1. the 255/65 isn't really what I would call low profile, it has a taller sidewall than anything on a stock Jeep. 1 265/75-16 will put you at 31.6" which will fit with some modifications to the plastic trim around the wheel wells.

2. Oversizing a tire on any vehicle will decrease performance. Your SE should be geared at 4.636 ring and pinion. The Xterra is weak in the transfer case, with only a 2.01:1 low range ratio.

3. I'm on my second set of springs in 20 months, and they have already sagged 2 inches in 6 months. I'm looking for a better solution.

4. About an inch. Get a factory manual if you want to keep it within specs.

5. No problems yet.

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Regards,
Ian