235/65R17 vs 245/65R17 — where the extra half inch of height comes from
A CR-V's single available step, and the mechanism that makes a wider tire a taller one.
245/65R17 is 0.51 in taller than 235/65R17 (1.76%) and 0.39 in wider. A speedometer calibrated for 235/65R17 would under-read by 1.76%.
Measured against each other
Overall diameter
29.03 in29.54 in+0.51 in (+1.76%)Section width
9.25 in / 235 mm9.65 in / 245 mm+0.39 in (+4.26%)Sidewall height
6.01 in6.27 in+0.26 inCircumference
91.2 in92.8 in+1.6 inRevolutions per mile
694.8682.8-12.0Ride height at the axle
——+0.26 inSpeedometer reading
——+1.76% under-read
| Dimension | 235/65R17 | 245/65R17 | Change |
|---|---|---|---|
| Overall diameter | 29.03 in | 29.54 in | +0.51 in (+1.76%) |
| Section width | 9.25 in / 235 mm | 9.65 in / 245 mm | +0.39 in (+4.26%) |
| Sidewall height | 6.01 in | 6.27 in | +0.26 in |
| Circumference | 91.2 in | 92.8 in | +1.6 in |
| Revolutions per mile | 694.8 | 682.8 | -12.0 |
| Ride height at the axle | — | — | +0.26 in |
| Speedometer reading | — | — | +1.76% under-read |
Calibrated for 235/65R17, running 245/65R17
- Dial reads 30
- 30.5 mph
- Dial reads 50
- 50.9 mph
- Dial reads 70
- 71.2 mph
- Odometer counts 100
- 101.8 mi covered
Change either size in the comparison tool, or see the full speed table in the speedometer error calculator.
The interesting thing about this pair is not how small the change is. It is that a change described entirely in terms of width produces most of its effect in height.
Follow the arithmetic through
The instruction in both codes is identical: make the sidewall 65% of the section width.
- 235 mm × 0.65 = 152.75 mm, which is 6.01 in
- 245 mm × 0.65 = 159.25 mm, which is 6.27 in
Ten millimetres of extra width bought 6.5 mm of extra sidewall without anyone asking for it. Double it, because the sidewall sits above and below the wheel, and 10 mm of width has produced 13 mm of diameter — 0.51 in.
So the tire is 0.39 in wider and 0.51 in taller. The height change is larger than the width change that caused it, which is counter-intuitive until you have watched the multiplication happen.
What it means on the road
Nothing, is the honest answer. The gap stays proportional at every speed and stays trivial at all of them — it never grows into anything, because 1.77% of a bigger number is still 1.77%. The figures are on this page because the mechanism is worth understanding, not because the outcome is.
Why a CR-V owner is looking
Because 245/65R17 sits at the boundary between crossover sizes and light-truck sizes, and it is offered in rugged and all-terrain patterns that 235/65R17 is largely not. Owners fitting one are usually choosing a category of tire, and inheriting the half inch as a side effect.
Keeping the existing wheels does not keep the geometry fixed, either. A casing stretched over a wheel wider than the rim it was specified against flattens slightly and measures over its nominal width; the reverse happens on a narrower one. Which of those applies depends on the width stamped on the wheel and on the width range printed on the tire's data sheet, and neither figure is part of a size code or of this site's data.
The circumference figures
1.6 in more ground per revolution, 91.2 in against 92.8 in. That is the physical quantity behind every derived number on this page, and it is what a wheel-speed sensor is indirectly measuring when it counts pulses.
If the aspect ratio moved too
It does not here, and that is what makes this pairing clean. Where both move at once — 225/60R17 against 245/65R17, for instance — the two effects compound and the result is nearly four times as large from changes that look comparable on paper.