What sizes can I use ?

[Pitsmoor Col]

I currently have 225/50/17. front and rear. Must I stick to these sizes or is there some other size I can use ? Car is C Class 220 blutec auto W205.

 

[Blobcat]

What's listed in the manual and/or fuel filler cap?

 

[JBell]

From that tyre size all round I will assume you have the same size wheel all round so unless you buy wider rear wheels you are stuck with the tyre size you have