You missed one important point - your alloys are 7.5J on the front and the C63 is 9J , you won't be kerbing your alloys with those tyres sticking out over your rims.Many thanks for your input matey. So I did a comparison on tire ratio and all on different sizes vs mine and this came up. Now my brain is ADHD build and I have math dyscalculia so my brain works maths differently in a work it works for me to tackle it and understand the best it can thats why I cant work it in my head like comrades doing here if this increases and that increases than that too increases, that whole mental picture of it my frontal cortex cant visualize step by step as brain struggles to comprehend. as soon as its numbers. My apologies as I come across daft in math's department. Calculators helps with ADHD mind greatly.
The least change I can see is the bottom spec vs 1st spec which is what I got on right now so 1.5 mm vs 5.5 m is the least difference and that was achieved if I drop the front aspect ratio to 35 from 40. I dont know why MB kept 40 aspect ratio in front on mine and 35 on rear where as standard C63 for example is 35 in front and 35 in rear. What possibly could be reason or advantages for this mismatch MB did I wonder 40 in front and 35 rear. Thinking about it now perhaps 35 in front and back all the same would have been better you think ? Please share your thoughts. many thanks again.
so according to the calculator link you send me for my C300 spec is:
Comparing 225/40R19 against 255/35R19
Width Profile Rim Diameter Diameter
Tyre 1 225 40 19 662.6mm
Tyre 2 255 35 19 661.1mm
FITMENT OK!
The percentage change is 0.23% and the circumferece change is 1.5mm.
and below are different specs
Comparing 245/40R19 against 265/35R19
Width Profile Rim Diameter Diameter
Tyre 1 245 40 19 678.6mm
Tyre 2 265 35 19 668.1mm
FITMENT OK!
The percentage change is 1.57% and the circumferece change is 10.5mm.
Vs
Comparing 245/35R19 against 265/35R19
Width Profile Rim Diameter Diameter
Tyre 1 245 35 19 654.1mm
Tyre 2 265 35 19 668.1mm
FITMENT OK!
The percentage change is 2.1% and the circumferece change is 14mm.
Vs
Comparing 225/40R19 against 265/35R19
Width Profile Rim Diameter Diameter
Tyre 1 225 40 19 662.6mm
Tyre 2 265 35 19 668.1mm
FITMENT OK!
The percentage change is 0.82% and the circumferece change is 5.5mm.