Looking for advice after multiple flats on Cooper AT3's with Discovery 4

#1
Hello everyone. I was hoping you could give some suggestions. I live in Reykjavik and I have had my Discovery 4 just over a year. I bought Cooper Discoverer AT3's last May, used them for the summer, and then switched them out for Nokian R2's for the winter. I have them in 265/65R18 on Compomotives. I just switched back to the summer tires in the beginning of June (I was gone for May, and we get snow and ice into May here). I have had really bad luck with the Coopers. My total mileage on the car is 26000km, and the Coopers have been on for only about 12,000 of that. In that time I have had at least four flat tires requiring patching or replacement. I bought one new tire (so I have bought six so far). Just yesterday, I had two separate flat tires. One occurred on a mountain road. I had lowered the pressure to around 27 or 28 psi. It was a front tire, and it was in the center of the tread. The leak was fast, but not catastrophic. I did not notice when it happened, as I had deflated all my tires so the TPMS lights were already on. I noticed when I got into town and needed to air up. (it was only 1 or 2km from the trail head, so I was not driving long or fast on the flat). The next flat was the rear tire on the other side. It was fine when I aired up in town, and I put 34 psi on the tire in town. I drove about an hour and arrived in another town, and noticed that it was also hissing. Sure enough, it had also lost pressure and was spraying air out a hole in the tread (not the sidewall etc). It was not the spare tire, but one of the other ones that had been on the car when I was driving before. It was near midnight on our independence day, so no luck in getting anyone to help...I was still an hour away over a mountain road to the place I was staying. I bought some tire fixing foam spray at the gas station before it closed and followed the instructions, and it seemed to work for a little bit, but it seemed to lose pressure gradually. When I drove the requisite ten kilometers, I stopped to check, it was still spraying out air and foam all over my wheel well. I had a call and get a friend to pick me up and drive me out...a two hour round trip for them at midnight. They were very kind about it, but I was mortified.


In the other occasions, I had one flat in the highlands from having too much pressure on gravel roads. I was using the standard factory pressure on a gravel road, and the tire hit a rock and it tore up the tire. I cannot remember the specifics of the other one or two, but I am pretty sure it was either a piece of metal, or just the bad highland roads here. I have had zero problems with the Nokians, but I am not running these on as many trails or highland roads, as they are all closed in the winter.

I have lost my confidence in these tires completely, and I am wondering what is the issue. Should I switch to another tire like the KO2? Are my pressures too high or two low? I generally follow the factory pressures for road use, and air down to around 28 or 30 for trails. I would like to think that I am not driving like an idiot, but of course that is possible. I drive fast over gravel at times, but in general I am a careful driver. On these mountain trails I was rarely going over 20 or 30 km/h, and most 10 or so. Primarily in low range for the passes and so on. The tires seem to work very well when they are not exploding. Tires are exceptionally expensive here, I think the Coopers were around 400 dollars each, but Costco just opened here and is crushing our local monopolies, so all of a sudden they are 30-50% cheaper. That's good news at least. I am not sure what brands they offer other than Michelin though.

On the plus side, the trail and view was amazing!
 
#2
Which load rating are you running? Cooper makes that model and size in both LT and E rated tires--you should be running E.
 
#3
They say 114 T, standard load. There is an E on the tire, (actually an E with a lower case n next to it). I believe this is all the importer had here...it is was they recommended.
 
#5
First issue is the tire pressure, airing down with small sidewall and a 7000+ lb vehicle will pinch any tire on rim, regardless of brand or load rating. Lots of info online and Facebook for similar issues, I've shared my learnings with 12 years of owning both LR3 and LR4 as well as all tire brands. I've never had issues running at 45-50 psi, any lower is for sand only. My GY MTR's with Kevlar 1 day old pinched on a flat road, small rock at 30psi!

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#6
Thank you Bill. Is there a way to tell whether a flat is caused by pinching? The leaks were not at the edge of the rim, they were in the center of the wheel's tread., far from the sidewall...is it possible to pinch flat there as well? I would have thought it would only be caused at the edges where the rim has an edge.

