Diameter tolerance
A tire diameter change within about 3% is commonly treated as a practical limit, but always verify fitment for your vehicle.
D3 Orient — car calculators and fitment tools
Compare tire sizes, wheel offset, bolt patterns, center bore and fuel costs. Useful for choosing wheels, tires and checking compatibility before buying.
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Tire & Rim Calculator
Compare original and new tire sizes, rim width and offset. The result shows diameter, clearance, speedometer error and wheel position changes.
Original Size
195 / 65 R15
6J ET45
New Size
205 / 55 R16
7J ET45
Visual tire and wheel comparison
Compare overall diameter and wheel position. The drawing is scaled to the selected values.
Inner edge change
12.7 mm closer to suspension
Outer edge change
12.7 mm further outward
Original
New
Diameter and wheel position changes are small reference values.
The diagram is a comparison, not a fitment guarantee. Brake, suspension and fender clearance must be checked on the vehicle.
Results
Diameter change is within the 3% reference limit.
Clearance change
-1.3 mm
Speedometer error
-0.4 %
Actual at 100
99.6 km/h
| Parameter | Original | New | Difference |
|---|---|---|---|
| Total Diameter | 634.5 mm | 631.9 mm | -2.6 mm |
| Section Width | 195 mm | 205 mm | +10.0 mm |
| Sidewall Height | 126.8 mm | 112.8 mm | -14.0 mm |
| Circumference | 1993 mm | 1985 mm | -8 mm |
| Rim Width | 6.0" | 7.0" | +25.4 mm |
| Rim Offset | ET 45 | ET 45 | 0.0 mm |
| Strut Clearance | - | 12.7 mm closer to suspension | |
| Fender Poke | - | 12.7 mm pokes out further |
How to read tire markings
Example on tire sidewall
205/55 R16 91V XL DOT 2423
The main size is only part of the tire label. Load index, speed rating, reinforced construction and production date also matter when choosing tires.
| Marking | Meaning | Example |
|---|---|---|
| 205 | Tire section width in millimeters. | 205 mm |
| 55 | Sidewall height as a percentage of the width. | 55% of 205 mm |
| R | Radial tire construction. | R = radial |
| 16 | Rim diameter in inches. | 16 inch wheel |
| 91 | Load index. It must meet or exceed the vehicle requirement. | 91 = up to 615 kg per tire |
| V | Speed rating. It must be suitable for the car and local rules. | V = up to 240 km/h |
| XL | Reinforced tire with higher load capacity at the correct pressure. | XL / Extra Load |
| DOT 2423 | Production date: week and year. Here it means week 24 of 2023. | 24 / 2023 |
| M+S / 3PMSF | Season and winter performance markings. 3PMSF is the snowflake mountain symbol. | All-season or winter tire |
| Outside / Rotation | Mounting direction or outside sidewall marking for asymmetric or directional tires. | Install as marked |
Load and speed index quick reference
Common passenger-car examples. Use tires with load and speed ratings equal to or higher than the vehicle manufacturer requires.
Load index
| Index | Load per tire |
|---|---|
| 82 | 475 kg |
| 84 | 500 kg |
| 86 | 530 kg |
| 88 | 560 kg |
| 91 | 615 kg |
| 94 | 670 kg |
| 95 | 690 kg |
| 98 | 750 kg |
| 100 | 800 kg |
| 102 | 850 kg |
| 104 | 900 kg |
| 106 | 950 kg |
| 109 | 1030 kg |
Speed rating
| Code | Max speed |
|---|---|
| Q | 160 km/h |
| R | 170 km/h |
| S | 180 km/h |
| T | 190 km/h |
| H | 210 km/h |
| V | 240 km/h |
| W | 270 km/h |
| Y | 300 km/h |
| (Y) | > 300 km/h |
This is a quick reference only. Always follow the load and speed rating listed in the vehicle manual, door sticker or official tire approval.
Offset and clearance
Rim width and ET affect how close the wheel sits to the suspension and how far it moves toward the fender.
Speedometer
A smaller tire makes the actual road speed lower than the displayed speed. A larger tire does the opposite.
Always verify wheel fitment with your vehicle manual or a professional before buying. Brake clearance, suspension modifications and local regulations may affect compatibility.