Affiliate disclosure: As an Amazon Associate, we earn from qualifying purchases, at no extra cost to you. We research rather than test, and commissions never change our rankings. This site is reader-supported: those commissions pay for hosting, research and keeping every guide up to date, so if a guide helped you, buying through our links is an easy way to support it. How we rank · Full disclosure
TL;DR
- Cooper has been a Goodyear brand since June 7, 2021; its warranties are now published on Goodyear's site.
- For work trucks, the Discoverer Stronghold AT (Load Range E on every size but one F) and AT3 XLT both carry 3PMSF and a 60,000-mile warranty.
- For SUVs and crossovers, the P-metric Road+Trail AT and AT3 4S both carry 3PMSF and a 65,000-mile warranty.
- The STT Pro mud-terrain has no 3PMSF badge and its product page lists only the Standard Limited Warranty and 45-day guarantee.
- Cooper's Standard Limited Warranty excludes racing and off-road use, road-hazard damage and tires altered with stud holes or extra siping.
Cooper became part of Goodyear when Goodyear completed its acquisition on June 7, 2021. Goodyear described the Cooper brand as a mid-tier line with particular strength in light truck and SUV tires. Six of its Discoverer tires are covered here, from P-metric crossover all-terrains to a dedicated mud-terrain.
At a Glance
| Tire | Aimed at | Sizes and load | 3PMSF | Mileage warranty |
|---|---|---|---|---|
| Discoverer Stronghold AT | Heavy-duty pickups, heavy loads, highway hauling | 28 sizes, Load Range E (one F) | Yes, all sizes | 60,000 mi |
| Discoverer AT3 XLT | Pickups that haul and tow | 33 rows, Load Range C to E | Yes | 60,000 mi |
| Discoverer Road+Trail AT | SUVs and crossovers | 36 P-metric sizes, SL and XL | Yes | 65,000 mi |
| Discoverer AT3 4S | SUVs and light trucks on P-metric sizes | 42 rows, SL and XL | Yes | 65,000 mi |
| Discoverer Rugged Trek (P-metric / LT) | Aggressive looks with on-road bias | 18 sizes across both listings | P-metric only | 60,000 / 55,000 mi |
| Discoverer STT Pro | Mud and rock | 47 rows, Load Range C to F | No | None shown |
Stronghold AT and AT3 XLT
The Discoverer AT3 XLT is built for pickups that haul and tow, with rugged traction shoulders Cooper says are exclusive to the XLT, Even Wear Arc Technology for balanced on-road wear, Whisper Grooves Technology for noise and stone ledges to eject gravel. The official spec sheet lists 33 rows across 15-20in wheels in Load Ranges C, D and E, 16-18/32in of tread, a 3PMSF badge and a 60,000-mile (90,000 km) warranty. The Discoverer Stronghold AT is built for heavy-duty pickups, heavy loads and long highway hauling: 28 sizes across 16-20in wheels, all Load Range E except the 35x12.50R20LT, which is an F, with 16-18/32in of tread, Cooper's Severe Snow Designation on all sizes and a 60,000-mile warranty.
Both are Load Range E in LT285/70R17, but they are not rated for the same weight. The AT3 XLT is 121/118 S, which Goodyear's load-index chart puts at 3,197 lb per tire. The Stronghold AT is 126 S, or 3,748 lb, which is 551 lb more per tire and 2,204 lb more across four. In LT275/70R18 the two match at 125 (3,638 lb). The load range letter sets the inflation class; the load index is the number to compare against the factory tire's.
Road+Trail AT and AT3 4S
The Discoverer Road+Trail AT and Discoverer AT3 4S are P-metric only (SL and XL, 15-22in wheels), both 3PMSF-badged with 65,000-mile warranties. The Road+Trail AT (36 sizes, 11-13/32in) uses EnduraGuard internal construction and traction shoulders Cooper says extend over 50% further down the sidewall than its predecessor. The AT3 4S (42 rows, 12-14/32in) uses a 5-rib tread with Adaptive-Traction, Snow-Groove and Aqua Vac Channel technologies. In 265/70R17 both are 115 T: 2,679 lb per tire and a 118 mph speed rating, the same load index as many half-ton trucks' factory P-metric tires. Both are UTQG-graded 620 A B in that size. The Road+Trail AT's sizes are rated H, T or V, up to 149 mph, while the AT3 4S is H or T; its 285/70R17 is 117 T, rated 2,833 lb per tire, with 14/32in of tread. Under 49 CFR 575.104, traction A means a wet-braking coefficient above 0.47 on asphalt and 0.35 on concrete, and temperature B means the tire passed the 500 rpm test stage but not the 575 rpm stage.
Discoverer Rugged Trek and Rugged Trek LT
The Discoverer Rugged Trek is Cooper's rugged-terrain tire, aimed at on-road driving with aggressive styling. It uses Earth Diggers shoulder scoops, Stable Trac micro-gauge siping and Whisper Grooves across 18 sizes (16-22in, 16-18.5/32in of tread). Cooper sells it as two listings with different coverage: the P-metric Rugged Trek carries the 3PMSF badge and a 60,000-mile warranty, while the Rugged Trek LT does not show the badge and carries 55,000 miles. The construction split is sharp. The P-metric version is T speed-rated (118 mph) with 16/32in of tread and a 600 A B grade; the LT version is Q-rated (99 mph) with 18.5/32in of tread and Load Range E or F. In 265/70R17, the P-metric is 116 XL (2,756 lb) and the LT is 121/118 E (3,197 lb). Two LT sizes are Load Range F: LT305/55R20 at 125/122 Q and 35x12.50R20LT at 125 Q, both 3,638 lb per tire.
