305/65R18
305/65R18 is uncommon as OEM fitment but appears as an aftermarket upsize option. At 33.61″ diameter with a 7.81″ sidewall (65% of section width), this size turns 600 revolutions per mile.
About 305/65R18
305/65R18 is less common as a factory fitment but is available as an aftermarket size, so SKU selection is narrower than mainstream OEM sizes. At 33.61″ overall diameter, 305/65R18 turns 600 revolutions per mile, which is the reference point the factory speedometer and odometer were calibrated against. The 65% 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 295/65R18 drops diameter by 1.52%, which stays within the ±3% fitment safe zone for most vehicles. If you are shopping for a direct replacement, any tire within roughly ±0.7″ of the 33.61″ 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 aliases305/65R18
- Diameter
- 33.61″ / 853.7mm
- Section Width
- 12.01″
- Sidewall
- 7.81″ / 198.25mm
- Circumference
- 105.59″
- Revs/Mile
- 600
285/65R18
- Diameter
- 32.59″ / 827.7mm
- Section Width
- 11.22″
- Sidewall
- 7.29″ / 185.25mm
- Circumference
- 102.37″
- Revs/Mile
- 619
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 58.17 mph (93.62 km/h). Your speedometer reads 3.05% high versus actual speed.