305/60R20
305/60R20 is uncommon as OEM fitment but appears as an aftermarket upsize option. At 34.41″ diameter with a 7.20″ sidewall (60% of section width), this size turns 586 revolutions per mile.
About 305/60R20
305/60R20 is less common as a factory fitment but is available as an aftermarket size, so SKU selection is narrower than mainstream OEM sizes. At 34.41″ overall diameter, 305/60R20 turns 586 revolutions per mile, which is the reference point the factory speedometer and odometer were calibrated against. The 60% aspect ratio gives it a balanced sidewall — enough compliance for daily comfort without vague steering. The 20″ rim pairing is typical for luxury SUV and performance-oriented platforms, so compatible wheels are easy to source new or used. Going one step shorter to 295/60R20 drops diameter by 1.37%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 285/65R20 adds 0.51% diameter — also inside the safe window, with marginally taller ride height. If you are shopping for a direct replacement, any tire within roughly ±0.7″ of the 34.41″ stock diameter (about ±2% in percentage terms) will keep ABS, TPMS, and odometer readings inside the vehicle's designed tolerance.
Compare with another size
275/65R18 or "33" for inch aliases305/60R20
- Diameter
- 34.41″ / 874mm
- Section Width
- 12.01″
- Sidewall
- 7.2″ / 183mm
- Circumference
- 108.1″
- Revs/Mile
- 586
285/60R20
- Diameter
- 33.46″ / 850mm
- Section Width
- 11.22″
- Sidewall
- 6.73″ / 171mm
- Circumference
- 105.13″
- Revs/Mile
- 603
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 58.35 mph (93.91 km/h). Your speedometer reads 2.75% high versus actual speed.