Cooper Discoverer A/T3 Review

 In 5th Gen Mods, Off-Road, Reviews

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.

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Showing 26 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.

  • Dianna Sharps

    Bob is quite right about the rocks here in AZ. Some are as sharp as glass. I tore up one of my street tires on a gravel road out here. Some very nasty stuff. I’m looking into a 4Runner myself and this is a great site for a newbie like myself. Don’t care for the stock tires they come with but I’ll use them up first. Going with theses tires have you noticed have you noticed any impact on your MPG? Great article but my first thing to spend money on is a good set of rock sliders and a front mounted winch. Thanks for the great information. Looks like you found a set of winners!

    • Clint Taylor

      The stock tires aren’t anything special; however, they do work surprisingly well. There is a slight loss of MPG from going to Cooper Discoverer A/T3 in 275/70R17. As I mentioned in the article, they have a slightly larger diameter and are a little over 10 lbs. heavier per a tire. This will cut down your MPG, but not significantly. From the numbers I’ve been calculating, you can expect a little under 0.5 MPG loss.

  • Kevin Lamb

    Hello, I’m new to the group. I was looking for your thoughts on the toyo open country at2s at a 275/70r17 vs the BFG KO2 and the Coopers?

    • Brenan - Trail4R

      Kevin, I currently drive two 4Runners, one with Toyo AT 2s and the other with the KO2s, and previously a set on Nitto TGs. Both are good tires, both have a similar tread depth and weight. The KO2 does weigh a little more and the Toyos have a deeper tread depth at 16.3/32″ vs the KO2 at 15/32″. I just checked and did not see a 275/70R17 on so I compared the 285/70R17 which is a little more common. Both are going to be really good tires, and it is hard to compare them in a head to head battle, it really depends on how you intend on using the tire. There are many factors that go into buying a tire right? Not too bad on MPG, not terribly loud, good tread depth, good sidewall, good life expectancy (tread wear), handle well in every season and terrain, etc. The question is very relative to me, and is an interesting one to answer as there is no true end-goal on how you ended on using the tire. I would start there, read a shit-ton of reviews on how people use the tire, how you intend on using the tire and then go from there. I wanted a tall, light, aggressive, long life expectancy, incredibly agile off and on-road tire, which is why I bought the Toyos. My girl bought the KO2 because someone at a tire shop recommended them and didn’t know any better. KO2s are a safe bet, but it really depends on how you intended on using the tire. No experience with the Coopers. Nitto TGs did wear out pretty quick in my opinion. Lincolns’ head was clearly showing at 40K miles.

    • Clint Taylor


      From an overall perspective I think either of the three tires would be great. As Brenan mentioned, I do not think there are Toyo Open Country in 275/70R17, so you’d have to go to 285’s and this would require a lift. The KO2’s are somewhat the default for all-terrain tires, and they are no doubt good and probably the most off-road worthy of the three tires. However, I will argue they might be the least on-road worthy of the three tires. I have had a little experience with all three of the tires you are interested in (mainly the KO2 and A/T3), and I will say I have been most impressed with my Cooper Discoverer A/T3 in 275/70R17, of which I have several thousand miles on now. This said, I prefer a tire that seems like you are on a highway tire when on-road, but can really grab when you are off-road. There are several articles online that review the A/T3 and nearly every single one has the same conclusion…the A/T3 has one of the best on-road traction of any all-terrain tire and can really handle itself off-road, a true all-terrain tire. I have come to the same conclusion after a few thousand miles on my A/T3. Since I really only have experience with the KO2 and A/T3 (and these are the only tires discussed that are in 275/70R17), I would recommend the A/T3 for better on-road handling and the KO2 for better off-road handling.

  • Mark

    The Cooper A/T3 P285/70R17 is only 44lbs but its rating is less than C. I have read in some places that a P rated and C rated are both 2 ply and pretty equivalent. Is this true? Is the 7lb savings compared to the 275 worth the less rating?

    • Clint Taylor

      Mark, I am sorry but I do not have any experience with P rated tires, only C and E. I would recommend purchasing the tire size you want though – 285’s or 275’s. They both have their advantages so I would make that your determining factor versus the weight.

  • Dee

    Did you use the stock 17 inch rims that came with the stock 265 tires, for your new 275 tires?

    • Clint Taylor


      Yes, I used the stock 17″ wheels that come with the TRD Off-Road 4Runner.

