Fitment options for the Fiat 500X on Tyres.co.uk list the Michelin Pilot Sport 5 and Goodyear Eagle F1 Asymmetric 6 in 225/45 R18 95Y XL. These are some of the replacement options for many units that have the factory 225/45 R18 91Y tyres. Please check other details on your Vehicle Registration related to wheels such as wheel dimensions, load index, and speed rating before ordering.
The tyre size for the Fiat 500X can be found on the driver side of the B-pillar and on the tyre and pressure label. The recommended pressure tyre label also specifies the load and speed ratings of the tyre. When looking at the sidewall of the tyre and comparing that to the vehicle registration, just remember that there are other variations and thus other configurations of wheels.
The Fiat 500X, as a general rule, does not need all four tyres replacing, as long as a new axle pair matches the other axle; UK tyre safety guidance is to fit the new pair to the rear axle. Fiat specifies the same make and type on all wheels, and for 4x4 variants, the same size, type, and rolling circumference must be maintained.