To compensate for the heavier tyres to be used this season, the FIA has increased the minimum car weight by 6kg.
Article 4.1 of the Technical Regulations (pdf) issued on January 24, states that: "The weight of the car, without fuel, must not be less than 722kg at all times during the Event".
However, Article 4.3 also states that: "The weight limits specified in Articles 4.1 and 4.2 will be adjusted up or down according to any differences (rounded up to the nearest 1kg) between the total set and individual axle set weights respectively of the 2016 and 2017 dry-weather tyres.
It is understood that the difference between the 2016 tyres and their wider 2017 counterparts work out to just over 5kg a set, which when rounded up (to 6kg) means that the minimum weight increases to 728kg.
This compares to a limit of 702kg in the 2016 regulations.
Other than the wider tyres, bigger fuel tanks are required this year (hence more weight) after the fuel limit was increased to 105kg from 100kg. Another factor is the new wider cars this year, which see an increase of 20cm compared to 2016.