Originally Posted by BreakPoint
Federer probably customizes his K90 with lead tape underneath the bumper guard, that's why it probably feels heavier even if you can't "see" the lead tape.
BTW, my retail K90 weighs 13.2 oz. stock with just two thin overgrips on it, so I don't know how much heavier Federer's K90 can be. I mean, he swings with such massive racquet head speed, I doubt his racquet can be that much heavier, especailly when he seems to be able to swing just as fast after playing against Nadal on slow red clay for grueling 5 sets and 5 long hours.
Yup , thats why I was so surprised . & yes , his racquet head does seem to be very fast on clay - maybe he changes specs on clay - but look at dubai open , he has a shorter swing more flat.