17-inch rim · tyre size comparison

225/45 R17 vs 225/55 R17

225/55 R17 is 45 mm (1.77 in) taller than 225/45 R17, a +7.09% difference in overall diameter. That is outside the ±3% limit commonly used to screen a tire size change, so expect a noticeable speedometer error; it is a nominal calculation, not a fitment approval.

Diameter difference
+45 mm
+1.77 in · +7.09%
Indicated 70 mph
75 mph
Actual speed on 225/55 R17, if the speedometer was accurate on 225/45 R17.
Sidewall height
+22.5 mm
101.25 mm to 123.75 mm.
Compare in the calculator225/45 R17 size guide225/55 R17 size guideSpeedometerWhat changes

Dimensions side by side

225/45 R17 and 225/55 R17 dimensions
Measurement225/45 R17225/55 R17Difference
Overall diameter634.3 mm24.97 in679.3 mm26.74 in+45 mm (+7.09%)+1.77 in
Section width225 mm8.86 in225 mm8.86 in0 mm0 in
Sidewall height101.25 mm3.99 in123.75 mm4.87 in+22.5 mm+0.89 in
Circumference1,992.71 mm78.45 in2,134.08 mm84.02 in+141.37 mm+5.57 in
Rim diameter431.8 mm17 in431.8 mm17 in0 mm0 in
Revolutions per mile807.61754.11-53.5
Revolutions per km501.83468.59-33.24
225/45 R17225/55 R17
Nominal diameters at the same scale. The inner circle is the rim.

Calculated from the nominal size codes, without load or tread wear. Real tyres vary by model, rim width and pressure, so the exact tyre's published dimensions take priority.

Speedometer with 225/55 R17

If the speedometer was accurate on 225/45 R17, fitting 225/55 R17 means the car is travelling 7.09% faster than it shows, and the odometer under-records distance by about the same amount.

Indicated speed versus calculated road speed on 225/55 R17
Speedometer showsActual on 225/55 R17Difference
30 mph32.13 mph+2.13 mph
50 mph53.55 mph+3.55 mph
60 mph64.26 mph+4.26 mph
70 mph74.97 mph+4.97 mph
50 km/h53.55 km/h+3.55 km/h
100 km/h107.09 km/h+7.09 km/h

UN ECE Regulation 39, used in the UK and EU, does not allow a speedometer to show less than the true speed, so many read slightly high from the factory. A taller tyre uses up some of that margin. Calibration varies by car; these figures are the tyre-size effect only.

What changes from 225/45 R17 to 225/55 R17

  • Wheels

    Both fit 17-inch wheels. Our rim-width starting estimate is 7 to 8 inches for 225/45 R17 and 6.5 to 7.5 inches for 225/55 R17, so a 7 to 7.5-inch wheel sits in both ranges. The exact tyre's approved rim range takes priority.

  • Sidewall and ride comfort

    225/55 R17 has 22.5 mm more sidewall (123.75 vs 101.25 mm). A taller sidewall usually rides noticeably softer and gives the rim more protection from potholes and kerbs, at the cost of some steering sharpness.

  • Contact width

    Both are 225 mm in nominal section width, so the tread is about as wide. Contact patch area is set mostly by load and pressure, so grip differences come more from the tyre model than this size change.

  • Wheel well clearance

    Ride height changes by about +22.5 mm, and the top of the tyre moves the same distance closer to the arch. On the same wheel, the sidewalls stay in roughly the same place side to side. Check clearance at full steering lock and full suspension compression, especially on a lowered car.

  • Gearing

    The effective final drive changes by -6.62%: 3,000 rpm at a given road speed becomes about 2,800 rpm. Gearing gets considerably longer, so cruising revs drop and acceleration in each gear softens.

  • ABS, stability control and AWD

    These systems compare wheel speeds. Fit the same size on both ends of an axle; with a 7.1% diameter gap, never mix 225/45 R17 and 225/55 R17 on an AWD car, and follow the car maker's rolling-circumference limits, which can be much tighter than 3%.

General tendencies from the nominal numbers, not a test of any tyre. Load index, speed rating, tyre construction and the car's approved sizes matter more than these rules of thumb.

Explained in our guides

Cars in our guides using these sizes

Factory trims and popular community setups from our fitment guides. A popular setup is not a factory approval; each guide explains its trims, axles and clearance limits.

225/45 R17

225/55 R17

More comparisons

225/45 R17 compared

205/50 R17 vs 225/45 R17225/45 R17 vs 245/40 R17215/45 R17 vs 225/45 R17225/45 R17 vs 235/45 R17225/45 R17 vs 235/40 R17225/45 R17 vs 225/50 R17

225/55 R17 compared

215/60 R17 vs 225/55 R17225/55 R17 vs 235/55 R17225/55 R17 vs 235/50 R17225/50 R17 vs 225/55 R17215/65 R17 vs 225/55 R17

Questions

Can I use 225/55 R17 instead of 225/45 R17?

Both fit 17-inch wheels. The diameter difference is +7.09%, outside the ±3% screening limit, so most fitters would treat it as a different size class rather than a direct replacement. That does not approve fitment: check the car maker's approved sizes, load index, speed rating, rim width and clearance first.

How much bigger is 225/55 R17 than 225/45 R17?

Overall diameter is 45 mm (1.77 in) larger: 679.3 vs 634.3 mm. Section width is the same, and the sidewall is 22.5 mm taller. These are nominal figures; real tyres vary by model and rim width.

Will 225/55 R17 change my speedometer reading?

Yes, by 7.09%. If the speedometer was accurate on 225/45 R17, an indicated 60 mph would be about 64.3 mph on 225/55 R17, and an indicated 100 km/h about 107.1 km/h. You would be going faster than the speedometer shows.

Which is better, 225/45 R17 or 225/55 R17?

Neither in general. 225/55 R17 has the taller sidewall, which usually rides more comfortably; 225/45 R17 usually steers more sharply. The size listed for your car's trim, on its placard or in the handbook, is the safe default.

Check the exact tyre

Size codes give nominal dimensions. Before buying, confirm the size is approved for your car and check the exact tyre's load and speed ratings and published dimensions.

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