235/80R17 vs 245/80R17
Going from one to the other changes the overall height by +2.0 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/80R17 | 245/80R17 | Change |
|---|---|---|---|
| Overall height | 31.8" | 32.4" | +2.0 % |
| Sidewall | 7.40" | 7.72" | +4.3 % |
| Section width | 235 mm | 245 mm | +4.3 % |
| Circumference | 99.9" | 101.9" | +2.0 % |
| Revs per mile | 634 | 622 | -2.0 % |
| Axle height | 15.90" | 16.22" | +8.0 mm |
| Approved rim width | 6.5–8.5" | 7–9" | overlap 7–8.5" |
Both are approved on a rim 7" to 8.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 235/80R17. Fit 245/80R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 |
| 50 mph | 51.0 mph | +1.0 |
| 70 mph | 71.4 mph | +1.4 |
| 90 mph | 91.8 mph | +1.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 10,198 on the road, so it under-counts by 198. At a true 70 mph the first turns 740 times a minute, the second 725.
What drivers reported
235/80R17 carries 17 complaints. Nobody has filed one naming 245/80R17.