fitment request

taking delivery of a c320 soon and have done much research on the tire question, benz canada and all the experts tell me that the largest you can go to is 225/50 as fitted on the sport package, you can put 225/50 on the elegance too as all c class have 7x16 size wheels, if you fit 225/50 the error is .06% and the maximum permissible error is 5%