Cooper Discoverer A/T3 Review

 In 5th Gen Mods, Off-Road, Review

Cooper Discoverer A/T3 Tires on 5th Gen Toyota 4Runner

Cooper Discoverer A/T3 Tires on 5th Gen Toyota 4Runner

Cooper Discoverer All Terrain 3 Tires – Complete Overview and Review

For those of you who are wanting to upgrade your 5th Gen 4Runner in both looks and off-road performance, but still maintain good on-road performance, you might want to take a look at the Cooper Discoverer A/T3… in 275/70R17.

Although the stock 5th Gen 4Runner is an amazingly capable vehicle right from the factory, there are always upgrades you can do. I have always been hesitant to do upgrades which compromise the vehicles on-road performance. Such things I am referring to are braking distance, handling, gas mileage, road noise, and ride quality.

There is a reason luxury cars do not have mud terrain tires with 6-inch lifts. This makes for a terrible ride quality but is necessary if you are going hardcore off-road (or if you just want the look of such a setup). The more you start to lift your vehicle and put on larger tires, the more likely it is to have decrease in gas mileage, decrease in handling, decrease in ride quality, and pretty much a decrease everywhere except for off-road performance and visual aesthetics.

There has to be a middle ground of increasing your off-road capability and all-terrain visual appeal while still maintaining a safe and comfortable on-road SUV. In my opinion, there definitely is.

I have been researching upgrading my tires for several months now. When I say research, I really mean research. I am an engineer, so I have looked at many different aspects and considered many different options.


I have always thought 285’s on a 4Runner look awesome. You are getting a lot of off-road benefit from the larger tire and you are definitely increasing the visual appeal of a 4Runner by doing this. However, there are a lot of drawbacks:

  • Decrease in gas mileage
  • Increased road noise
  • Spare tire might not fit in factory location and departure angles might be decreased
  • Decreased acceleration, braking, and handling
  • Significant lift required.
  • May need new wheels and or spacers

Although 285’s (or 33”) tires add a lot of off-road prowess, you have to spend a substantial amount of money to do so, and your on-road performance will suffer. I do believe 285’s are a great choice if you find yourself off-roading in your 4Runner frequently. However, you will take a significant loss in on-road performance when going to 285’s and will also have to spend a substantial amount of time, money, and work to get the right setup.


The stock tires on all 5th Gen 4Runner excluding the Limited is 265/70R17 (which correlates to a 31.7” tall tire). These are great and give you enough off-road capability while still giving you good on-road performance.

You really can’t go wrong with this tire size, as this is the tire size Toyota designed the 4Runner to come with from the factory. There are a lot of different all-terrain tire options that are in the factory 265/70R17 size.

You can have some differences in gas mileage and handling depending on the tire you get, but for the most part you will have very similar handling to a stock 4Runner. For a conservative approach, I’d recommend going with an all-terrain tire in a 265/70R17 size.

275’s – The Size I Chose

Cooper Discoverer A/T3 Tires - Size Options

When I was selecting what tire size I wanted, there were a few things I wanted to make sure I had:

  • Not a significant loss in MPG (less than 0.5)
  • Very little to no increase in road noise
  • Good wet traction capability
  • Good ride quality
  • Spare tire can fit in factory location
  • Good overall visual appeal (not to important but I did consider it)
  • An overall good all-terrain tire (good on the highway and on the trails)
  • No lift required

So what tire size did I chose? I chose 275/70R17. I will say that after lots of research I think this is an excellent option for anyone wanting to upgrade their 4Runner and is the middle ground between 265’s and 285’s.

Let’s take a further look at each aspect I considered in comparing the Cooper Discoverer A/T3 in 275/70R17 to the factory Dunlop AT20 tires in 265/70R17.

Ride Height

Cooper Discoverer A/T3 Tires - Ride Height

The stock Dunlop AT20 tires on a 4Runner are 31.7 inches as previously mentioned. By going to the Cooper Discoverer A/T3 in 275/70R17, you are going to a 32.2-inch tall tire. This is an increase of 0.5 inches.

What this does is not only give you a larger tire (which looks better in my opinion), but it will also lift your entire 4Runner 0.25 inches. I know this might not sound like much, but there is a subtle difference and a definite increase in ride height…just 0.25 inches. This small increase in ride height is a small increase in off-road performance.

