Comparison of tire sizes 155/70 R12 and 145/70 R13

155/70R12
155 Tire width
70 Profile height
R12 Tire diameter
610 RPM per km
155mm109mm522mm1639mm
155
70
12
145
70
13
Parameters Sizes Old New
Diameter, mm522533+11 (+2.1%)
Width, mm155145-10 (-6.5%)
Circumference, mm16391675+36 (+2.2%)
Profile height, mm109102-7 (-6.4%)
RPM per km610597-13 (-2.1%)
Clearance change, mm+6
Result:
The diameter differs by 2.1%.
Speedometer reading (km/h)
Real speed (km/h)102.2
Difference (km/h)2.2

Sizes for comparison of tires 155/70 R12

R12
R13 +1
R14 +2

Sizes for comparison of tires 145/70 R13

R13
R12 -1
R14 +1