205/65R16 vs 215/50R18
Comparison of overall diameter, sidewall, speedometer error, and ride-height change between these two tire sizes.
205/65R16
- Section width
- 205 mm
- Aspect ratio
- 65%
- Rim
- 16"
- Sidewall
- 133.3 mm
- Overall diameter
- 672.9 mm
- Revs / mile
- 761
215/50R18
- Section width
- 215 mm
- Aspect ratio
- 50%
- Rim
- 18"
- Sidewall
- 107.5 mm
- Overall diameter
- 672.2 mm
- Revs / mile
- 762
Difference
- Overall diameter
- -0.7 mm (-0.10%)
- Sidewall
- -25.8 mm
- Tread width
- +10 mm
- Ride height (axle)
- -0.3 mm
- Speedometer error
- -0.10%
- At indicated 60 mph
- actual 59.94 mph
Will 215/50R18 fit instead of 205/65R16?
The overall diameter changes by 0.10%. Most manufacturers consider a swap acceptable when the difference stays under 3% — beyond that, you may see speedometer error, ABS/TPMS warnings, or wheel-well clearance problems. This page only covers the math; your vehicle's wheel arches, suspension geometry, and load rating still matter.
What the numbers mean
- Overall diameter is the outside-to-outside height of the tire. Affects ride height, gearing, and speedometer.
- Sidewall is the height of the rubber from rim to tread. Lower sidewall = sharper steering, harsher ride.
- Speedometer error is the percentage your indicated speed will be off after the swap (positive = speedo reads lower than actual).