CALCULATOR · FREE免费 · Free
Tire Size Comparison
Enter stock and new tire width, aspect ratio and rim diameter to compare overall diameter, speedometer error and radius change.
--Stock diameter · in
--New diameter · in
--Diameter change · %
--Speedometer error · %
--Radius change · in
Estimates only; verify on site before ordering or building.
Example
| Item | Value | Unit |
|---|---|---|
| Stock width | 225 | mm |
| Stock aspect | 45 | % |
| Stock rim | 17 | in |
| New width | 235 | mm |
| New aspect | 40 | % |
| New rim | 18 | in |
| Stock diameter | 24.97 | in |
| New diameter | 25.4 | in |
| Diameter change | 1.72 | % |
| Speedometer error | 1.72 | % |
| Radius change | 0.21 | in |
Where people go wrong
- Looking only at the larger rim and ignoring the overall diameter.
- Going past a 3 percent diameter change, which throws off the speedometer and odometer.
- Skipping a clearance check at full lock and full load.
FAQ
How much diameter change is safe?
Keep it within 3 percent; beyond that the speedometer error is noticeable and ABS or shift logic may be affected.
Does a taller tire make the speedometer read faster or slower?
Slower. Actual speed is higher than indicated, so watch your speed.