ElpiAuto245/75R17 vs 265/70R17
265/70R17 is 0.4% taller (4 mm) than 245/75R17 — well inside the ±3% swap band.
Two sizes
Also accepts 35X12.50R17 and 31x10.5-15.
Both sizes, drawn to scale
1 grid = 1 inWhat each number means
The two size codes broken down — which digit is which, and what it does on the car.
Size A — 245/75R17
- 245section width9.6″ across the tread, sidewall to sidewall
- 75aspect ratiosidewall is 75% of the width — 7.2″ tall
- Rconstructionradial — standard on every modern road car
- 17wheel diametermounts on a 17-inch wheel
In flotation sizing: ≈ 31.5x9.6R17
Size B — 265/70R17
- 265section width10.4″ across the tread, sidewall to sidewall
- 70aspect ratiosidewall is 70% of the width — 7.3″ tall
- Rconstructionradial — standard on every modern road car
- 17wheel diametermounts on a 17-inch wheel
In flotation sizing: ≈ 31.6x10.4R17
245/75R17 vs 265/70R17, measurement by measurement
Every dimension in inches, with the difference and which size is bigger
| Measurement | 245/75R17 | 265/70R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 31.47″ | 31.61″ | +0.14″ | +0.4% |
| Section width | 9.65″ | 10.43″ | +0.79″ | +8.2% |
| Sidewall height | 7.23″ | 7.30″ | +0.07″ | +1.0% |
| Circumference | 98.86″ | 99.29″ | +0.43″ | +0.4% |
| Revs per mile | 640.9 | 638.1 | −2.8 | −0.4% |
| Revs per km | 398.2 | 396.5 | −1.7 | −0.4% |
| Approved rim width estimate | 7–9.5″ | 7.5–10″ | — | — |
Overall diameter is the controlling number — clearance, gearing, speedometer accuracy and odometer reading all follow from it. Revs per mile/km is what your ABS, speedometer and odometer actually count.
What changes on the road
Direction and rough size of each effect going from 245/75R17 to 265/70R17. Geometry only — real tires vary by brand and compound.
Speedometer & odometer error
What changes on the dash when the overall diameter changes.
A speedometer doesn't measure distance. It counts how fast the wheels turn and multiplies by a fixed factory number for tire circumference. Change the tire and that factory number is now wrong.
Going to a bigger tire, each turn covers more ground, so at a true 60.3 mph the wheels spin at the rate the factory calls 60. The dial reads low — you are speeding without knowing it. A smaller tire does the opposite, and the odometer also over-counts miles you didn't drive.
Over 10,000 indicated miles, this change means the odometer under-counts by roughly 44 miles.
| Speedometer reads | True speed on 265/70R17 | Error |
|---|---|---|
| 20 mph | 20.1 mph | +0.1 |
| 30 mph | 30.1 mph | +0.1 |
| 40 mph | 40.2 mph | +0.2 |
| 50 mph | 50.2 mph | +0.2 |
| 60 mph | 60.3 mph | +0.3 |
| 70 mph | 70.3 mph | +0.3 |
| 80 mph | 80.4 mph | +0.4 |
With 245/75R17 as the original size. A taller tire makes the dial read low — the gap grows with speed.
Reading this comparison
The overall diameter is what matters here: 265/70R17 is the taller tire. It sets ride height, gearing and how far the tire travels per revolution — which is what the speedometer and odometer count. Width and sidewall change fit and feel (a wider tire needs a wider wheel and more clearance; a shorter sidewall sharpens steering) but not the gearing.
Figures are geometric estimates from the size codes; real moulded tires vary by brand by 1–3%. Confirm load rating, wheel width and physical clearance on your vehicle before fitting. To compare any other two sizes, use the tire size comparison tool; to decode one size and see what else fits its wheel, the tire size calculator.