Does the calculator account for wheel width and offset?

No. It calculates nominal tyre geometry; wheel width, offset, centre bore, fixings and arch clearance are not assessed.

Why can actual tyre diameter differ from the calculation?

The formula uses nominal markings. Brand, model, wheel width, pressure, load and tread wear alter the real dimensions.

Confronto misure pneumatici

Inserisci due misure

Misura attualeMisura di riferimento

Misure pneumatico

Larghezza Spalla Cerchio

Nuova misuraMisura considerata

Misure pneumatico

Larghezza Spalla Cerchio

205/55 R16 means a 205 mm width, 55% aspect ratio and 16-inch rim.

Differenza minima

205/55 R16 → 225/45 R17

Variazione diametro+0,38 %

Confronto visivo

205/55 R16Attuale

225/45 R17Nuova

Variazioni principali

Altezza da terra+1,2 mmthe vehicle would theoretically rise

Velocità effettiva100,4 km/hwhen the speedometer shows 100 km/h

Distanza effettiva100,4 kmwhen the odometer records 100 km

Verifica un’altra velocità indicata

km/h

Confronto dettagliato delle misure

Nominal theoretical dimensions calculated from the tyre marking.

Dato	205/55 R16	225/45 R17	Differenza
Larghezza pneumatico
Altezza spalla
Diametro cerchio
Diametro esterno
Circonferenza teorica
Giri per chilometro

Scarto tachimetro

Theoretical road speed if the vehicle was calibrated for the first tyre size.

Tachimetro	Velocità effettiva teorica	Differenza

Important: this calculation isolates the effect of nominal tyre size. Factory calibration, pressure, load, tread wear and actual model dimensions also affect the reading.

Strumento aggiuntivo

Misure pneumatici equivalenti

Using 205/55 R16 find the closest nominal-diameter options for your chosen rim.

Mathematically close diameter options for rim R17. This does not confirm availability or suitability for a particular vehicle and wheel.

Misura pneumatico	Differenza diametro	Altezza da terra	Speed at 100 km/h	Azione

Come confrontare le misure degli pneumatici?

From the sidewall marking to clear diameter and speedometer changes

Find your current size

Check the tyre sidewall or vehicle placard and enter a size such as 205/55 R16.

Enter the new size

Select the size you are considering; the standard 225/45 R17 format is used.

Compare the changes

Review sidewall height, diameter, circumference, clearance, revolutions and theoretical speedometer readings.

Check the vehicle documents

A mathematically close size is not automatically suitable. Always use sizes approved by the vehicle manufacturer.

Cosa significa 205/55 R16?

Three main numbers describe the nominal tyre dimensions

205/55R16

205 – width

Nominal section width in millimetres.

55 – aspect ratio

The sidewall height is 55% of the width: 112.75 mm here.

R16 – construction and rim

R means radial construction and 16 is the rim diameter in inches.

Confronto 205/55 R16 e 225/45 R17

Domande frequenti sulle misure pneumatici

Answers about sidewall height, changing R16 to R17, speedometer difference and equivalent sizes

How do you calculate tyre sidewall height?

What is the difference between 205/55 R16 and 225/45 R17?

Which tyres can replace 205/55 R16?

Can R16 tyres be changed to R17?

How does tyre size affect the speedometer?

What tyre-diameter difference is acceptable?

How does ground clearance change?

Does the tool check wheel width and offset?

Why can actual tyre size differ from the result?

Does the calculator save entered sizes?