Discoverer STT Pro
The Discoverer STT Pro is Cooper's extreme off-road mud-terrain, which Cooper describes as its most advanced, extreme and capable off-road tire to date. The named technologies are Stone Armor, Mud Slinger 2.0 trenches, Earth Diggers shoulder scoops, Rock Climber sidewall cleats and Armor-Tek3 construction. It spans 47 rows across 15-22in wheels, Load Ranges C-F and 18-22/32in of tread, with no 3PMSF badge. Its product page lists the Standard Limited Warranty and the 45-day guarantee but no mileage figure. Its speed ratings are low: Q (99 mph) on most sizes, and LT275/70R18 is rated P. Nineteen of its rows are flotation sizes, from 30x9.50R15LT to 40x13.50R17LT, and diameter doesn't predict capacity. The 40x13.50R17LT is a Load Range C at 121 Q (3,197 lb), the same rating as the Load Range E 35x12.50R20LT, while the 38x15.50R18LT and 38x15.50R20LT reach 128 Q (3,968 lb).
What Cooper's Warranty Covers Off-Road
Cooper's Standard Limited Warranty gives a free replacement if a replacement Cooper radial becomes unserviceable from a covered condition during the first 2/32in of tread wear. After that, the charge is the dealer's current price multiplied by the percentage of original tread worn. Coverage ends when the tire is worn to 2/32in or reaches 72 months from purchase, whichever comes first. The exclusions matter to off-road owners. The warranty does not cover road hazards (impacts, cuts, snags, punctures), "use in any racing or off road applications", or tires altered with extra siping, buffing, stud pin holes or re-grooving.
The Tread Wear warranty is a separate, prorated mileage warranty with no free-replacement period. It requires the original owner to rotate the tires at least every 8,000 miles and record it. The charge is miles delivered divided by miles warranted, times the current price of an equivalent Cooper tire. An AT3 XLT that wears out at 48,000 miles against its 60,000-mile warranty is replaced for 80% of that price. Other exclusions include commercial service (except select Discoverer HT3 sizes), ozone or weather checking on tires more than four years old, tires bought used, and tires worn unevenly by 2/32in or more between grooves. Goodyear also lists a Cooper 45-Day Satisfaction Guarantee on select tires, which lets the buyer exchange them within 45 days. To qualify for any of this coverage, the replacement tire must match or exceed the size, load index and speed rating the vehicle maker specifies, and it must stay on the vehicle it was first mounted on.
Cooper’s Lineup in This Library
6 Cooper models (All-Terrain, Mud-Terrain, Rugged-Terrain / Hybrid). Specs come from Cooper’s own spec pages; we don’t buy or test tires — see how we rank.
BFGoodrich, Goodyear, Michelin, Bridgestone, Falken, Toyo, Cooper, Nitto, Mickey Thompson, Yokohama, Hankook, General Tire and all other tire brand names referenced on this site are trademarks of their respective owners. 4x4 & Overlanding is an independent publication and is not affiliated with, sponsored or endorsed by any tire manufacturer.
Sources
- Goodyear — Goodyear Completes Acquisition of Cooper (June 7, 2021) — Cooper joining Goodyear on June 7, 2021, and Goodyear's description of the brand's light truck and SUV strength.
- Cooper — Discoverer AT3 XLT Tire Specification (PDF) — AT3 XLT features, 33 size rows, load indexes, load ranges, tread depths, 3PMSF and the 60,000-mile warranty.
- Cooper — Discoverer Stronghold AT product page — Stronghold AT sizes, Load Range E and F, load indexes, severe-snow designation and 60,000-mile warranty.
- Cooper — Discoverer Road+Trail AT specification (PDF) — Road+Trail AT sizes, EnduraGuard construction, shoulder claim, UTQG, 3PMSF and 65,000-mile warranty.
- Cooper — Discoverer AT3 4S Specification (PDF) — AT3 4S sizes, technologies, UTQG, 3PMSF and 65,000-mile warranty.
- Cooper — Discoverer Rugged Trek Tire Specification (PDF, both listings) — Rugged Trek and Rugged Trek LT sizes, speed ratings, load ranges, tread depths and UTQG.
- Cooper — Discoverer Rugged Trek LT product page — The LT listing's 55,000-mile warranty and absence of the 3PMSF badge.
- Cooper — Discoverer STT Pro product page — STT Pro technologies, Cooper's 'most advanced' description, and the warranties listed on its page.
- Cooper — Discoverer STT Pro Tire Specification (PDF) — STT Pro size rows, load ranges, speed ratings and tread depths.
- Goodyear — Cooper Standard Limited Warranty — Free replacement in the first 2/32in, prorated coverage to 72 months, and the exclusions for road hazards, off-road and racing use, and stud holes or added siping.
- Goodyear — Cooper Tread Wear Protection — The prorated mileage-warranty formula, the 8,000-mile rotation requirement and the size, load index and speed rating eligibility rule.
- Goodyear — Tire Warranty overview — The Cooper 45-Day Satisfaction Guarantee on select tires.
- Goodyear — Load Index and Speed Rating — Load-index conversions up to 120 and the speed-symbol chart.
- Goodyear Canada — Tire Load Index chart — Load-index conversions above 120 used in the AT3 XLT vs Stronghold AT comparison.
- 49 CFR 575.104 — Uniform Tire Quality Grading Standards (LII / Cornell) — What UTQG traction grade A and temperature grade B mean.