Largest tires for 3" lift

I have a 4" lift and have 20x12 -51 offset with 305/50r20....

 

I understand the aesthetics of moving to larger tires. They give you a little boost in altitude and look good. But as mentioned in other posts, I'm a "form follows function" kind of guy. In other words, I don't mod for looks. I need a justifiable performance gain to validate the $$ and effort to make a change.

So the two part question is this...
How MUCH performance gain do you get off road going from a 30.6 inch tall tire to a 33.0 inch tall tire? That's a 2.4 inch gain but only half of that is on the bottom side of the wheel. You only get 1.2 inches of tire lift. When we look at the contact patch, that 2.4 inches of tire gets you an 8.2% increase in Circumference, so I'd guess (not an engineer by far) that gets you roughly 10% more contact patch - give or take.

But now that upgrade in tire size also get you issues with:

• Speedometer - 60mph is really 65mph.
• Odometer - You think you are doing 5,000 mile oil change intervals but they are really now 5500 mile intervals and your distance to empty is off.
• Miles Per Gallon - Worse because you are slinging more rubber around and because your calculator is off (see odometer)
• Transmission shift points & drive-ability.

Each person has to determine if the issues are a problem for them and if they can tolerate them or if they are willing to correct them and to what degree, but they do show up for everyone. So does the larger tire size get you any measurable increase in performance and if so how much and is it worth the trade offs above? I know a lot of people here will knee jerk "Hell Yeah it's worth it!" and I get that. I want larger tires too.

Here's the rub... And not a tire rub either. My current stock size haven't let me down on the trail. I can't measure a larger tire performance gain over stock, because I haven't had a stock performance failure. Some times 8% to 10% is all you need to make it past that point where the other tire didn't make it. I just haven't found that point yet.

I think for me the justification would be in a softer less punishing ride on our hard scrabble rock strewn mining roads at around 30 to 35 mph. The same 18psi air down would have an extra 1.2 inches of tire bounce travel to soak up a bump.

But I'm not looking at 255/85-16 (33"). I'm looking at 265/75-16 (31.6") because I want to stay with BFG ATKO's and stock wheels. That gives me .5" of more cushion. Arguably much less impact on the Speed / Odo / Trans mentioned above. But now I have to ask is that 3% tire size gain going to even be worth it?

 

Like I said, I didn't make that graphic...don't overthink it