235/45R18 vs 265/60R18
New overall diameter
30.52″
was 26.33″
True speed at an indicated 60
69.6 mph
your speedo reads low
Revolutions per mile
661
was 766, −105
| Measurement | 235/45R18 | 265/60R18 | Change |
|---|---|---|---|
| Overall diameter | 26.33″ | 30.52″ | +4.19″ (+15.9%) |
| Sidewall height | 4.16″ (105.8 mm) | 6.26″ (159.0 mm) | +53.3 mm |
| Tread width | 235 mm | 265 mm | +30 mm |
| Circumference | 82.71″ | 95.88″ | +13.17″ |
| Revs per mile | 766 | 661 | −105 |
| Speedometer error | baseline | +15.9% | reads low |
Diameter overlay
235/45R18 265/60R18
Speedometer check
With 265/60R18 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
29.0 mph actual
35 mph shown
40.6 mph actual
45 mph shown
52.2 mph actual
55 mph shown
63.8 mph actual
65 mph shown
75.4 mph actual
75 mph shown
86.9 mph actual
Common questions
- Will 265/60R18 fit instead of 235/45R18?
- 15.9% is past the 5% mark, which is where this stops being a tire choice and starts being a project. Expect rubbing, meaningful speedometer error, and extra load on ABS, stability control and the drivetrain. Recalibration is the usual fix. Your speedometer will read low, so you are going faster than it says. Overall diameter goes from 26.33″ to 30.52″, a change of +15.9%. The rule of thumb most shops use: under 3% is fine, 3 to 5% needs a clearance check, over 5% needs recalibration.
- How far off will my speedometer read on 265/60R18?
- At an indicated 60 mph you are really doing about 69.6 mph, a +15.9% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 235/45R18 and 265/60R18?
- 235/45R18 turns about 766 times per mile and 265/60R18 turns about 661, a difference of −105. Your speedometer and odometer both count rotations, so this number is what throws them off.