Worked example: 205/55R16 → 225/45R17 → 225/40R18
| Size | Wheel | Width | Sidewall | Height | Change vs 205/55R16 |
|---|---|---|---|---|---|
| 205/55R16 (stock) | 16 | 205 mm | 4.44 in | 24.88 in | — |
| 225/45R17 (+1) | 17 | 225 mm | 3.99 in | 24.97 in | +0.38% |
| 225/40R18 (+2) | 18 | 225 mm | 3.54 in | 25.09 in | +0.84% |
Each step adds an inch to the wheel and removes about an inch of height from the two sidewalls together. Width usually grows a little, which is why the wheel needs to be the right width for the new tire. The ±3% height guideline is quoted by Discount Tire’s tire size calculator and 1010tires; it is a rule of thumb.
Other calculated plus sizes for 205/55R16
| Size | Wheel | Height | Change | Width change |
|---|---|---|---|---|
| 175/50R18 | 18 in | 24.89 in | +0.05% | -30 mm |
| 195/45R18 | 18 in | 24.91 in | +0.13% | -10 mm |
| 225/45R17 | 17 in | 24.97 in | +0.38% | +20 mm |
| 215/40R18 | 18 in | 24.77 in | -0.43% | +10 mm |
| 185/55R17 | 17 in | 25.01 in | +0.54% | -20 mm |
| 205/50R17 | 17 in | 25.07 in | +0.78% | +0 mm |
| 195/50R17 | 17 in | 24.68 in | -0.81% | -10 mm |
| 225/40R18 | 18 in | 25.09 in | +0.84% | +20 mm |
| 215/45R17 | 17 in | 24.62 in | -1.04% | +10 mm |
| 175/55R17 | 17 in | 24.58 in | -1.20% | -30 mm |
What changes
- Sidewall shrinks: sharper steering response, less cushion, more wheel exposed.
- Wheel and tire cost more in most sizes.
- Load index and speed rating must still meet your vehicle’s needs.
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.
Going the other way for winter? See winter tire sizing.