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Cooper Discoverer STT PRO vs Dunlop Grandtrek AT20 — Compared

Relative Score (0–100): the weighted average of the categories below, each 60% road tests and 40% owner reviews (comfort 40/60). Based on 0 + 0 road tests and 421 + 57 owner reviews. How we score

Discoverer STT PRO is ahead, 63–44

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Category by category

Relative Score per category, 0–100. Open “Why this score” for the tests and owner ratings behind it.

  1. 65

    Dry

    Discoverer STT PRO +24
    41
    Why this score
    SourceDiscoverer STT PROGrandtrek AT20
    Professional tests (TWG score)≈ 66 (est.)≈ 51 (est.)
    Reviews found online6327

    Discoverer STT PRO: 60% × 65.8 (est.) + 40% × 62.6 = 65

    Grandtrek AT20: 60% × 50.9 (est.) + 40% × 27.2 = 41

    No road tests of dry for Discoverer STT PRO. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.42).

    No road tests of dry for Grandtrek AT20. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.42).

  2. 68

    Wet

    Discoverer STT PRO +26
    42
    Why this score
    SourceDiscoverer STT PROGrandtrek AT20
    Professional tests (TWG score)≈ 68 (est.)≈ 49 (est.)
    Reviews found online6732

    Discoverer STT PRO: 60% × 68.5 (est.) + 40% × 66.6 = 68

    Grandtrek AT20: 60% × 49.1 (est.) + 40% × 31.5 = 42

    No road tests of wet for Discoverer STT PRO. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.55).

    No road tests of wet for Grandtrek AT20. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.55).

  3. 67

    Snow

    Discoverer STT PRO +18
    49
    Why this score
    SourceDiscoverer STT PROGrandtrek AT20
    Professional tests (TWG score)≈ 69 (est.)≈ 58 (est.)
    Reviews found online6536

    Discoverer STT PRO: 60% × 68.5 (est.) + 40% × 64.8 = 67

    Grandtrek AT20: 60% × 57.8 (est.) + 40% × 36.2 = 49

    No road tests of snow for Discoverer STT PRO. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.37).

    No road tests of snow for Grandtrek AT20. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.37).

  4. 55

    Comfort

    Discoverer STT PRO +12
    43
    Why this score
    SourceDiscoverer STT PROGrandtrek AT20
    Professional tests (TWG score)≈ 65 (est.)≈ 62 (est.)
    Reviews found online4830

    Discoverer STT PRO: 40% × 65.3 (est.) + 60% × 48.1 = 55

    Grandtrek AT20: 40% × 62 (est.) + 60% × 30 = 43

    No road tests of comfort for Discoverer STT PRO or Grandtrek AT20. The test half is the tested tires’ average (69): owners’ comfort ratings barely follow the road tests.

  5. 53

    Noise

    Grandtrek AT20 +3
    56
    Why this score
    SourceDiscoverer STT PROGrandtrek AT20
    Professional tests (TWG score)≈ 67 (est.)≈ 67 (est.)
    Reviews found online3240

    Discoverer STT PRO: 60% × 66.6 (est.) + 40% × 32.1 = 53

    Grandtrek AT20: 60% × 66.6 (est.) + 40% × 39.6 = 56

    No road tests of noise for Discoverer STT PRO or Grandtrek AT20. The test half is the tested tires’ average (67): owners’ noise ratings barely follow the road tests.

  6. 62

    Treadwear

    Discoverer STT PRO +11
    51
    Why this score
    SourceDiscoverer STT PROGrandtrek AT20
    Professional tests (TWG score)≈ 64 (est.)≈ 57 (est.)
    Reviews found online5941

    Discoverer STT PRO: 60% × 63.7 (est.) + 40% × 59.3 = 62

    Grandtrek AT20: 60% × 57.4 (est.) + 40% × 41.2 = 51

    No road tests of treadwear for Discoverer STT PRO. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.35).

    No road tests of treadwear for Grandtrek AT20. The test half is estimated from the owner ratings, as far as owners and testers agree (correlation 0.35).

  7. 52

    Handling (owners)

    Discoverer STT PRO +19
    33
    Why this score
    SourceDiscoverer STT PROGrandtrek AT20
    Reviews found online5233
Scores at a glance
CategoryCooper Discoverer STT PRODunlop Grandtrek AT20
Relative Score 63 44
Dry 65 41
Wet 68 42
Snow 67 49
Comfort 55 43
Noise 53 56
Treadwear 62 51
Handling (owners) 52 33

Higher is better. The Relative Score follows your weights below; category scores do not change.

Weight the categories that matter to you

Wet grip starts at “Important”. Treadwear starts at “Neutral” here: road tests measured it for at most one of the two tires, so it rests on owner reviews. Move the sliders and the scores update instantly.

Important
NotLessNeutralImportantMost
Important
NotLessNeutralImportantMost
Neutral
NotLessNeutralImportantMost
Less important
NotLessNeutralImportantMost
Less important
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Neutral
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Recomputed
Headline score
± 7

Discoverer STT PRO

± 7

Grandtrek AT20

Pros, cons & observations

Themes extracted from owner reviews found online — not the opinion of TireWheelGuide.

