Originally Posted by 2013gs350
same here 3rd set of 20's on the rear to 1 set on the front
So I've been looking for a new set of rear tires and found the difference between the two different Michelin PSS tires both is size 285/30-20, a K1 and a regular version. This probably explains why you're going through these so fast.
You probably has the K1 spec tire made specially for the Ferrari. As you noted brand new they have 7/32" of tread, compared to the 'regular' version which has 10/32" of tread. So right off the bat you're down 30% in thread wear. The K1 also has larger groove between the threads. Hence the K1 version only weighs around 24.5 lbs while the regular version weighs 27.5 lbs (still very light for this size). Finally the K1 has slightly curve/rounded side wall while the regular version has a lightly square side.
I was able to find a pic of those two tires side by side over in the BMW forum. K1 version on the left, the regular version are in the middle and the right. Both are 285/30-20.
Needless to say I was able to find a set of regular brand new 285/30-20 PSS from craigslist of all places, since the PSS are on back order right now. That and also most tire stores only list the K1 tire version. I'll have them mounted this week so I'm crossing my fingers that they don't rub. I am currently running Michelin A/S Plus in size 275/30-20.