I haven't read it yet, but, historically wheels and motor (aussie magazines) haven't always been correct in their facts.
But yes, needs to be low 1400kg for me.
What is your 1500kg source? There has been no official comment from Toyota on mass of the vehicle.
This is the most reputable leak/rumour on weight:
http://club4ag.com/a90-coming-along-seems-first-reveal-goodwood-festival-speed/
"Front Tires. Pretty large set of tires for a car with such...