Cooper Discoverer Road+Trail AT: Specs, Sizes and Who It Suits

Written & researched by Dakota Reyes Recovery & Trail Systems Editor

Published Sep 29, 2026

Cooper

Cooper Discoverer Road+Trail AT

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Tire sizes, load ranges and speed ratings vary by listing — confirm with the seller for your exact year/trim and the size on your door-jamb placard.

Source: www.coopertire.com — manufacturer spec page, not Amazon.

Verified Size Chart (36 sizes)

What Cooper Built Into It

Cooper names four design features on the product page, described here as Cooper's claims:

• EnduraGuard design: an internal construction that helps the tire keep its shape on rough surfaces, for more even wear across the tread.
• Traction shoulders: the tread pattern extends more than 50% farther down the sidewall than on its predecessor, and the angled design is twice as thick, to give more grip on soft or uneven surfaces.
• Thick, rugged tread blocks: interlocking blocks for grip and control on uneven terrain.
• Winter Grip Technology: connected center tread lugs for stability and traction on snow.

The shoulder change is the most trail-focused item. When a tire is aired down on soft ground, more of the sidewall touches the terrain, so tread that reaches farther down the sidewall adds biting edges there. The other features are aimed at even wear and winter grip.

The Size Range, Row by Row

21 sizes are Standard Load and 15 are Extra Load, and none are LT-metric or flotation sizes. The chart runs from 225/70R15 and 235/75R15 through 265/70R17 and 275/65R18 up to 275/55R20 and 275/60R20, plus one 22-inch size, 285/45R22. Cooper's spec sheet also lists each size's load and dimensions:

The highest-rated size, 275/55R20 at 2,833 lb, is still a passenger tire. It carries less than an LT tire such as BFGoodrich's KO3 in LT265/70R17 Load Range E, which BFGoodrich rates at 3,415 lb. Several sizes, including 225/70R15, 255/70R16, 265/70R17 and 265/65R17, come with raised white letters; the rest are black sidewall.

Speed ratings are high for an all-terrain. 17 of the 36 sizes carry an H rating (130 mph on Goodyear's chart) or V rating (149 mph), and the rest are T-rated (118 mph). Every 15- and 16-inch size is T-rated; the H and V ratings are on 17-inch and larger sizes. Your door placard lists the minimum load index and speed rating for your vehicle.

Tread depth runs from 11/32" to 13/32", and 24 of the sizes sit at 13/32". The four 11/32" sizes are 235/65R18, 245/50R20, 255/55R20 and 265/50R20. Cooper's LT-only Discoverer Stronghold AT starts at 16/32", so the Road+Trail AT begins with noticeably less tread.

Snow Rating and Warranty in Context

Cooper states no size exclusions for the snowflake, so every size on the chart has passed the packed-snow traction test behind it: USTMA bulletin TISB 37 sets the bar at 10% better grip than a standard reference tire in ASTM F1805 testing. That test says nothing about ice, and a dedicated winter tire remains a different class of product.

The UTQG grade of 620-A-B on every size fits the wear-focused construction. Under 49 CFR 575.104, the treadwear number is relative: a tire graded 150 wears one and a half times as well on the government test course as one graded 100. Traction A means an adjusted wet braking coefficient above 0.47 on asphalt and 0.35 on concrete. Temperature B means the tire passed the 500 rpm stage of the laboratory heat test but not the 575 rpm stage required for an A.

How It Lines Up Against Similar Tires

Cooper's own Discoverer AT3 4S is the closest match on paper. It has the same 65,000 mi warranty, the same 620-A-B UTQG and the same SL/XL-only load ranges, and it's also 3PMSF rated. The AT3 4S runs a little deeper (12–14/32" (varies by size)) and is T-rated on nearly every size, while the Road+Trail AT carries H and V ratings on many of its larger sizes.

Falken's Wildpeak A/T Trail matches the 65,000 mi warranty and 3PMSF rating but has shallower tread (10–11/32" (varies by size)), and Falken says it's meant for crossovers, not pickups. The Nitto Nomad Grappler is also SL/XL-only and snow-rated, with a 60,000 mi warranty. If you need an LT load range for towing or a heavy camper, none of these fit. See the full all-terrain library, or use the tire finder to filter by size and load range.

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