275/40R22 vs 275/50R21
New overall diameter
31.83″
was 30.66″
True speed at an indicated 60
62.3 mph
your speedo reads low
Revolutions per mile
634
was 658, −24
| Measurement | 275/40R22 | 275/50R21 | Change |
|---|---|---|---|
| Overall diameter | 30.66″ | 31.83″ | +1.17″ (+3.8%) |
| Sidewall height | 4.33″ (110.0 mm) | 5.41″ (137.5 mm) | +27.5 mm |
| Tread width | 275 mm | 275 mm | +0 mm |
| Circumference | 96.33″ | 99.99″ | +3.66″ |
| Revs per mile | 658 | 634 | −24 |
| Speedometer error | baseline | +3.8% | reads low |
Diameter overlay
275/40R22 275/50R21
Speedometer check
With 275/50R21 fitted, when the speedometer shows the indicated speed, your actual speed is:
25 mph shown
26.0 mph actual
35 mph shown
36.3 mph actual
45 mph shown
46.7 mph actual
55 mph shown
57.1 mph actual
65 mph shown
67.5 mph actual
75 mph shown
77.9 mph actual
Common questions
- Will 275/50R21 fit instead of 275/40R22?
- Overall diameter changes 3.8%; section width changes 0 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 30.66″ to 31.83″, a change of +3.8%. 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 275/50R21?
- At an indicated 60 mph you are really doing about 62.3 mph, a +3.8% error. The speedometer reads low, so you are going faster than it shows.
- What is the difference in revolutions per mile between 275/40R22 and 275/50R21?
- 275/40R22 turns about 658 times per mile and 275/50R21 turns about 634, a difference of −24. Your speedometer and odometer both count rotations, so this number is what throws them off.