305/60R18
305/60R18 is uncommon as OEM fitment but appears as an aftermarket upsize option. At 32.41″ diameter with a 7.20″ sidewall (60% of section width), this size turns 622 revolutions per mile.
About 305/60R18
305/60R18 is less common as a factory fitment but is available as an aftermarket size, so SKU selection is narrower than mainstream OEM sizes. At 32.41″ overall diameter, 305/60R18 turns 622 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 18″ rim pairing is typical for full-size truck, premium SUV, and sport-sedan platforms, so compatible wheels are easy to source new or used. Going one step shorter to 295/60R18 drops diameter by 1.46%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 285/65R18 adds 0.55% 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 32.41″ 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 aliases305/60R18
- Diameter
- 32.41″ / 823.2mm
- Section Width
- 12.01″
- Sidewall
- 7.2″ / 183mm
- Circumference
- 101.82″
- Revs/Mile
- 622
285/60R18
- Diameter
- 31.46″ / 799.2mm
- Section Width
- 11.22″
- Sidewall
- 6.73″ / 171mm
- Circumference
- 98.85″
- Revs/Mile
- 641
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 58.25 mph (93.75 km/h). Your speedometer reads 2.92% high versus actual speed.