Is this the general consensus with others? I find that off road the tires give a much better ride and grip at the lower PSI's. My factory recommendation is 34 and 37, but that is for the stock 255 55R19 tires that come with it. Generally I keep it at that for town and for light gravel roads, but for mountain tracks or long stretches over gravel, I lower it. My D4 has prospeed rock sliders, but is otherwise unmodified. I am usually on my own, and my gear load is not that bad, maybe about 50kg of various camera gear and other junk.
 
#7
Yes i suspect a rock puncture or pinch can be related to tire pressure being low and compressing to rim. Next time your out place a gopro near your tire, deflate to your typical psi and watch how the vehicle weight compresses that tire when rolling over a rock. I promise you will be amazed and wonder why you ever deflated in the first place!

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#8
I can't see the entire rating on the tire from the picture but my research on Cooper says that tire is not rated for the weight of a Disco 3/4. I think that tire is about 2600lbs at operating PSI. Airing down significantly changes the load capacity and function of a tire and I think that is your issue as billj214 said.

I'm no tire expert, but the 114T speed rating is usually a lower gross weight tire as well in relation to truck/suv tires. I also was not able to find anything on Cooper or associated distributors that recommend that tire for a Disco 3/4 with 18" wheels. They do however recommend the same specs you are running for much lighter trucks, SUVs, and Crossovers. When you air down, you change all of those numbers associated with load, speed, sidewall, etc.

For example, the same BFG KO2 is recommended for your rig (LR3 18" wheel) is "E" rated, 122R speed rating, and 3300lbs with a MAX (not operation) 80psi. LR3/4 with factory size tire is somewhere around 33-42psi depending on what end of the rig you have it on. Airing down a few PSI on an "E" rated tire is much different than an under-rated tire on an overweight rig.

The best I can tell is that is that your tire is "C" rated, maybe "D" but doubtful (which would be LT) and around 2550lbs max load at operation PSI which is specific to the vehicle and tire combo. Keep in mind, depending on how your rig is loaded, PSI and airing down is different PSI from front to back. I would also checked for cracked wheels if your PSI was too low on a low pro tire, your wheels were probably taking a beating.

I hope I am wrong on all of this. I would call Cooper direct and ask them if the tire you have is recommended for your rig. Their STD and XL ratings are a bit different than most of us are used to.
 
#9
Their information says that it is a standard load with 2600 lbs rating. The tire was recommended by the Cooper importer here at the tire shop, and it was also highly recommended by Overland Journal...didn't they use it on LR4's as well? I could have confused the two things. In any case, I specifically asked the shop about the load rating when I bought them, and the guy said it would be fine, as it was the same or higher than the stock tires. Perhaps he was selling me a load of B.S. (would not surprise me anyway). That said, 2600 pounds per tire and a 7100 lb vehicle would mean that even with three tires, the load per tire is 300lbs lighter than the load rating. Does anyone know how much they lose upon airing down? I am not trying to avoid the inevitable if they are not strong enough, just trying to figure out what would constitute strong enough...is it enough just to increase the pressure, or do I need to buy five new tires for what will likely be 2000+ dollars in this country...

P.S. I will definitely have them check for cracked wheels. That said, the PSI was never below 27 psi on the front for any amount of speed...stock said 34. I lowered them down to 27 for a mountain road where I was going slowly. I am staying an hour journey along a mountain road and for this trip, I have put the pressure at around 30-31 front (again, from 34) and 33-34 back from 37. I did not think these were super low, especially since the tire has quite a bit more sidewall height than the factory (the factory ratings are for 255/55R19, and mine are 265/65R18).
 
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#10
Regardless of the brand you choose I would highly recommend making sure you are running an E rated or tire with a much higher load rating (such as these in a 122) as others here have stated. LR's are heavy. The tire might have been recommended by Overland Journal and your tire shop but on the wrong load rating that means little.
 
