GarageCalc What 235/85R16 means
235 is the section width in millimeters (9.3 in). 85 is the aspect ratio: the sidewall is 85 percent of the width, so 235 × 0.85 = 200 mm (7.9 in). R is radial construction, and 16 is the wheel diameter in inches (406 mm). Stack two sidewalls on the wheel and you get the overall diameter: 406 + 2 × 200 = 806 mm, or 31.7 in.
A full marking adds a load index and speed rating after the size, for example 235/85R16 91V. Those two codes set how much weight and speed the tire is certified for; look them up in the load index chart and the speed rating chart.
Plus and minus sizing from 235/85R16
Similar diameter does not establish interchangeability. Follow the vehicle manufacturer's approved sizes; see Michelin's tire-size guidance.
Going up one wheel size, the closest match is 235/80R17 at +0.2% diameter with a 188 mm sidewall instead of 200 mm. No common 15-inch size stays within 3 percent either. The 3 percent cutoff is a comparison filter, not a fitment approval. Use vehicle-approved sizes and check rim width, load and speed ratings, and clearances. The comparison calculator shows the full speedometer table for any pair.
Frequently asked questions
How tall is a 235/85R16 tire?
31.7 inches (806 mm) in overall diameter: the 16-inch wheel (406 mm) plus two 200 mm sidewalls. Actual dimensions depend on the tire model, tread depth, pressure and load; check the tire manufacturer specifications.
What is 235/85R16 in inches?
31.7 x 9.3 R16: 31.7 inches tall, 9.3 inches wide, on a 16-inch wheel. The sidewall is 7.9 inches and the circumference is 99.7 inches, so the tire turns 636 times per mile.
What tire sizes are equivalent to 235/85R16?
Within 3 percent of the same diameter; on a 17-inch wheel: 235/80R17 (+0.2%), 245/75R17 (-0.8%). The percentage is the diameter change, which is also your speedometer error.