285/65R18 vs 305/65R17
305/65R17 is a safe swap for 285/65R18 by the usual ±3% rule: the diameter differs by +0.07%.
Speedometer and odometer
With 305/65R17 on a car calibrated for 285/65R18, the speedometer reads 60.0 mph when you're really doing 60, and the odometer under-counts by 0.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 45.0 mph |
| 60 mph | 60.0 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.1 mph |
Other sizes close to 285/65R18
- 285/65R18 vs 275/65R18-1.57%
- 285/65R18 vs 275/70R18+1.75%
- 285/65R18 vs 285/70R17+0.37%
- 285/65R18 vs 265/65R18-3.14%
- 285/65R18 vs 265/70R18+0.06%
- 285/65R18 vs 255/70R18-1.63%
- 285/65R18 vs 255/65R18-4.71%
- 285/65R18 vs 33x12.50R18+1.27%
- 285/65R18 vs 285/60R18-3.44%
- 285/65R18 vs 305/65R18+3.14%
- 285/65R18 vs 275/60R18-4.89%
- 285/65R18 vs 305/60R18-0.54%
Questions
Can I replace 285/65R18 with 305/65R17?
305/65R17 is a safe swap for 285/65R18 by the usual ±3% rule: the diameter differs by +0.07%.
What's the difference between 285/65R18 and 305/65R17?
305/65R17 is 0.02" taller and 20 mm wider; the sidewall is +0.51". At an indicated 60 mph you'd actually be doing 60.0 mph.
Will 305/65R17 fit on 285/65R18 wheels?
No — 285/65R18 needs a 18" wheel and 305/65R17 a 17" wheel. This is a plus/minus-size swap that changes wheels too.