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Actually, it isn't the same. From what I'm reading you purchased RRS tires/wheels, then replaced the factory tires on the Sport wheels with direct replacements. A 255/60R18 (standard LR3 tire) comes in @ 763 MM, (30.03 inches) While stock RRS tire is 255/50R19, which omes in @ 737 MM, (29.01 inches). The stock LR3 size is 255/55R19 (762.5 mm). Your vehicle just lost 1/2 " ground clearance.The height is exactly the same so I won't need to have the computer updated. Next service I'll have them make sure the senors are being picked up by the computer as I did not get that option when I purchased the car.
What'd you do with your old rims?
The load index on the OE RRS tires are significantly lower than the LR3's, hence you have decreased the GVWR of your truck. Which should be no problem unless you loading-up your LR3 or towing. A few folks on Disco3 have experienced sidewall failure with this combo however. Those Conti's will wear-out in no time, so you can replace them with a tire with the appropriate LI.
I should have kept them to sell but felt lazy. I gave them to the shop that mounted the new ones in exchange for credit of $40.00.