  • Dee

    The (3) new 2018 AT3’s are up for sale now.
    The only 275/70R17 they offer now is in the LT series with an E load rating.
    I’m concerned about the heavier E tire (52 lbs) and stiffer thick sidewalls that will effect gas mileage and highway ride comfort.
    I really like the looks of your 275’s in your photos, especially since they appaerntly will fit stock rims and a stock un modified Gen 5 (2016 Trail Premium) 4Runner? I hate to have to go with 265’s again, although many seem to be getting the 265 tire in the AT3 4s model, which are all in the STD load ratings (43 lbs).
    My other option may be to locate some of the older 275’s which were available in the C load rating I believe, and have them installed. The older 275/70R17, C load rating is showing 51 lbs??
    What are your thoughts on all this?
    Thanks for all your time spent.

    • Clint Taylor

      Dee, the 275’s are really a great upgrade over the 265’s. However, if you are not a hard core off roader, the load E tires will give you a harsher ride quality and not as good on road traction. I would not recommend the load E tires unless you were looking for a really durable tire and willing to sacrifice ride quality and on road traction. The older 275/70R17 in a C load rating is 51 pounds per tire. I was concerned with this before purchasing them, as it is about 10 pounds heavier per a tire in comparison to the stock tires. However, after 2,000 miles with them on I haven’t noticed any loss in power and only about 0.3 – 0.4 MPG loss. I will say the 275/70R17 in a C load rating have great on road off road traction. Very good wet weather traction as well. I would try to look into some older 275/70R17 in a load C rating. This gives you a bigger tire and can fit on a stock 4Runner without any modifications at all. In summary, I would just be cautious of getting load E tires. Try looking into some load C AT/3 if you can find them in 275/70R17.

    • Kevin

      I’m looking at the AT3 4S. They come in 255 75 r17 which is very close to the 275 70 r17. Basically only .7 inches thinner and the tire only weighs 39 lbs too. Just noting that it might be an option for you.

  • Dee

    I’m going to install a set of the older AT3 tires (LT275/70R17) Load Range C on my 2016 4Runner.
    I’m seriously dissapointed that Cooper Tires has discontinued this size tire with a Load Range C, in their new line.

    Looks like lots of 4Runner people are getting the new AT3 4S in the stock 265 size and Load Range STD for their 4Runners (not available in a 275), and seem to be happy. More time will tell. The 4S is not offered in the 275/70R17 (more dissapointment).

    The Load Range STD still sounds a little light for my 4Runner highway and mild-medium off road use. Load Range E sounds too heavy unless you really pound it off road and carry a lot of weight on the highway. The Load Range C sounds about perfect for average 4Runner or Tacoma useage.

    For comparison purposes- The current-new line of AT3 tires have the 265/70R17 available in both the 4S (STD Load) and the LT (C Load). See Below…

    Specs on the 4S (STD Load) show: 14 (1/32nd’s) Tread Depth, 8.27 Tread Width, 31.42 Tire Diameter, 43 lbs.
    Specs on the LT (C Load) show: 16.5 (1/32nd’s) Tread Depth, 8.62 Tred Width, 31.57 Tire Diameter, 47 lbs.

    So, there are some differences. The 4 extra lbs may be a stronger tire construction, which could turn out to be important. Plus the tread depth difference. I think Cooper Tires has made a mistake by reducing their number of C Load Range tire models (which seem to be near perfect for 4Runners and Tacomas), and also reducing what I see as a popular upgrade size of 275 which requires no modifications and fits stock rims (4Runner).

    Bottom line: Do some research into the 4S in STD load vs a C or E load range to be sure you are getting what you need.

  • Kevin

    I should be fine with STD load tires as that’s what the stock ones are and I haven’t had any problems. I sold my boat and am not an “off roader.” I just hunt throughout the year and get off the beaten path. I’m in Texas, so I don’t really have any problems with rocks tearing up my sidewalls. I also drive 50 miles to work and back and deal with a lot of rain down on the gulf coast and some freezing temps in the winter. I’m just saying this so you can see wheee I’m coming from when I lean towards the at3 4s. My concern with sizing is basically the width of the 255 75 17. I haven’t seen enough of them “in the wild” to know if they look goofy. This would be my first “skinnier” tire as my jeeps and broncos in the past have always had wide tires. I like your idea of going back to the older AT3 but I can’t get over the look of the sidewall, I just am not a fan. Just me being vain I guess.