Tire A Discoverer STT PRO

Pros

  • Outstanding off-road traction in mud, rocks, and dirt
  • Surprisingly low road noise and smooth ride for a mud-terrain tire
  • Aggressive and appealing visual design with tough sidewalls

Cons

  • Can be difficult to balance properly, leading to vibrations for some users
  • Faster tread wear reported by a subset of drivers under heavy use
  • Reduced traction in specific conditions like deep sand or packed snow/ice
All owner themes in the Discoverer STT PRO review

Tire B Grandtrek AT20

Pros

  • Exceptional tread life and high mileage capability (often exceeding 40,000 to 60,000+ miles)
  • Comfortable, smooth, and quiet ride on tarmac and highways
  • Good stability and predictable handling in dry, warm weather conditions

Cons

  • Extremely poor and potentially unsafe traction on wet roads, leading to sliding and long braking distances
  • Unreliable or hazardous performance in winter conditions like snow and ice
  • Subpar off-road capabilities, including low puncture resistance on gravel and poor traction in mud or sand
All owner themes in the Grandtrek AT20 review

What real owners are saying

From Reddit, forums and review threads. Not part of our score

Tire A

Cooper Discoverer STT PRO

Positive

Community members widely praise the Cooper Discoverer STT PRO for its exceptional off-road traction, towing capability, and dependable handling in mud, rain, and snow. While users note it balances well and rides comfortably for a mud-terrain tire, the most common criticisms involve pavement road noise that increases with wear and concerns regarding tread life on heavy trucks.

duramaxforum.com ·1 upvote ·2015-09-14

“was running 65 front & 75 rear, will lower when not towing heavy, Sent from AutoGuide.com Free App”
subaruoutback.org ·2023-09-21

“I have never been let down by Cooper Discoverer STT PRO or BFGoodrich KO2 off road tires. I love the traction the Cooper STT PRO give me off-roading in the desert. I drove on KO2 from the 2018 until I got my STT PRO. I had Firestone’s as original equipment on a couple different vehicles and never had so many flats (on road or off road).”
r/FJCruiser ·2 upvotes ·2026-03-21

“I thought I'd throw my two cents in! I put 5 Cooper Discoverer STT Pro tires on my 2015 Nissan Xterra Pro-4 X in 2021. It cannot be overstated - I LOVE these tires! They're great in dry conditions, they're great in the rain, they're great in the snow, they're great on ice - they even drove over a frozen iceberg in my driveway during a winter emergency as though it wasn't even there. There's a little bit of road noise, but nothing terrible. You can definitely "feel" them when you're driving - but I kind of like that. My truck sits outside during all kinds of Ohio weather, and they don't appear to be cracking/dry rotting quite yet. It will technically be "due" for me to get a new set of tires next year. Without a doubt, I'm getting another set of these!! Happy trails, all!”
Top themes
#off-road traction#highway road noise#mud and snow performance#tread wear life#heavy truck towing#balancing and ride quality

Based on 38 community posts

Tire B

Dunlop Grandtrek AT20

We haven't collected enough community discussion about this tire yet.

Specs side by side

Attribute A · Cooper Discoverer STT PRO B · Dunlop Grandtrek AT20
CategoryMud-Terrain tireAll-Terrain tire
Vehicle typeSUV and 4x4SUV and 4x4
Sizes available239
Rim diameters16″ – 20″15″ – 18″
Tread depth18 - 22/32″—
SidewallBlack Side Wall - Raised White LetteringBlackwall
Max pressure35 - 80 psi—
Sizes in common11

Which one should you actually buy?

Cooper Discoverer STT PRO

Dunlop Grandtrek AT20

Winner: Cooper Discoverer STT PRO — better wet, dry and handling. Pick the Dunlop Grandtrek AT20 if noise matters most to you.

Pick tire A Your priority is wet-weather safety

Cooper Discoverer STT PRO scores 68 vs 42 on wet.

Pick tire A You want the most grip on dry roads

Cooper Discoverer STT PRO scores 65 vs 41 on dry.

Pick tire A You enjoy sharp, responsive handling

Cooper Discoverer STT PRO scores 52 vs 33 on handling.

Pick tire A You drive through snowy winters

Cooper Discoverer STT PRO scores 67 vs 49 on snow.

Tire A · Cooper Discoverer STT PRO
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Tire B · Dunlop Grandtrek AT20
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Discoverer STT PRO or Grandtrek AT20?

Which is better in the wet, Discoverer STT PRO or Grandtrek AT20?

Cooper Discoverer STT PRO, 68 vs 42 on our wet score.

Which grips better on dry roads, Discoverer STT PRO or Grandtrek AT20?

Cooper Discoverer STT PRO, 65 vs 41 on our dry score.

Which is better in snow, Discoverer STT PRO or Grandtrek AT20?

Cooper Discoverer STT PRO, 67 vs 49 on our snow score.

Which is quieter, Discoverer STT PRO or Grandtrek AT20?

Dunlop Grandtrek AT20, 56 vs 53 on our noise score.

Which is more comfortable, Discoverer STT PRO or Grandtrek AT20?

Cooper Discoverer STT PRO, 55 vs 43 on our comfort score.

Which lasts longer, Discoverer STT PRO or Grandtrek AT20?

Cooper Discoverer STT PRO, 62 vs 51 on our treadwear score.

How do we compare tires?

Every category score blends two independent signals. 60% comes from professional tire tests (braking distances, lap times, noise measurements), each result compared with every other tire in the same test and newer tests counting more. 40% comes from owner reviews found online, adjusted for how generously each site rates. Both use one scale: the average tested tire gets 70, the best 100. When a tire has only one of the two, the missing half is estimated from the other and the score stays closer to average; with no road test and fewer than five owner reviews it gets no score yet.

Handling is the exception: road tests measure it inside the dry and wet scores, so its own row comes from owner ratings only and starts as less important.

Community buzz from Reddit and forums is shown for context only — it never changes the score. Full methodology