2025 GX 550 OT plus (1 Viewer)

[JeffS]

Can I use 285/75/18 KO3’s without modifying? What about the spare? Thank you

 

[DJ’s Sled]

Others can answer your “without modifying” question. Your situation is different from mine.
(I have a 2024 with a lift kit, and am running a ‘shy’ 34” tire, 285/70/18 with a +25 offset wheel. The tire measures at 33.7 diameter..without need for any trimming or rubbing.)

For my spare I’m using a ‘tall’ 275/70/18 tire fully inflated, which also measures 33.7 diameter, and it fully fits up into the spare location. It’s extremely tight, it touches all 3 or 4 seating tabs; but it is fully seated with no space, zero, remaining.

So, maybe.. you can squeeze your 285/75/18 of choice up there uninflated, without any real issue re-inflating by yourself if ever required. I think someone else on this forum has stated that. The KO3 you mention is stated as a 34.8” diameter.
Others here with more experience can weigh in.
I also don’t know if the 2025 spare tire space is exactly the same dimensions as my 2024?
Good luck, and welcome to this excellent forum!