15" Yokohama Avids on my Pearl IV. The dealer had different tires on different Prius' onsite... there wasn't really any rhyme or reason to it...
Got it today! Oh - Yoko! How John Lennonish. For now, they will have to do, they are round and black. Totally stock II in Black/Dk.Grey. Actually, bought the car to transport my HPVelotechnik recumbent trike. Prius replaces a 2005 Jaguar X-Type which carried the trike on a home made hitch rack in back. Or, as I saw it, a $5000 trike protecting a $5000 bumper. Stupid of me, should have bought a Prius in 2005, but then, I wouldn't be getting a 2010, would I? Now, I feel better!
Took delivery of a 2010 Prius V on 7/31/09 that had been received by the dealer on 7/30 with Toyo Proxes A20 P215/45R17 87V tires. They seem to be completely acceptable so far on both wet and dry pavement but I can't find any test data on them.