How it works

TireFlows

Get diameter, speedometer impact, and alternate sizes — free, no signup.

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.94%

Safety Rating

Safe

Within the recommended 3% safety margin.

The 3% rule is a common reference — not vehicle-specific advice. How it works

Speedometer Error

1.94%

Absolute Difference

0.61"

Speedometer

Assumes Tire 1 is what the speedometer is calibrated for. Shows approximate actual speed if you switch to Tire 2.

Reading (mph)Actual (mph)Difference
2020.4+0.4
3030.6+0.6
4040.8+0.8
5051+1
6061.2+1.2
7071.4+1.4
8081.6+1.6
Tire 1Dia. 31.46 ″Rim 18 ″6.73 ″Width 11.22 ″Revs/Mile 641.0Circum. 98.8″Tire 2Dia. 32.07 ″Rim 18 ″7.04 ″Width 10.83 ″Revs/Mile 628.8Circum. 100.8″
Tire 1
Specification
Tire 2
31.46"
Diameter
32.07"
11.22"
Width
10.83"
6.73"
Sidewall
7.04"
98.849"
Circum.
100.766"
641
Revs/Mile
628.8

How results are calculated

Tire dimensions are calculated from the metric size format (width / aspect ratio / rim diameter). Diameter, circumference, and revolutions per mile are derived mathematically — no fitment or vehicle data is used.

The 3% rule is a general reference for acceptable diameter difference, not a guarantee. Always check your vehicle manual or consult a tire professional.

How it works