This additional sidewall height also allows you to air down your tires with a lower chance of scraping your wheels in hardcore off-road situations. This is probably not something significant to consider, but you do have more tire to work with.

Spare Tire

Cooper Discoverer A/T3 Tires - Spare Tire 4Runner

Due to the fact of going to a larger tire size, I also had to replace my spare. Something that is nice about a 275/70R17 tire is that you can fit this size in the factory spare tire location, just like a 265/70R17. Although there are some 285 sized tires that fit in the factory spare location, it can result in a decreased departure angle. Due to these reasons, many people will externally mount their spare 285 tire on their bumper or on the roof…which typically can require lots of additional costs and a decrease in the usability of either your roof rack or rear lift gate.


Cooper Discoverer A/T3 Tires - Rubbing

I personally did not want to lift my 4Runner much, if any, because I wanted to still have a good on-road vehicle. With the 275/70R17 tire size you do not need to lift your vehicle at all (of course you always can though). After driving on-road and off-road with the Discoverer A/T3 in 275/70R17, I have experienced no rubbing from this tire size. I have had at or near full articulation and have turned my wheels full crank in each direction without any conflict at all. This is a huge benefit for those of use who want to keep some on-road performance as lifting your 4Runner will decrease road performance. You also do not have to spend extra money on lifting your vehicle just to fit a larger tire as you would with a 285/70R17 tire size.

Road Noise

Cooper Discoverer A/T3 Tires - Road Noise

I wish I had conducted some sort of scientific road noise test like driving at 60 MPH with my stock tires and recording the dB level and then doing the same with my new Cooper Discoverer A/T3. However, I did not do this, so all I can give is a subjective opinion. I did not want much increase in road noise from going to a larger and more aggressive tire. Although I do not have any data to present, I can subjectively say I do not notice hardly any increase in road noise, and if there is, it is very minimal. I have been very pleased with the lack of road noise.


Sometimes more aggressive tires can decrease ride comfort by adding a little extra vibration. All-terrains typically don’t do this, but they can ever so slightly. I haven’t noticed a decrease in comfort with the Cooper Discoverer A/T3. Something that is important to mention is that I got the Discoverer A/T3 in a load C rating. This tire also comes in a 275/70R17 size with a load E rating. This difference in load rating will change ride quality. The load C will have the better ride quality, so if you decide to go with the more rugged load E tire, you might experience a loss in ride quality, but a more rugged tire.

Tread Width

Cooper Discoverer A/T3 Tires - Tread Width

By going from a 265 to a 275, you are gaining additional tire width. This not only improves the visual aesthetics of the 4Runner, but also gives your vehicle more surface area to gain traction from. The Cooper Discoverer A/T3 in 275/70R17 has a tread width of 8.86 inches.

Something I found interesting is that many other tire manufacturers do not list this value, so unfortunately, I cannot give too much of a quantitative comparison to the factory Dunlop AT20’s. However, I did try to measure the factory Dunlop AT20’s and it appears that my new A/T3’s are about an inch wider! This is a significant increase in width.

To me, this additional width was what I really wanted. It gives the 4Runner a much more planted look and there is no doubt that going to a wider tire will give you additional surface area, which in hand gives you more grip. I am very pleased with the additional width I received from going to the Cooper Discoverer A/T3 in 275/70R17… and all this without needing a lift.

Tread Depth

Stock 4Runner Tires - Tread depth

The tread depth of this tire is pretty deep, at 16.5/32 of an inch. The factory tires have a tread depth of 11/32 of an inch. This is a significant difference in tread depth.

Typically, this will contribute to more road noise. As I previously mentioned, there is very little added road noise, which is somewhat surprising when comparing the difference in tread depth as I thought there would be much more.

The additional tread depth is going to give your 4Runner much more bite in loose surfaces and benefit in any all-terrain driving you are doing.

You might experience a bit more ‘wondering’ on the road if this makes sense, because the extra tread depth allows your vehicle to wonder just ever so slightly more. This is very minimal and nearly negligible, so don’t make this a determining factor in getting this tire or not.

