TJ, Thank you for responding. I am not clear on what you mean by "Sometimes". Do you mean that some Xterras have bottoming out problems while other do not?
Secondly, if I add the equipment you suggested, what will that do to the warranty?
Sometimes means that its related to your individual truck's unique attributes...IE: They're all a bit different...and some have stronger leaf packs, or weaker, etc...and carrying a heavy load is going to exacerbate your own unique circumstances.
I think that when they did the mathematical rollover calculations, they lowered the ride height a few cm to get under a threshold/break point for COG, and didn't change other factors to compensate for the loss in room for uptravel.
That means that up travel is shorter on room than originally designed...but that you have more down travel proportionally, etc.
The Timbren bump stops, etc, should not impact your warranty, as they will not really have a way to damage a covered part.
To deny warranty coverage related to a modification, a maker has to PROVE that the modification CAUSED the covered part(s) to fail.
So if you attached a 10,000 lb HAM radio transmission tower to the rear bumper, and the bumper fell off, they might be able to show how the added weight pulled off your bumper.
If you put a squishy progressive bump stop on, so that the rising axle impact was cushioned and softly absorbed on its way up...what would that break exactly?
So, no one I know has had that sort of warranty problem...and, if they did, they are at least protected by law against denial.
Essentially, there are NO modifications that "Void your warranty"...only coverage of an individual covered item.
The people who do get arguments are those who've made a change that at least COULD theoretically caused the damage, say putting 37" tires onto the stock front axle...and blowing a front diff. Its possible at least that the added forces a larger tire imposes would add stress on the differential...so an argument at least has some validity.
On the flip side, most people get covered for that stuff too, it depends on the personality and culture at the dealership, etc.
So, no warranty problem for the anti-bottoming stuff....it helps rather than hurts.