Hi,

Earlier this year I bought a 2026 Octavia IV RS Combi, and it came with 225/45 r18 summer tires.
It's this time of year that I have to start thinking about getting a winter setup.
I've noticed that even current gen Golf's use 225/40 R18 tire size, and quite a lot other cars do as well.
I've also noticed that 225/40 R18 size has much more new premium tire models available (like Michelin CrossClimate3 Sport, or Goodyear Vector All Seasons 4),
while they're not available in 225/45 R18 size. And interesting tires that are available in both sizes, like Pirelli SF3 are exactly 50% more expensive in the 45 profile compared to 40 profile.

Needless to say, I see a lot of benefits of going with th 225/40 R18 for my winter tires setup, but that will give me over 3% smaller wheel diameter.
Therefore does anyone know if that will work?
Won't abs/esp go crazy?
Is it possible to modify the wheel diameter in the car computer using a new OBD Eleven interface perhaps?

If the tire size is not specified in the car's official papers (e.g. Certificate of Conformity), just don't use that size - there are plenty of reasons for that.
BTW - if you're looking for a winter setup, why are you searching for All Season tires?

All Season 3PMSF (Three Peak Mountain Snowflake) tyres might be all that is needed if you do not require FULL SNOW Tyres. Plenty All-Seasons suitable for use in Snow or pisted or non pisted roads and even if Snow Chains are needed. @Mariosti The ABS / TPMS / TC will not give a monkeys if there are different widths or circumference of tyres fitted. Reset the TPMS. But you are intending changing the Diameter / Circumference. Maybe just fit narrower treads / sidewall to sidewall if cost is an issue. Set your Winter Tyre speed warning on the car if Winter / Snow Tyres are fitted.

Edited 6 minutes ago6 min by Evolution13