275/65R20 vs 275/75R17 is the swap people make when they drop from a 20-inch truck wheel to a 17. Same 275 mm width. The 65 on a 20 and the 75 on a 17 land in the same height band: 34.1″ vs 33.2″. Compare them live: 275/65R20 vs 275/75R17.
The two stamps
| Size | Diameter | Width | Sidewall |
|---|---|---|---|
| 275/65R20 | 34.1″ | 10.8″ | 7.0″ |
| 275/75R17 | 33.2″ | 10.8″ | 8.1″ |
Diameter moves -2.4%. Width does not move. At 60 indicated on a truck calibrated for the 65, the 75 is doing 58.5 mph actual. That is a speedometer non-event. The real change is the rim: three inches less wheel, more sidewall, a different ride.
Why this pair gets searched
People type 275/65R20 in inches and get sent to a comparison with 275/75R17 because the two stamps answer the same height question on two popular truck wheels. The 20-inch 65 is common on late F-150 and Ram packages. The 17-inch 75 is the older, cheaper wheel that still clears the same well.
If you are staying on 20s and only want height, the 275/65R20 vs 275/60R20 page is the same-rim version of this argument.
You cannot put a 17-inch tire on a 20-inch wheel. This pair is a wheel-and-tire swap, not a rubber-only swap. Budget the wheels.