+Tire Diameter 4 Better Look/Lower RPM

[JCL]

1. Is the large clearance between tire and fender necessary?

Only fitting by trial and error will determine if you will have sufficient clearance.

2. Larger tires = Lower RPM. . . . but are there any damaging repercussions if the OBC is NOT reprogrammed for the new diameter?

Not to the OBC. Your odometer will read under the actual. The speedometer won't be out as far, as it is optimistic to start, by design.

Apart from the OBC, you will have some negative effect of such a heavy tire. Consider the increased wear on suspension components, and inertial effects of the increased tire at that position on the rim, which will mean slower acceleration and braking.

3. Transfer case considerations - would it be prudent to find a tire combination for the set that starts with a SLIGHTLY larger diameter in the front? Thus the fronts could wear down to equal diameter . . . and then only approach a diameter disparity limit when the set of four is due for replacement . . .

No. Always try for matched. Don't expect that they are going to wear down evenly in any case.

[DSAviate]

I always appreciate your feedeback JCL.

My experience has been that the front tires wear more than the rear. I know this is subject to driving habits . . . but the fronts are subjected to the demands of turning friction and the lions share of the bracking friction.

If I always start with equal diameter tires in a staggered set, I'll expect the fronts to be done when the rears still have ~ 50% tread left. Has anyone here experienced otherwise?

[JCL]

Originally Posted by DSAviate

If I always start with equal diameter tires in a staggered set, I'll expect the fronts to be done when the rears still have ~ 50% tread left. Has anyone here experienced otherwise?

Haven't used a staggered set up, but both my X5 and X3 wore four tires evenly over 75,000 km (original tires in both cases). The X5 tires were still in good shape at that point (sold the vehicle). The X3 tires were replaced at 4/32", not worn out, but I wanted to replace them for another reason. I would have gotten 90,000 - 100,000 km on them, by my calculations. I never rotated tires on either vehicle.

Wearing fronts out first isn't from braking, it is from aggressive cornering with a heavy vehicle, so YMMV.

[DSAviate]

Based on all research and feedback, now looking at the following tires for my offset 87s:

General Tire Grabber UHP -

Front 275/45 R20, 29.7" diameter
Rear 295/45 R20, 30.5" diameter

Will these .8" larger diameter rear tires place any inappropriate stress on my Mechanical transfer case (NV 125)?

It seems to me the transfer case must be designed to accommodate slightly different rolling diameters front to rear. Is this not true?

[JCL]

685 revs per mile vs 699. I would try and get it closer than that.