Thanks for your information, nice, that you could arrange a deal with M DT......, i can´t show the change from back to front each 6k range. But what i can confirm is that the pressure with 38psi(2.6bar) is definitly to high for the S60, you see that in the middle of the tire more arbrasion, you really should as you noted take about 36psi. Really bad that P did not recommend always the best for the car, so i think a PZEROTM will perform much better on this car with 36psi....FYI,
If you want to claim warranty on your OEM Michelin tire the key factor is that the tire wear be some were below the 3/32 or 2/32 on each tire. My tires were at 1/32, two of them at 2/32 and one at 3/32. You also have to show that tire rotation was done within the 6 -8k range. In my case, I am somewhat anal retentive with logging my service, so no problems with that. I only got two rotation out of my tires 7500 and 14900. The DT manager was indicating to me that all the tires had the center treads worn out, which he claims it towards tire over-inflation. I explain to him that Volvo claims that we need to run these tires at 38 psi. He was recommending to lower my tires to 36 or 37 psi to prevent the center tread wear. The s60 feels much better now and no more front wheel hopping while making tight turns into my driveway. Manager at DT also gave me a Michelin rebate form for $70 so the final price with the mail in rebate discount card was $558. Is not a bad deal, but definitively I need to find another tire option down the road for this car.