How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.97%

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

1.97%

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. 30.91 ″Rim 19 ″5.95 ″Width 10.83 ″Revs/Mile 652.5Circum. 97.1″Tire 2Dia. 31.52 ″Rim 19 ″6.26 ″Width 10.43 ″Revs/Mile 639.9Circum. 99.0″
Tire 1
Specification
Tire 2
30.91"
Diameter
31.52"
10.83"
Width
10.43"
5.95"
Sidewall
6.26"
97.105"
Circum.
99.022"
652.5
Revs/Mile
639.9

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