Firstly, sorry for digging up this oldish topic. I am a new member and I browsed this forum a lot (found a lot of helpful information) when I was planning to order the car in 2006.
Just recently I noticed that both outer sides of the front tires are substantially worn. I thought it was down to overly high cornering speeds. But the other day I found one of the front tires flat while the car was sitting in the parking lot. Turns out, the inner sides of the tires were worn even more badly, so on of them had torn and didn't keep any air in it. This was surprising especially as the centres, where the wear indicators are, still had 3-4 mm of tread left. I have always kept the tires inflated to the recommended specs, so I will outrule underinflation.
The workers at the tire shop said it was nothing new to them, and they had had several Lexus, BMW and Mercedes owners with the same problem. Just my theory, but can it be that when you turn the steering wheel all the way to the left/right, the front wheels tilt a bit to help decrease the turning circle, and such a wide and low profile tire doesn't flex enough and simply wears out the sides it's on? (Most RWD luxury cars should do this tilting thing, right?) Oh yeah, I have the 17" 225/45 fronts; 245/45 rears. If this theory was indeed the case, the 18s would wear even faster, wouldn't they?
Seeing as the center part still had plenty of tread left and the rears have worn perfectly evenly and still offer plenty of grip even after 55 000 km (and 2,5 years), I was just a bit shocked to be throwing away what at first looked like perfectly usable tires.
2.4 bar front and 2.6 bar rear is already a high enough number on the border of stiff. After this I have tried increasing the pressures in the fronts to 2.6, but they became a bit too bumpy and lost too much grip as well. Considering the roads I have to travel daily, that isn't really an option. Furthermore, I rarely ever exceed the 160 km/h speed that Lexus has recommended an increased tire pressure for.
I am not saying that getting so many kilometres out of the original tires (Dunlop SP Sport Maxx, which were amazing both on tarmac and surprisingly gravel) is not great, but still it makes you wonder if there is anything to be done to avoid wasting tires like this in the future. (adjustments to the undercarriage or whatever)
I am no engineer or mechanic, but still I hope to receive some helpful comments while avoiding hateful ones.