The Mercedes CL tyres offered at Tyres.co.uk include Michelin Primacy 5 and BFGoodrich Advantage 2 in 255/45 R18 99Y. This is a factory fitment for the C216 CL 500 and CL 500 4MATIC. Please ensure you supply your registration as other models/wheel options have different pairs for front/rear.
The tyre pressure table in the vehicle's fuel filler area (on the rear-right side) shows the correct sizes of the tyres for the Mercedes CL. The tyre pressure table shows the appropriate combinations of wheels, tyres, and pressures approved for the vehicle. Refer to the tyre sidewall and the handbook, as specs and wheel options will affect different generations of the vehicle.
The Mercedes CL does not require the replacement of all four tyres. You need to replace at least one of the pairs on the same axle and maintain the factory staggered fitment. For the CL 500 4MATIC, you need to use the same type of tyres throughout the vehicle, so either match the pair or replace all four. When replacing a pair, the recommendation within the scope of UK tyre safety is to fit the new tyres on the rear axle.