Subaru Outback tire size is mostly 225/65R17 or 225/60R18. Base, Premium and Wilderness 17-inch packages wear the 65-series. Limited, Touring and many Onyx XT 18-inch packages wear the 60-series. Width stays 225. Wilderness is a tougher tread and a higher load, not a different diameter class.
Stock sizes by trim
Sixth-gen Outback (2020+) is this table. A 2018 Outback used 225/65R17 on a lot of trims as well, so older cars often still match. XT vs non-XT does not pick the size. The wheel does.
| Trim / package | Stock size | Wheel (in) | Diameter (in) |
|---|---|---|---|
| Outback / Wilderness 17-inch | 225/65R17 | 17 | 28.5″ |
| Outback Limited / Touring 18-inch | 225/60R18 | 18 | 28.6″ |
Why the sticker beats the chart
Subaru AWD wants matching circumference at all four corners. That is stricter than a two-wheel-drive Camry. If you replace two, replace four, or put the new pair on and accept that you are close to the wear limit the manual already warns about. Mixing tire sizes is the short version.
A Subaru Outback can leave the factory on more than one size. Export markets, mid-year packages and previous-owner plus-sizes all disagree with a chart. Read the driver-door placard. Match width, aspect ratio and rim together.
Swapping to a different size
225/65R17 is about 28.5 inches. 225/60R18 is about 28.6. Factory plus-one. A Wilderness owner who wants more height is asking a crossover to be a Tacoma. Stay near 28.5 unless you have measured the well and accepted the speedometer error.
Wilderness is a load and tread change
The Wilderness 225/65R17 is often a higher load index and an all-terrain tread on the same geometry as the base 17. Replacing it with a highway 225/65R17 matches the stamp and can drop the load rating. Read the placard load index, not just the size. Load index is that table.