Off-RoadX Trail Report #5 - Your 4WD Isn't Enough

5 days ago

7 min read

THE OFF-ROADX TRAIL REPORT #5

YOUR 4WD ISN’T ENOUGH

COLORADO’S TRACTION LAW IS BACK

You have four-wheel drive.

You have big tires.

You have enough suspension travel to make the average commuter vehicle feel personally inadequate.

You’re ready for Colorado winter—right?

Maybe.

Colorado’s seasonal Traction Law returned September 1, and one of the most important changes is something many truck, Jeep and SUV owners could easily miss:

Four-wheel drive or all-wheel drive alone is no longer enough.

Your tires now matter just as much as your drivetrain.

Let’s break down what the law requires, where it applies and what you need to check before your next trip into the mountains.

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WHEN AND WHERE DOES THE LAW APPLY?

Colorado’s Passenger Vehicle Traction Law is automatically in effect every year from September 1 through May 31 on the I-70 mountain corridor between:

Morrison—milepost 259

and

Dotsero—milepost 133

That means the seasonal requirement covers approximately 126 miles of I-70 through the mountains, including travel toward communities such as Idaho Springs, Georgetown, Silverthorne, Frisco, Vail and Avon.

CDOT can also activate traction and chain restrictions on any state highway whenever weather and road conditions require them.

That includes highways leading to many of the places off-roaders, campers, skiers and mountain travelers visit throughout the winter.

It can be sunny in Castle Rock, raining in Denver and snowing sideways on a mountain pass.

Colorado weather does not review your travel itinerary before making decisions.

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FOUR-WHEEL DRIVE IS NO LONGER A COMPLETE ANSWER

Colorado updated the Passenger Vehicle Traction Law in fall 2025.

Under the current requirements, an AWD or 4WD vehicle must have qualifying tires with at least 3/16 inch of tread depth.

Qualifying tires include:

Winter tires displaying the three-peak mountain snowflake symbol

Mud-and-snow tires marked M+S, M/S or M&S

Tires carrying an all-weather rating from the manufacturer

If your AWD or 4WD vehicle does not meet those tire and tread requirements, you must use chains or an approved alternative traction device on at least two drive tires when required.

Translation:

The transfer-case selector is not a legal hall pass.

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HOW MUCH TREAD IS 3/16 INCH?

Three-sixteenths of an inch is the same as:

6/32 inch

or approximately:

4.8 millimeters

That requirement applies even to AWD and 4WD vehicles.

A tire can look aggressive from five feet away and still be worn below the legal minimum. Uneven wear can also leave one shoulder compliant while another portion of the same tire is not.

Use an actual tread-depth gauge and check:

Every tire

More than one groove

Multiple locations around each tire

Both the inner and outer portions of the tread

Don’t rely exclusively on the wear bars. Standard wear bars commonly indicate approximately 2/32 inch—far below Colorado’s 6/32-inch Traction Law requirement.

If the tire is approaching 6/32 now, it may not remain compliant through the entire winter.

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M+S AND THE MOUNTAIN SNOWFLAKE ARE NOT THE SAME

Both markings can qualify under Colorado’s law when the tire has sufficient tread, but they do not represent the same level of testing.

M+S—or mud and snow—is generally a manufacturer designation based largely on tread-pattern characteristics.

The three-peak mountain snowflake, commonly abbreviated 3PMSF, indicates that the tire met a standardized acceleration-traction test in severe snow conditions.

Many all-terrain tires carry both markings.

Some carry only M+S.

A tire can therefore be legally acceptable while another tire may still deliver better real-world winter performance.

Legal compliance is the minimum—not necessarily the ideal setup for the conditions you plan to encounter.

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“ALL-SEASON” DOESN’T AUTOMATICALLY MEAN “ALL-WEATHER”

These terms sound nearly identical.

They aren’t.

CDOT identifies manufacturer-rated all-weather tires as qualifying equipment. A basic all-season tire does not automatically qualify merely because its name suggests it works throughout the year.

Look at the tire itself.

Search for:

• The three-peak mountain snowflake

• M+S

• M/S

• M&S

• A documented all-weather rating from the manufacturer

If you cannot find a qualifying designation, do not assume the tire complies.

Marketing copy is not a tire rating.

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WHAT ABOUT TWO-WHEEL-DRIVE VEHICLES?

Two-wheel-drive vehicles—including front-wheel-drive cars and rear-wheel-drive trucks—face different requirements under the updated law.

Current Colorado State Patrol guidance says 2WD vehicles traveling the I-70 mountain corridor must carry tire chains or an approved alternative traction device from September 1 through May 31, regardless of the tires installed.

When an active restriction requires those devices to be installed, they must be placed on at least two drive tires before proceeding.

For a front-wheel-drive vehicle, that generally means the front tires.

For a rear-wheel-drive vehicle, that generally means the rear tires.

Always follow the vehicle manufacturer’s instructions. Some vehicles have limited clearance around the tire, suspension or brake components and may restrict the type of chain or traction device that can safely be used.

Owning chains that destroy a brake line is technically preparation.

It is not particularly good preparation.

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TRACTION LAW AND CHAIN LAW ARE NOT THE SAME

Colorado has two separate levels affecting passenger vehicles.

PASSENGER VEHICLE TRACTION LAW

This is the more common restriction.

AWD and 4WD vehicles may proceed with qualifying tires and at least 3/16-inch tread depth. Vehicles that do not meet the requirements need chains or an approved alternative traction device.

PASSENGER VEHICLE CHAIN LAW

This is the most restrictive passenger-vehicle requirement and is generally the final safety step before CDOT closes the highway.

