235/65R17 tyre size
737.3 mm diameter
29.03 in · 152.8 mm sidewall · 2.32 m rolling circumference · 432 rev/km
Reading 235/65R17
| 235 | Tread width in millimetres |
| 65 | Aspect ratio — sidewall height as a percentage of the width, so 235 × 65% = 152.8 mm |
| R | Radial construction, which is almost every road tyre made since the 1970s |
| 17 | Rim diameter in inches — 431.8 mm |
The aspect ratio is the part that catches people: it is a percentage of the width, not a fixed height. Widen the tread and keep the same aspect number and the tyre also gets taller. That is why 235/65R17 and a size with a smaller aspect number on a larger rim can be the same overall diameter.
The numbers
| Tread width | 235 mm · 9.25 in |
| Sidewall height | 152.8 mm · 6.01 in |
| Rim diameter | 17 in · 431.8 mm |
| Overall diameter | 737.3 mm · 29.03 in |
| Rolling circumference | 2316.3 mm · 2.32 m |
| Revolutions per kilometre | 432 |
| Revolutions per mile | 695 |
Sizes that fit in place of 235/65R17
A replacement is judged on rolling diameter, because that is what the speedometer, the ABS and the gearing all depend on. Anything within about 1% is treated as interchangeable; beyond 3% the speedometer error stops being ignorable.
| Size | Diameter | Difference | Speedometer at an indicated 100 |
|---|---|---|---|
| 255/55R18 | 737.7 mm | +0.05% | 100.1 km/h actual |
| 235/60R18 | 739.2 mm | +0.26% | 100.3 km/h actual |
| 295/35R21 | 739.9 mm | +0.35% | 100.4 km/h actual |
| 315/35R20 | 728.5 mm | -1.19% | 98.8 km/h actual |
| 275/40R20 | 728.0 mm | -1.26% | 98.7 km/h actual |
| 245/70R16 | 749.4 mm | +1.64% | 101.6 km/h actual |
| 225/65R17 | 724.3 mm | -1.76% | 98.2 km/h actual |
| 275/45R20 | 755.5 mm | +2.47% | 102.5 km/h actual |
Diameter is only half the question — the replacement also has to suit the rim width and the vehicle's load and speed ratings. Check the placard in the door frame before buying.
Other 17-inch sizes
| Size | Sidewall | Diameter |
|---|---|---|
| 205/50R17 | 102.5 mm | 636.8 mm |
| 215/45R17 | 96.8 mm | 625.3 mm |
| 215/55R17 | 118.3 mm | 668.3 mm |
| 215/60R17 | 129.0 mm | 689.8 mm |
| 225/45R17 | 101.3 mm | 634.3 mm |
| 225/50R17 | 112.5 mm | 656.8 mm |
| 225/55R17 | 123.8 mm | 679.3 mm |
| 225/60R17 | 135.0 mm | 701.8 mm |
Frequently asked questions
What does 235/65R17 mean?
235 is the tread width in millimetres, 65 is the sidewall height as a percentage of that width — so 235 × 65% = 152.8 mm of sidewall — and R17 is a radial tyre on a 17-inch rim. Overall diameter is 17 × 25.4 + 2 × 152.8 = 737.3 mm.
What is the overall diameter of a 235/65R17?
737.3 mm (29.03 inches), with a rolling circumference of 2.32 m — about 432 revolutions per kilometre.
What size is equivalent to a 235/65R17?
255/55R18 (+0.05%), 235/60R18 (+0.26%), 295/35R21 (+0.35%) — all within 1% of this diameter, which is the band inside which a manufacturer will list alternatives for the same car. Width and rim differ; rolling diameter does not.
How much does changing tyre size affect the speedometer?
A speedometer counts wheel revolutions, so it reads in proportion to the rolling diameter it was calibrated for. Fitting a tyre 1% larger makes the speedometer read 1% low — at an indicated 100 km/h you are doing 101. Most jurisdictions expect a speedometer to never under-read, which is why replacements are kept within about 3% and why the factory tyre usually reads a little high to begin with.