  • Dee

    I located the older AT3’s at Tire Rack for $162 each. May have gone to $172 now.
    As Clint said, the 275/70R17 (C load) fits nice, but with only about 0.5 inch clearance at full turn for me. The tread look is considerably more aggressive than the old Bridgestones, and as Clint said, I can’t detect any louder road noise either. Haven’t had it off road, but drives smooth so far. I’m pretty happy. The side walls look just like the ones in Clint’s photos.

    I read somewhere in a Range Rover Test article that they used tall but thinner tires, and the author liked them for what he called exploring type vehicles. There must be worthwhile advantages to a thinner tire in certain conditions. Not to mention weight and gas mileage. Lots of people have gotten the STD load and seem to be happy. By the next time I need tires, the C load may not be available, and I’m not gonna go E load, so I’d probably do the STD load too.
    But for now I’m very happy with the AT3 C load. Tire Rack may have selections of the older AT3’s in sizes (thinner) and loads you want. But then there is your issue with the side walls….. lol.
    Good Luck.

    • Clint Taylor

      Dee and Kevin,

      I am glad to hear the 275/70R17 are treating you well and you like them. In regard to the comment of a taller and skinnier tire, such as 255/75R17. The reason for a tire this size is because some people prefer a tire that sinks into mud and snow in order to get good contact with the solid ground below. Skinnier tires don’t have as much surface area as a wider tire so they will sink into the mud and snow so that you can potentially come in contact with hard ground. They also have a larger diameter, therefor lifting your vehicle slightly. Although all this is something to consider with skinnier and taller tires…it is not very feasible in my opinion to get skinnier and taller tires for this reason alone. Skinnier and taller tires will give you much more flexion in the tire due to a taller sidewall, and therefor decreasing your handling capabilities and increasing body roll. Skinnier tires also do not give you great traction for any situation outside of deep mud and snow…which most people are not in deep mud and snow a lot, if at all. In consideration of this, a wider tire, such as the 275/70R17, gives good on road and off road traction. The amount of traction I gained from going to the wider tire (as well as the A/T3 tread pattern and compound) is significant and I wouldn’t prefer to go to a skinnier and taller tire which would result in less traction. All this said, if you prefer the look of a taller and skinnier tire then that is a justifiable reason to potentially purchase that tire type.

  • Liam

    Will a 275 fit gen5 SR5 model without rubbing?

    • Clint Taylor

      Liam, if you are running the stock wheels and stock suspension these tires will fit.

  • Alvin

    We have a 2018 TRD pro. I’m still undecided on putting 285/70/17 + toytec 2″ lift kit KO2’s or just keep it stock and put 275/70/17 KO2’s. To be honest at the moment, I’m really after the aggressive look. Can anyone recommend a 275/70/17 tire brand that more or less look like you have a 285? Thanks I really enjoy reading from this site by the way.

    • Clint Taylor


      If you are wanting a more aggressive looking tire, I’d recommend the new Discoverer AT3 LT from Cooper Tires. They have a more aggressive sidewall. The BF Goodrich KO2’s would be an even better look for aggressiveness. With the suspension that you have on a TRD Pro I’d be slow to lift it. The TRD Pro’s come with a pretty solid suspension right from the factory. One thing to be aware of is that the TRD Pro’s come with a different offset wheel than the other 4Runner’s so you will most likely have to do some very minor fender trimming to fit 275’s.

      • Alvin

        Thanks Clint. Very informative. I did not know until now that 275 will not fit the trd pro without minor mods. I was informed by the dealership that i can fit 275 without problem. I want to avoid any trimming so would it be better to go for 255/75/ instead? And it’s cheaper i think. Thanks again.

        • Clint Taylor

          I have a 2017 TRD Off Road 4Runner with Bilstein 5160’s in the rear and Bilstein 6112’s in the front set to a 1.2-inch lift. I also have the TRD Sema wheels (which push your tires out .45-inch on each side do to the +1 offset). This is a near identical setup to what you have on your TRD Pro 4Runner. In consideration of this, the Cooper Discoverer AT3 in 275/70R17 that I installed had slight rubbing in full crank when driving in reverse. I would suspect you will have the same issue.

          I was just like you, I didn’t want to do any trimming at all. It is extremely minor trimming though and I was able to fix it quite easily. If you want more information on this, just send me an email by clicking the “letter” next to my short biography.

          I like a wider tire as it gives more pros than cons in comparison to a 255/75 sized tire for example. It ultimately comes down to what you want though. You definitely have two solid choices for 275/70R17 between Cooper Tire and BF Goodrich.

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