#11
Their information says that it is a standard load with 2600 lbs rating. The tire was recommended by the Cooper importer here at the tire shop, and it was also highly recommended by Overland Journal...didn't they use it on LR4's as well? I could have confused the two things. In any case, I specifically asked the shop about the load rating when I bought them, and the guy said it would be fine, as it was the same or higher than the stock tires. Perhaps he was selling me a load of B.S. (would not surprise me anyway). That said, 2600 pounds per tire and a 7100 lb vehicle would mean that even with three tires, the load per tire is 300lbs lighter than the load rating. Does anyone know how much they lose upon airing down? I am not trying to avoid the inevitable if they are not strong enough, just trying to figure out what would constitute strong enough...is it enough just to increase the pressure, or do I need to buy five new tires for what will likely be 2000+ dollars in this country...

P.S. I will definitely have them check for cracked wheels. That said, the PSI was never below 27 psi on the front for any amount of speed...stock said 34. I lowered them down to 27 for a mountain road where I was going slowly. I am staying an hour journey along a mountain road and for this trip, I have put the pressure at around 30-31 front (again, from 34) and 33-34 back from 37. I did not think these were super low, especially since the tire has quite a bit more sidewall height than the factory (the factory ratings are for 255/55R19, and mine are 265/65R18).
Regarding the above in bold, having a 300 pound margin for any one tire isn't very much. For example, if you are on a trail with rocks or ruts and your right front wheel and left rear wheel are driving over a rock or high spot then they are carrying most of the vehicle weight, effectively almost doubling their normal load and far exceeding the 300 pound margin mentioned above. You may want to consider Cooper St Maxx, BF Goodrich KO2 or any other 3 ply sidewall tire in Load Range E as well as replacing those 18" wheels with a 16" so you have a larger, more forgiving sidewall that is less likely to get pinched as already discussed. The new Yokohama Geolandar G003 M/T has 3 plys as well (Available July 1 in the USA)
 
#12
In my experience with the Discovery 3,4 you can't even air down that much on a non E rated tire before it gets seriously bulged out. It used to be a rule of thumb that the dealer specced tires for the cars only if they were rated to take the weight of each axle on on tire, IE two tires touching the ground instead of four.
 
#13
Ok, thank you all. I talked to another tire shop today (in another part of the country, where I currently am), and they said that the tires I have were among the best available in my size for the Discovery. They do not sell Cooper, so they had nothing to gain from telling me this. They only had Yokohama Geolandar ATS tires available in something similar. In any case, I had them just fix them up. I will look into the BFG's, but I think that no one here really has the correct tires available, nor do they seem to know much about the Discovery and what it needs. This is odd, as it is a very common car here.

Offroadmuch -- I would love to get 16 or 17" wheels, but the very smallest possible on the D4 is 18", and only then with Compomotives. I am using the largest tires possible without lifting the car or modifying the wheel wells.
 
#15
Correct!

From what I can see, Cooper Discoverer AT/3 comes in a 265/65R18 in two different ratings; they come in a P265/65R18 114T (C Rated) advertised for use on SUV page and LT265/65R18 122R (E Rated) advertised on the Light Truck page.

1) P265 with speed Rating T with Load Index 114 is for 2601lbs which by my research would be a "C" rated tire and not suitable for offroading air downed Disco 3/4 weight vehicles.
2) LT265 with speed Rating R with Load Index 122 is for 3307lbs which by my research would be an "E" rated tire and I think the one rjl found as well. Much more suitable for the weight of the vehicle.

The picture of your wheel clearly shows a 114T Load Index/Speed which signifies its most likely the P265/65R18 114T (C Rated). Although the C rated could meet the minimum spec of the vehicle, I do not believe it is the right tire for the conditions your vehicle is being operated and I am sure that is exactly what the saleman/warranty guy will tell you.

Hope this helps out....I can post links if you want. Can you post a pick of the entire tire from the peripheral so we can zoom in on all the markings?

Honestly I believe its the tire spec that is the problem here.
 
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