Agree with @Carlston You're maybe thinking of the common Mk3/3.5 move from 225/40R18 to 235/35R19 - in which case, yes, a drop in profile is needed. In order to drop down to a 35 profile, you'd want to be moving to a 255 or even 265 section. Similarly, to go up to a 45 profile, you'd be wanting a 200 tyre - it's quite a big difference! 235 is the maximum tyre that can fit on a 7.5J rim. It is recommended to have a 215/225. You don't want to be doing maximums or minimums for anything tyre related. On a 7.5J, a 205 will be stretched which will cause issues. 235 on a 7.5J is approaching instability territory IMO - the sidewall of the tyre is having to do more work. For a 235/245 section tyre, you're better off with an 8.5" wheel IMO. Some cars (Karoq, etc) have 19x8" wheels, but AFAIK the Octavia is a 19x7.5". Lot's of people put 235s on a 7.5J wheel - be it on a Cupra, GTI, R, S3 or whatever, but that doesn't mean it's right. There's a reason VW ships the cars with 225. You won't notice the difference going from 225 to 235. Go from 225 on a 7.5J to 245 on an 8.5J and yes, there'll be a change - and not always a good one. TLDR - absolutely increase tyre width if you want better grip, but you'll need to increase the wheel width to suit. @OP I would stick with 225/40R19. You aren't going to get anything that offers any benefit - stick some nice PS5s on it instead.