Selecting the right wheel size

[Star_see]

Hi guys,
Hoping someone could assist with this. I’m replacing the original boost wheels on my 2016 D90. I haven’t decided whether I’m going 16 or 18 inch wheel. 255/85 or 275/70 but I’m having trouble picking the right offset.
I want the the outer side of the tread to sit flush with outer side of the guard and I don’t want to replace the fender/guard with bigger ones.
Is the right offset 0 or -6
Appreciate any guidance
Thanks

[100inch]

I am running 255/85R16 on Sawtooths, which have 20mm OS. Perfect combination, as 0 OS stands out too much. You can run Boosts as well with 255, as the 90 has smaller rear springs, but you probably need to reduce steering lock. m

[MLD]

rule of thumb is zero offset for 255/85. others have had success with a positive offset rim but zero will give you the turning circle, not rub and fit under the guards. Not sure about neg 6 fitting in guards. Its bugger all and likely lost in the variance of tread patterns between tyre manufacturers. law says so long as the flare covers top tread width of tyre, ie flares that taper back to the body are fit for purpose even if the tread at the 3 and 9 o'clock is outside the line of the flare.

One thing to consider is flick up. more the tyre sticks out from the body, more mud, water etc flicks up on side of car and window. I've had to wash my door handle on many a muddy trip.

[100inch]

Hmm, I had definitely rubbing with 0 offset. Also 0 OS ruins (well, adds) your scrub radius even more. m