Colorado Traction Law tires, fitted in Denver

Colorado puts two tread depths in law, and one is three times the other.

C.R.S. 42-4-228(5)(c)(III) deems a tire unsafe below two thirty-seconds of an inch. That is the line you drive over on Colfax, on I-25 and in your own alley, all year. C.R.S. 42-4-106(5)(a)(I)(B) sets the Traction Law standard at three sixteenths of an inch, which is six thirty-seconds.

So a tire you may lawfully drive on in Denver in every month of the year can leave you short of the Traction Law standard on one stretch of I-70 for nine months of that same year.

Exactly where, and exactly when

The Traction Law is a travel restriction, not a general equipment rule. Under 42-4-106(5)(a)(I)(B), CDOT may restrict travel on a state highway in icy or snow-packed conditions unless the vehicle carries chains, an approved alternate traction device, or tires that meet the standard.

One stretch is written into the statute and does not wait for a storm. 42-4-106(5)(a)(I)(C) makes the restriction effective on Interstate 70 between milepost 133 at Dotsero and milepost 259 at Morrison, from September 1 through May 31 of each year. CDOT adds that it applies to every motorist not driving a commercial motor vehicle. Morrison sits roughly fifteen miles from downtown, so the corridor starts where the metro ends.

Nine months is longer than Denver's own winter. The National Weather Service puts the average first measurable snow in the Denver record at 19 October and the average last at 28 April, so the season opens about seven weeks before the city's first flake and closes about five weeks after its last. It is set for the mountains, which is why a Denver driver gets caught by it.

What changed in 2025, and where the texts diverge

Senate Bill 25-069, recorded as Chapter 196 and effective 6 August 2025, amended the four-wheel-drive clause of 42-4-106(5)(a)(I)(B). In the signed act, the words "and that are adequate for the conditions" were struck and a requirement was inserted that the tires carry a manufacturer's mountain-snowflake, "M&S", "M+S" or "M/S" marking, or be all-weather rated. Tread depth alone stopped being enough about three weeks before that season opened.

It amended only that clause. The all-wheel-drive clause still reads "all-wheel drive with tires that have a tread depth of at least three sixteenths of an inch and that are adequate for the conditions", with no marking requirement.

CDOT's guidance draws no such distinction. Its Passenger Vehicle Traction and Chain Laws page lists compliant configurations as AWD and 4WD vehicles on tires denoted with the mountain-snowflake icon or M+S or M/S with 3/16 inch of tread, and its November 2025 release says the law applies to all 4WD and AWD vehicles.

The enacted words and the agency summary are not identical on all-wheel drive, and we will not tell you the statute says something it does not. CDOT is the department that imposes the restriction and publishes what drivers are expected to carry. A marked tire at six thirty-seconds satisfies both readings, and that is the set we fit.

Above it sits the Chain Law

CDOT calls the passenger vehicle chain law the final safety measure before a highway closes. When it is in effect every vehicle needs chains or an approved alternate traction device, and no tire is good enough alone. CDOT publishes that device list in full: six products from four manufacturers.

Expect a fourth number quoted at you. The underlying rule, 2 CCR 601-14, still defines adequate tires as a minimum tread depth of 1/8 inch, and its editor's notes date the rule to 2012. The statute and CDOT both say three sixteenths. Work to three sixteenths.

We are not quoting a fine. CDOT's own pages give different penalty figures for the same offence, so we would rather give you nothing than a number to plan around.

Why this reaches so much of Denver

The only ranked drivetrain dataset we found is CarMax's analysis of its own 2004 to 2018 sales, published in 2019. Across the cities CarMax ranked, Denver came first at 72.23% of sales being four-wheel or all-wheel drive, with Colorado first among the ranked states at 72.64%. Read the limits with it: one retailer's used-car sales mix, not registrations, ending in 2018.

We supply and fit tires where the car is parked, matched to the door placard rather than to whatever is on the car now, and we measure the tread you have first. We do not sell used tires.

All-season, all-weather and winter tires explains what the markings mean, find your tire size covers reading the placard, what mobile tire replacement costs covers the money, and our Denver service area covers where we come. If you run two sets, tire storage keeps the off-season one out of the garage.

Our price: $145

A mobile puncture repair on one tire is $145. That is a price, not a range and not a starting point. It buys the trip out, the wheel off, the tire off the rim, an inspection of the inner liner, a plug and patch fitted to the tire industry standard, remounting, rebalancing, a TPMS reset where supported, and the pressure set to the placard. Nothing is added afterwards for the call-out. If the tire is beyond repair, you pay for the inspection and not for a repair that did not happen.

Questions people ask

• How much tread does the Traction Law want? Three sixteenths of an inch under C.R.S. 42-4-106(5)(a)(I)(B), which is six thirty-seconds. Colorado's unsafe-tire threshold in 42-4-228(5)(c)(III) is two thirty-seconds, so the traction standard is three times deeper.
• Do I need marked tires on an all-wheel-drive car? CDOT says yes, listing mountain-snowflake, M+S or M/S tires at 3/16 inch for AWD and 4WD alike. The statute is narrower: SB25-069 put the marking requirement into the four-wheel-drive clause only. A marked tire at 3/16 inch meets both readings.
• Is four-wheel drive on its own still enough? Not as the statute now reads. SB25-069 replaced "and that are adequate for the conditions" in that clause with a manufacturer marking or all-weather rating, effective 6 August 2025.
• How is the Chain Law different? Under the Traction Law a compliant tire is enough. Under the chain law, every vehicle needs chains or one of the six approved alternate traction devices whatever its tires.
• Are studded tires allowed? Yes, and C.R.S. 42-4-228(3) attaches no dates to them. The limits are on projection, no more than one sixteenth of an inch, and on vehicle type, single-tired vehicles rated up to three-quarters of a ton.