305/65R17 vs 265/70R18
New overall diameter
32.61″
was 32.61″
True speed at an indicated 60
60.0 mph
no meaningful change
Revolutions per mile
619
was 618, +0
| Measurement | 305/65R17 | 265/70R18 | Change |
|---|---|---|---|
| Overall diameter | 32.61″ | 32.61″ | −0.00″ (−0.0%) |
| Sidewall height | 7.81″ (198.3 mm) | 7.30″ (185.5 mm) | −12.8 mm |
| Tread width | 305 mm | 265 mm | −40 mm |
| Circumference | 102.45″ | 102.44″ | −0.01″ |
| Revs per mile | 618 | 619 | +0 |
| Speedometer error | baseline | −0.0% | no change |
Diameter overlay
305/65R17 265/70R18
Speedometer check
With 265/70R18 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
25.0 mph actual
35 mph shown
35.0 mph actual
45 mph shown
45.0 mph actual
55 mph shown
55.0 mph actual
65 mph shown
65.0 mph actual
75 mph shown
75.0 mph actual
Common questions
- Will 265/70R18 fit instead of 305/65R17?
- Overall diameter changes 0.0%; section width changes -40 mm. Diameter comparison alone cannot confirm fitment. Verify the vehicle maker's approved rim width, tire load and speed ratings, and clearance at full steering lock and suspension compression. Confirm any possible ABS, traction-control, speedometer, and drivetrain effects with the vehicle maker or a qualified tire professional. Overall diameter goes from 32.61″ to 32.61″, a change of −0.0%. 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 265/70R18?
- At an indicated 60 mph you are really doing about 60.0 mph, a −0.0% error. That is effectively no change.
- What is the difference in revolutions per mile between 305/65R17 and 265/70R18?
- 305/65R17 turns about 618 times per mile and 265/70R18 turns about 619, a difference of +0. Your speedometer and odometer both count rotations, so this number is what throws them off.