Replaced OEM Continental 4x4 Contacts. Sumitomo is ill-suited for R350's combination of weight (5,000 lb) and suspension/chassis/handling characteristics. Sumitomos borders on UNSAFE! Sheer lack of steering response @ hwy speeds! Slightest steering correction (follows ruts like any fresh tire) results in (1) momentary delay, followed by (2) front end dive/veer, then (3) excessive rear kick-out/sway. And all this despite recent alignment. W/ 30 yrs experience driving both hi-performance and family European vehicles, I can reasonably conclude that the Sumitomo's lack of sidewall stiffness and slight added weight (37 lb vs 35 lb for Continental 4x4) mate poorly to weight/chassis/suspension combination of R350. I agree w/ other noted respondents and family friends that the OEM Continentals have below average tread life. But in retrospect, the OEM Continentals exhibited a very good combination of sidewall stiffness, grip, and ride quality, which understandably can be difficult to satisfy in 5,000 lb crossover vehicle. I'm very concerned over the Sumitomos; so much so that I have swapped vehicles w/ my wife. I will monitor the tires, and if they do not improve following a reasonable break-in period (say 1,000-1,500 mi), I will have to replace them, despite hurting my pocketbook.