In 235/55 R18 104V XL, Tyres.co.uk offers Michelin CrossClimate 2 and Continental PremiumContact 7. These tyres will fit your 2008 Lexus RX 350, which comes equipped with 18-inch wheels, as long as you check the size against your wheels and keep the load and speed ratings in line with your registration.
The info you are looking for regarding the size of your Lexus RX 350 tyres can be found along with the other important info, like load and speed rating, and the recommended inflation pressure on the Tyre and Loading Information label, which you will find on the door jamb of the driver’s door. Make sure your measurements are based on the information provided on the label rather than on the sidewall alone.
Lexus policy states that, although Lexus RX 350s do not always need four new tyres, new tyres must be of the same size, load capacity, and tread pattern, as well as the same brand as the other tyres, for safety reasons especially of the AWD versions. When the original tyres cannot be matched, all four must be replaced. Where they can be matched, the new pair should be installed on the rear axle, in line with UK guidance on tyre safety.