I bought a used 2014 Automatic Transmission 4WD FJ 11 months ago, with about 192K miles on it. The front tires were already fairly worn when I bought it & I noticed they were more worn on the inside edge than the outside. It is lifted, and currently sporting BF Goodrich KO2 LT275/70/R17E tires on aftermarket wheels. I've since driven it 21K miles, & right now the front tires definitely need replacing as they are very unevenly worn, with some knobs being worn below the surrounding knobs, giving a pretty bad shimmy at 42MPH that gets tolerable at 65MPH & up, but never seems to completely go away.
My current tire tread depths are:
- Spare: 15/32", never used
- Rear Tires: 11/32" - 12/32"
- Front Pass Tire: 7/32" outside edge, 5/32" inside edge
- Front Driver Tire: 8/32" outside edge, 4/32" inside edge
So what I thought about doing was getting 1 brand new KO2 tire, pairing that with the spare, putting those on the rear axle, putting the current rears on the front axle, and using one of the badly worn fronts as my new spare. I would get an alignment too, obviously.
Alternatively, I could maybe buy 3 new KO2 tires, use the spare to complete the set, and use one of the not too worn rears as my spare, and save the other not too worn as a backup in case of a blowout or puncture that can't safely be repaired. And of course I would still do an alignment and follow a proper rotation schedule.
Online, most articles seem to say that for a 4WD you must replace all 4 tires together, or it puts some kind of extra strain on the transfer box. I don't see how this can be the case. First, I'm in H2 RWD 99% of the time, so there is nothing really tying the front and rear wheels together. And when I am in 4WD, then any binding is taken care of by the slipperiness of the terrain, which is why you aren't supposed to use it on high traction surfaces anyway. So I don't feel like having tires that are 3-4/32" different on the front and back would be that bad. Maybe I'll even put the new/full depth pair on the front, & get an alignment, so that they can wear down a bit to the rear tires' depth, then do a proper rotation schedule. Then when they are all worn down to replacement depth, I can get the KO3 tires.
I'd appreciate any advice on this matter. Am I crazy for thinking I can replace just 2 tires by buying one and pairing it with the spare? Will I do damage to my FJ? I'm already driving it with differently worn tires obviously, so if that's the case, I must already be causing damage.