When the Passenger Vehicle Chain Law is active, every passenger vehicle must use chains or an approved alternative traction device.

Yes, that includes:

• Four-wheel-drive trucks

• AWD crossovers

• Jeeps

• Broncos

• Subarus

• Vehicles wearing tires with mountain snowflakes

• The person confidently explaining that they have driven in Colorado for 30 years

Under the Passenger Vehicle Chain Law, AWD and good tires are no longer sufficient by themselves.

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WHAT IS AN ALTERNATIVE TRACTION DEVICE?

Colorado permits certain approved alternatives to traditional metal chains.

These may include approved products such as:

• Tire socks

• Cable-style devices

• Other traction systems appearing on CDOT’s approved-products list

Not every product advertised online as a “chain alternative” is approved in Colorado.

Before purchasing one:

Check CDOT’s current approved-products list

Confirm the correct size for your tire

Verify compatibility with your vehicle

Read the installation instructions

Practice installing it before winter

The side of I-70 during a snowstorm is a terrible classroom.

Open the package at home. Make sure every part is present.

Confirm that the device actually fits over your tires and clears the surrounding components.

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OFF-ROAD TIRES AREN’T AUTOMATICALLY WINTER TIRES

A large all-terrain or mud-terrain tire may look unstoppable.

That doesn’t automatically make it excellent on packed snow or ice.

Large tread blocks can work well in deep snow and loose terrain, but winter performance is also affected by:

• Rubber compound

• Temperature flexibility

• Siping

• Tread-block design

• Tire pressure

• Vehicle weight

• Tread depth

• Road surface

Mud performance and ice performance are not the same thing.

Check the tire’s markings and specifications rather than assuming its appearance tells the entire story.

Your 37-inch mud tire may be highly offended by this information.

The ice remains unmoved.

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4WD HELPS YOU GO—TIRES HELP YOU STOP

Four-wheel drive can help distribute engine power and improve acceleration in slippery conditions.

It does not create additional tire grip during braking.

Every vehicle still relies on four small contact patches to:

• Accelerate

• Turn

• Brake

• Maintain stability

That is why tire type, tread depth and driving behavior remain critical even in a highly capable 4x4.

A vehicle that accelerates confidently can create a dangerous illusion that the road has more traction than it actually does.

Test your braking gently at a low speed when it is safe to do so.

Increase following distance and make every steering, throttle and braking input smoother than normal.

Capability should create confidence.

It should not create surprise.

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WHAT HAPPENS IF YOU DON’T COMPLY?

CDOT’s current Passenger Vehicle Traction and Chain Law page lists:

• A $100 fine plus a $33 surcharge for noncompliance

• A $500 fine plus a $157 surcharge when noncompliance results in the closure of a travel lane in one or more directions

Those costs do not include towing, vehicle damage, lost time or the emotional experience of realizing thousands of people are now stopped behind you.

More importantly, an unprepared vehicle can cause a crash, strand its occupants or prevent emergency vehicles from reaching someone else.

The law establishes the minimum equipment.

The goal is getting everyone through the mountains safely.

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HOW WILL YOU KNOW A RESTRICTION IS ACTIVE?

CDOT communicates active restrictions through:

• Electronic highway message signs

• COtrip.org

• The COtrip Planner app

• Traffic and roadway-condition alerts

• CDOT social-media updates

• Local news and weather reports

Check conditions before departure and continue monitoring them during the trip.

If a sign says traction devices are required, find a safe designated location to install them before proceeding.

Do not stop in an active travel lane.

Do not attempt to install chains where passing traffic cannot see you.

And do not continue simply because the road “doesn’t look that bad yet.”

The sign applies before your personal assessment of the snow reaches a two-thirds majority.

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THE OFF-ROADX WINTER-READINESS CHECK

Before heading into Colorado’s mountains:

Confirm whether the vehicle is 2WD, AWD or 4WD.

Inspect every tire for M+S, 3PMSF or an approved all-weather rating.

Measure tread depth with a proper gauge.

Confirm that each installed tire has at least 6/32 inch of tread.

Carry chains or an approved traction device when required.

Verify that the device fits your exact tire size.

Practice installing it somewhere warm, dry and safe.

Check the owner’s manual for chain-clearance restrictions.

Pack gloves, a kneeling pad, flashlight and reflective clothing.

Check COtrip immediately before leaving.

Your chain kit should not be a sealed box you bought three years ago and have been emotionally supporting ever since.

Open it.

Inspect it.

Practice with it.

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OFF-ROADX CAN HELP

Not sure whether your tires qualify?

We can help inspect the tire markings, measure the remaining tread and determine whether your current setup is ready for Colorado winter.

If it’s time for new tires, Off-RoadX can help you select, order, mount and balance the right tires for your car, SUV, truck or off-road vehicle.

Because the best time to discover your tires don’t meet the Traction Law is in the shop. Not beneath a flashing sign on I-70.

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THE OFF-ROADX BOTTOM LINE

Colorado’s Traction Law is back.

From September 1 through May 31, the seasonal requirements apply on I-70 between Morrison and Dotsero. CDOT can also activate traction restrictions on any state highway when conditions require them.

The most important things to remember are:

AWD and 4WD alone are not enough

Qualifying tires need at least 3/16-inch tread

All-season and all-weather are not automatically the same

Two-wheel-drive vehicles should carry approved traction equipment

A Passenger Vehicle Chain Law applies to everyone—including 4x4s

Check COtrip before driving into the mountains

Four-wheel drive is an incredible tool.

Good tires are what connect that tool to the road.

Check the rating.

Measure the tread.

Carry the equipment.