safety depends on it. That’s not something we take lightly, and it’s not something we’ll compromise on for a sale.

For a deeper technical breakdown of tire shoulder design and how it impacts performance, check out our Knowledge Center at www.joesalltire.com/knowledge-center/

If you want to talk about winter tires—the real story, not the marketing version—come see us. We’re at 20300 Auburn Street NW in Elk River, or call us at 763-241-1874. We’ll take the time to make sure you’ve got the right tires for Minnesota winter. No shortcuts, no marketing tricks, just the honest truth about what will keep you safe on the road.

Because your safety is more important than a manufacturer’s profit margin.