Gloonyx

The OEM tire size for A250 is 225/45/18. I would like to increase the width to 235/40/18, which is A35 AMG OEM tire size. Has anyone upsized to wider tires? Any rubbing?

aj240

225/45/18 = circumference of 2072mm, Side wall Height 101mm,
235/40/18 = circumference of 2025mm, Side wall height 94mm.
235/45/18 = circumference of 2101mm, Side wall height 106mm

Based on the figures above you would see a decrease in side wall height for the 40 profile with an increase of width of 5mm on either side of the rim, I doubt this would cause rubbng, but you will also see a decrease in accuracy of your speedo ! This due to the decrease of circumference.
If however you went to a 235/45 you would see an increase in wall height of 5mm (10mm vehicle height) I doubt this would cause rubbing as there is still plenty of room. You would also see an increase in accuracy of the speedo as by default most speedo's read under the real(GPS) value.
I had this same scenario on another vehicle and had an accuracy increase whereby my speedo is now within 1km of GPS values.

Hope this helps

jastleymb

I did measure the fender clearance (inside top of fender sideways to vertical line from sidewall) on my A250 and it is only 15 mm. with OEM 225/45-18s. At 10 mm. clearance for your proposed tires, that seems fairly small. In dynamic conditions I'm not sure that would be quite enough margin

Gazwould

Tyres vary in width and aspect ratio size from make to make so take calculations with a pinch of salt.

My father went from 225 45 18 to 245 40 18 on a non MB car and it's worked out well .

Nice size tyre , good width with enough profile to still be direct and soak up the bumps .