Tire Weight

Possibly one of the biggest concerns I had when going to the Cooper Discoverer A/T3 in 275/70R17 was the additional tire weight. The factory tires do not have a weight listed for them, but similar tires are around 40 pounds. The Discoverer A/T3 in 275/70R17 weighs 51 pounds…over 10 pounds more.

This is more than a 25% increase in tire weight. This increase in tire weight will decrease braking, acceleration, and gas mileage. However, after personally driving my 4Runner for a while now with the Discoverer A/T3 installed, I can say I do not notice much loss at all. I once again wish I could give differences in 60-0 braking times, 0-60 acceleration tests, and gas mileage tests.

However, I did not think I could do these tests with reasonable accuracy because the difference in results seem to be negligible. I will say that you will have to compromise weight when going to a larger tire, both in height and width. There just isn’t a way around that.

On-Road and Off-Road Performance

On-Road and Off-Road Performance

From my few hundred miles of testing the Cooper Discoverer A/T3 in 275/70R17, I can say I am very pleased with the balance of on-road and off-road performance. I honestly do not notice much, if any loss of on-road performance in comparison to the factory Dunlop AT20. The AT3’s have handled exceptionally well in daily driving, and once again, I do not really notice a difference in going from the factory 265/70/R17 size to my new 275/70R17 size, but I know they are benefitting me tremendously in all-terrain situations and in visual aesthetics.


Some concluding marks on the Cooper Discoverer A/T3 in 275/70R17 for my 5th gen 4Runner would be that I am very happy with the performance and value of the tires. They add to my 4Runner’s visual appeal and all-terrain performance without compromising on-road handling.

If you are wanting to go to a bigger tire without the downsides of going to a 285 size tire, I’d recommend taking a look at the Cooper Discoverer A/T3 in 275/70R17. It is a great fit for the 5th Gen 4Runner and makes it even more of an all-terrain vehicle. I’ll even go so far as to say I believe Toyota made a mistake in not making these tires the factory tires on the 5th Gen 4Runner – I really like them.

Love the 4Runner Lifestyle?


Join the 5th Gen 4Runner community and get access to new gear, specials, free stickers, free decals, step by step installs and much more. Get access to manufacturer discounts, sales, coupon codes and so much more.



Recent Posts
Showing 4 comments
  • John - TRD Off-Road

    Thanks for the great article. I have been debating between the C load rating 265 BFGoodrich KO2s and the E load rating 275 BFGoodrich KO2 tires to replace my factory Dunlops. I don’t plan on adding any more lift then the one inch I got on the front from adding the Bilstein TRD Pro suspension, so these two sizes are my only choices without trimming. I had two E load rating KO2s stop balancing on my Xterra a few years in, but Discount Tire replaced them for free. They said part of the problem is the Xterra is a pretty light vehicle for an E load rating tires, so that makes sense. The 4Runner is a little heavier, and they said I would likely not have trouble. I found it interesting that the Cooper tires are a full one inch wider at the tread, when the side walls are only one centimeter wider, but your great picture shows the Dunlops tapering in before it gets to the tread that actually makes contact with the pavement, so that totally makes sense. Again great article, gives me more to think about, leaning towards the 275s I think…

  • Clint Taylor

    John, I am glad you liked the article. 275’s are a great choice, especially with the 1-inch lift you have in the front. I will say load E tires are great, rugged, and an awesome thing to have if you want the most durable tire you can get. However, they can have balancing issues on occasion and will give a harsher ride quality in comparison to a load C. Whichever you go with I think you will be happy. I think the 275 is definitely worth the extra width.

  • Bob D

    Great article. One of my main concerns was airing my factory Dunlops down and not puncturing my sidewall in the harsh rocky terrain of offroad Arizona. I also don’t want to lift so it looks like the A/T3 275/70R17 is the tire for me. Thanks

    • Clint Taylor


      Glad this article could help you out. The A/T3 in 275/70R17 would be a great choice for what you are describing. You might want to consider the load E tires if you are worried about punctures.

Leave a Comment

Start typing and press Enter to search

Bilstein 6112 & 5100 Install - 5th Gen 4RunnerEastwood Rubberized Rust Encapsulator