Hi all. Decided to post this here even though the subject is not GFC related, exactly.
Who has dealt with offroad tire cupping? I’m looking for general info and maybe corrected expectations…
I have a 2019 tacoma. GFC build 706 V1. I have about 30K miles on Cooper Discoverer ST MAXX 10 ply tires. They are cupping and really noisy. I can deal with the noise and cupping, I suppose, but want to learn how to try to avoid this with future tires, if possible. I believe that my suspension is in good shape as the truck rides very well. I have bilstein 5100 on notch 4 up front, dakar medium leafs with ome rear shocks. I plan to do an alignment and have my suspension inspected by a trusted shop. I understand that my current tires cannot be corrected. I feel like 30K miles is a little bit soon to be having problems.
Is 30K par for these offroad beasts? Should I adjust my expectations?
I’d say see what the alignment says first. If it’s been out of spec that’s your biggest reason.
I have some cupping on my K02’s that I think is a result of the alignment changing just enough over time, longer than optimal time between rotations sometimes, and worn suspension (new suspension just arrived and going on soon).
On a serious note, mine are usually around 33-35 on the highway after warming up. This morning, some were around 28-30 due to the chilly 37º F morning in Montana.
It seems counterintuitive, but I remember going down the rabbit hole researching one time about E load tires requiring more air pressure than C load. Because common sense would tell you to run lower pressure, but according to everything, I read, that isn’t the case. They required higher pressures.
This is in no way based on personal experience, I have C load on my Tacoma.
Yes, but 10 ply = E Rated. So while they can handle low pressure off road they actually require more pressure than a C Rated on road because they were designed around those higher pressures.
I think that 36-38 was the recommended consensus for a Tacoma.
So I’ve been doing a shallow rabbit hole dive. Some of what I’ve seen so far is in line with what @cmc is saying. I found this from one source, but others have echoed something similar.
This was quoted from one internet source, so take that for what its worth…
“Below about 45 psi the LT-Metric LRE tire actually has a lower load capacity than the P-Metric tire. The reason for this is a bit technical but boils down to the tire’s ability to shed heat. An underinflated tire commits suicide by overheating and because the LT-Metric LRE tire has a heavier and thicker construction, it generates more heat through internal friction (for the engineers, greater hysteresis) than the P-Metric tire if it’s underinflated.”
Maybe I’ve been slowly wearing my tires prematurely due to lower psi and excess heat on-road. I certainly do air down for off-road situations when needed.
So many things can lead to cupping but I’ve seen lots of feedback about the coopers cupping.
Hard to say if you’re running to much pressure. I run 35psi on my Duratracs (285/75/16 with an E rating) but I also have a lot of added weight with 2 spares, skid trilogy, front bumper with a winch, rear HC bumper with a swingout, a supercharger, and the GFC.
Best way to confirm proper tire pressure is a chalk test and it’ll work alright on cupped tires but you should do this on a new set ideally when the tread is an even depth in the center and on the sides of the tread pattern.
Changed all tires to 44 psi cold. Cupping sounds are less, I think. Rained last night and looks like rain over next few days, so I’ll do my chalk test when its drier. I’m interested to see how that comes out.
Anyway, I’ll report back…
I’d be curious what the chalk test shows at 44 psi. I would imagine you don’t get anywhere near the entire tread width. Of course the road noise is down because you’ve narrowed the tread contact to the road at that psi.
I run Cooper AT3 XLT in load range F. They’re stiff but when I did the chalk test, I came to the conclusion that 32 psi cold was the correct pressure.
That chart is referring to SINGLE tire load capacity. Tacomas and Gladiators with a GFC loaded down probably have a single tire load around 1600. The overheating issue is referring to an under inflated tire that is over loaded.
The most probable reason behind your tire cupping issue is over inflation or poor rotation intervals.
How often do you rotate? Mud tires in my opinion shouldn’t go over 3000 miles between rotations.
so, 33psi would be correct assuming you and everything in the truck weighs 6,000lbs. 3,000lbs per axle, 1500lbs per tire.
I’d go weigh your truck after loading up for camping and recheck the math. My truck’s front axle is 3,000lbs and 3500lbs on the rear when I’ve loaded up. Chalk test is good too, but I’d go weigh your truck loaded up. E series tires are gonna ride hard, heavy too. But if you’re doing Rubicon trail stuff, makes sense to have them. Forest roads? way overkill.
