How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.21%

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

2.21%

Absolute Difference

0.69"

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
3030.7+0.7
4040.9+0.9
5051.1+1.1
6061.3+1.3
7071.5+1.5
8081.8+1.8
Tire 1Dia. 31.22 ″Rim 20 ″5.61 ″Width 11.22 ″Revs/Mile 646.0Circum. 98.1″Tire 2Dia. 31.91 ″Rim 20 ″5.95 ″Width 10.83 ″Revs/Mile 632.0Circum. 100.2″
Tire 1
Specification
Tire 2
31.22"
Diameter
31.91"
11.22"
Width
10.83"
5.61"
Sidewall
5.95"
98.082"
Circum.
100.246"
646
Revs/Mile
632

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