If you own an F8 and have tried using 25mm or larger tires then you might have run into an issue with the tire rubbing on the underside of the rear brake caliper. Your frame is not defective it's simply a design oversight on Pinarello's part. The F8 was released in 2015 but designed in the later half of 2014 and at that time most pro cyclist were still using 23mm tires. The rear brake position was designed to be as low profile as possible which unfortunately cuts things real close for today's larger tires and wider rims.
Current model Campagnolo, Shimano and SRAM calipers were designed around the same time and suffer the same fate. They don't accommodate larger tires on certain frames. There is very little one can do other than move to a smaller tire or modify either frame or rear caliper which is potentially dangerous and voids warranty.
Good news is on the way. Shimano's new 2017 9100 Dura Ace brake calipers are designed to offer more clearance. See image below (credit cyclist.co.uk) how it offers just a few more mm than the 9000 and allows for a 25mm to be used on the F8
Buy yours here: we have them available now.