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.
For the effect on road speed and distance, see our worked speedometer example. When maintaining this set, use the rotation pattern guide to check whether tire direction or different front and rear sizes restrict rotation.
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%). These are nominal diameter comparisons, not approved replacements. Check vehicle-approved sizes, rim width, load and speed ratings, and clearance before changing size.