With the imminent arrival of the new 2023+ FL5 Honda Civic Type R here in the US, it was only right for us to document in detail our procedure for wheel fitment on this new chassis. This database will serve as a resource and helpful guide for those who plan to modify their 11th Gen Civic Type R.
Shown below is our friends in Japan with the new FL5 11th Gen Honda Civic Type R test-fitted with Rays Volk TE37 in 18x9.5 +45, 5x120, paired with Michelin Pilot Sport 4S in a 265/35/18 squared sizing. The factory wheels are 19x9.5. Downsizing from the conventional factory 19's to 18x9.5 wheels with a +~45 offset will prove advantageous for those who are looking to increase ride quality, reduce unsprung mass, and increase overall driving dynamic. Going to 18's will allow one to also run better compounds on the street / track. The OE tires are 265/30 on a 19x9.5, and very much like the previous generation, the sidewall is a bit thin on the factory tires. Going down to an 18x9.5 +~45 will enable one to run a 265/35 or even a 265/40 tire for improved ride quality. If one is looking to fill the wheel gap more, we recommend going with a 265/40 on an 18x9.5.
Update: 11/11/2022: It is also worth noting that we test-fitted 18x10 +~41 with a 265/35/18 Falken tire. The 18x10 +~41 comes out ~10mm more outward compared to the 18x9.5 +45 (which is flush). This means the 18x10 +41 pokes a bit and definitely requires fender work on the outside to mitigate or reduce the chances of rubbing. On the inside, the 18x10 +~41 loses about ~2-3mm of inner barrel clearance and this actually becomes an issue at full compression/full lock and will rub the fender lines more than the 18x9.5 +45, which seems to be the happy medium. An 18x10 +~40 will gain about ~1mm of inward clearance and should be a bit better, but on the outer edge it is still ~11mm more outward compared to the 18x9.5 +45.
At the end of the day, we are finding that the tolerable sizing window falls between +~43 to +45 offset for a 9.5 inch wide wheel with no issues, up to a 265/35/18. There is no need to go up to an 18x10 or 19x10 if you plan on running a 265 tire. A 275 would definitely rub the outward fenders, if not rub the inside, as you are effectively losing ~6mm of inward and outward clearance compared to a conventional 18x9.5 wide wheel. At 18x9.5, you are able to run a 265/35/18 or 265/40/18, 255/35/18, or even a 255/40/18 tire without issue. Those who wish to "fill out" the wheel well more should go with a 265/40/18 or a 255/40/18 tire with a larger sidewall.