Just a quick image and update. 33" tires on 18" LR3 wheels INSTALLED and functioning properly.
This image shows the LR4 in "Normal" suspension mode. "Off-Road" would give another 2"+ of chassis clearance. The suspension is adjusted with Johnson Rods, giving 60mm (2.5") above stock. Then I added another 10MM to the rear only, using the IIDTool. That is what this image demonstrates.
The 33" tires fit and rubbing only increased slightly, particularly at the frame horn just aft of the front tires. We are going to laser cut that panel and reweld with more clearance. The tire also rubs slightly on the ARB bumper and where the fender liner interfaces with the back of the bumper. Both will be easy to trim and clearance. In the rear, the tire rubs on the pinch weld and fender liner forward of the rear tire. It also rubs slightly on the rear HVAC lines. I actually do not see this as a big issue, as the rubbing is quite light and the lines are aluminum. Further investigation reveals that new lines could be made and relocated. We are going to monitor this as use continues.
The Falkens are pretty ideal for this truck, running smooth on the highway but have a few important construction features that allow fitment. They are tall and narrow, measuring 33" tall X 10.5" wide. They are narrower than the Mickey Thompsons we removed by 10mm, but more importantly the carcass has a notable radius at the shoulder and limited edge lug elements and features. This smooths any rubbing and helps with clearance. The 1.25" spacers also seem to help with clearance, particularly at full lock against the frame. The spacers also restore the lost track width from the suspension lift and add about 2" to the total track width, compensating for the additional tire and suspension height. The spacers keep the tires just inside the fender flares, so it doesn't look odd.
MOST IMPORTART!
Anyone that owns an LR4 can install 1.25" hubcentric spacers and use factory LR3 18" wheels with no further modification. Using a 1" spacer would require some grinding of the caliper. Use no spacer requires significant grinding of the caliper. This will save (potentially) thousands over specialty 18" wheels. We found these LR3 wheels used and only had to purchase a new spare wheel to match. Total investment was less than $1,000 to have 18" wheels.
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This image shows the increase in track width from the 1.25" spacers. These tires are 265 wide. It looks correct and not goofy (i.e. sticking out past the fender flares).