275/55R20 vs 275/35R20
New overall diameter
27.58″
was 31.91″
True speed at an indicated 60
51.9 mph
speedometer reads high
Revolutions per mile
731
was 632 · +99
Switching from 275/55R20 to 275/35R20? Everything that changes is below — sidewall, tread width, circumference, revolutions per mile and speedometer error at road speeds.
| Measurement | 275/55R20 | 275/35R20 | Change |
|---|---|---|---|
| Overall diameter | 31.91″ | 27.58″ | −4.33″ (−13.6%) |
| Sidewall height | 5.95″ (151.3 mm) | 3.79″ (96.3 mm) | −55.0 mm |
| Tread width | 275 mm | 275 mm | +0 mm |
| Circumference | 100.25″ | 86.64″ | −13.61″ |
| Revs per mile | 632 | 731 | +99 |
| Speedometer error | baseline | −13.6% | reads high |
Diameter overlay
275/55R20 275/35R20
Speedometer check
With 275/35R20 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
21.6 mph actual
35 mph shown
30.2 mph actual
45 mph shown
38.9 mph actual
55 mph shown
47.5 mph actual
65 mph shown
56.2 mph actual
75 mph shown
64.8 mph actual
Common questions
- Will 275/35R20 fit instead of 275/55R20?
- Not recommended. A 13.6% diameter change exceeds the 5% rule. Expect significant speedometer error, potential clearance and rubbing issues, and stress on ABS, stability control and drivetrain components. Your speedometer will read higher than your true speed. Overall diameter goes from 31.91″ to 27.58″, a change of −13.6%. As a rule of thumb, under 3% is safe, 3–5% needs a clearance check, and over 5% is not recommended.
- How far off will my speedometer read on 275/35R20?
- At an indicated 60 mph you would actually be travelling about 51.9 mph — a −13.6% error. The speedometer reads high, so you are going slower than it shows.
- What is the difference in revolutions per mile between 275/55R20 and 275/35R20?
- 275/55R20 turns roughly 632 revolutions per mile; 275/35R20 turns roughly 731. That is a change of +99 revolutions per mile, which is what shifts odometer and speedometer readings.