So, I recently purchased the KO2's in the 275/70r17 size for my stock 2014 Trail, and decided to follow the advice on this thread to get me started. Over the last few weeks, I've learned a little more, and thought I'd share for anyone else looking at them for their ride.
1. LT275/70r17, E load tires at 45 psi are a hell of a lot stiffer than stock tires. I read this before buying them, and knew it to be the case, but didn't really KNOW it until I drove it. The problem for me wasn't the "comfort" aspect, as much as the combination of the higher spring rate of the tire itself and its added mass. The result was that sharp bumps like potholes or abrupt changes in pavement caused the wheels to loose contact with the road momentarily, since my stock suspension isn't exactly setup for that much stiffness and weight on the end that touches the ground. I was like: :lookout:
2. After lowering my pressure down to 42 psi for the safety aspect, I definitely felt the tires become a little more compliant with the staccato road features, and I was generally satisfied with them, but noticed a different issue. It happened to rain on my way to work one morning, and I pulled under the canopy of a gas station to fill up. When I did, I noticed that none of my tires were leaving wet tread marks on the dry concrete past about 1/4" out the outer lugs. Basically, I was only riding on the middle three lugs of the tires, and a very minimal amount beyond that (sorry, no pics). Surely this is not good for tread life or ultimate traction on pavement.
3. After #2, I broke out the big guns, and called my cousin; he's an engineer for Michelin (who makes BFG, for the uninitiated). I gave him the vehicle specs, and he said 45 was probably fine if I'm fully loaded, but recommended I try something like 35-38 when empty, to get a full contact patch. I went down to 38, and I have to agree. The ride is now [nearly] as comfortable as stock on the interstate (never had issues around town), and it seems to give a much better contact patch. No wet-to-dry footprints to see yet, but I can feel the weight of the steering changed a bit, and it gives me a lot more confidence at high speed.
Obviously, your mileage may vary :drum:
...but I'm happy at 38 psi for on-road use, and glad I got the 275's for that little bit of off-road advantage now that the pressure isn't causing them to jump around on the road. Hope it helps.
That's also a lot of tread contact area which increases rolling resistance a LOT. You can even hear the difference with the window rolled down when driving slowly (5-10 mph) on the road. Try 40 pounds if 45 is too much, it's a big difference in feel. I run 44 for mileage, 30 for desert offroad, 24 for rock climbing and 20 for sand dunes.
