How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.55%

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

-1.55%

Absolute Difference

-0.49"

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
2019.7-0.3
3029.5-0.5
4039.4-0.6
5049.2-0.8
6059.1-0.9
7068.9-1.1
8078.8-1.2
Tire 1Dia. 31.65 ″Rim 16 ″7.82 ″Width 10.43 ″Revs/Mile 637.2Circum. 99.4″Tire 2Dia. 31.16 ″Rim 16 ″7.58 ″Width 10.83 ″Revs/Mile 647.3Circum. 97.9″
Tire 1
Specification
Tire 2
31.65"
Diameter
31.16"
10.43"
Width
10.83"
7.82"
Sidewall
7.58"
99.43"
Circum.
97.884"
637.2
Revs/Mile
647.3

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