205/55R16 vs 225/45R17
Switching from 205/55R16 to 225/45R17 changes the overall diameter by +2.4 mm (+0.4%) — inside the commonly used ±3% guideline. Every figure below is calculated from the two size codes with the standard formulas.
| Measurement | 205/55R16 | 225/45R17 | Difference |
|---|---|---|---|
| Overall diameter | 631.9 mm | 634.3 mm | +2.4 mm (+0.4%) |
| Overall diameter | 24.88 in | 24.97 in | +0.09 in |
| Tire width | 205 mm (8.07 in) | 225 mm (8.86 in) | +20 mm |
| Sidewall height | 112.8 mm (4.44 in) | 101.3 mm (3.99 in) | -11.5 mm |
| Wheel (rim) diameter | 16.0 in | 17.0 in | +1.0 in |
| Circumference | 1985 mm | 1993 mm | +8 mm |
| Revolutions per mile | 2547 | 2537 | -10 |
| Revolutions per km | 504 | 502 | -2 |
Speedometer error
Calibrated for 205/55R16, the speedometer under-reads or over-reads once 225/45R17 is fitted. This is your real speed at each indicated speed:
| Speedometer shows | Actual speed on 225/45R17 | Error |
|---|---|---|
| 20 mph | 20.1 mph | +0.1 mph |
| 40 mph | 40.2 mph | +0.2 mph |
| 60 mph | 60.2 mph | +0.2 mph |
| 80 mph | 80.3 mph | +0.3 mph |
| 100 mph | 100.4 mph | +0.4 mph |
How these two sizes are worked out
205/55R16 breaks down as a 205 mm tread width with a sidewall of 55% of that width (112.8 mm) on a 16.0-inch wheel, giving an overall diameter of 631.9 mm (24.88 in). 225/45R17 works out to 634.3 mm (24.97 in) the same way. The standard formulas are the same ones used on the tire size calculator page: diameter = rim × 25.4 + 2 × sidewall, circumference = π × diameter, revolutions per mile = 63,360 ÷ diameter in inches.
Nominal sizes vary slightly between brands and models, and tread wear shrinks a tire over its life. These figures follow the size codes exactly; your vehicle manual or a professional tire shop is the authority for what fits your vehicle.
More comparisons
Frequently asked questions
Can I replace 205/55R16 tires with 225/45R17?
The diameter change is +0.4%, which is within the commonly used ±3% guideline. Diameter is only one part of fitment — wheel width range, load index, speed rating and physical clearance all have to check out too, so confirm with your vehicle manual or a professional tire shop before buying.
Will 225/45R17 make my speedometer read wrong?
Yes, by the diameter ratio. When the dial shows 60 mph you are really doing 60.2 mph on 225/45R17. The full table above covers 20 to 100 mph.
Which tire is taller, 205/55R16 or 225/45R17?
225/45R17 is taller — 634.3 mm against 631.9 mm overall diameter, a difference of 2.4 mm.