How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.61%

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

-1.61%

Absolute Difference

-0.5"

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
7068.9-1.1
8078.7-1.3
Tire 1Dia. 31.06 ″Rim 17 ″7.03 ″Width 10.04 ″Revs/Mile 649.4Circum. 97.6″Tire 2Dia. 30.56 ″Rim 17 ″6.78 ″Width 10.43 ″Revs/Mile 659.9Circum. 96.0″
Tire 1
Specification
Tire 2
31.06"
Diameter
30.56"
10.04"
Width
10.43"
7.03"
Sidewall
6.78"
97.563"
Circum.
96.016"
649.4
Revs/Mile
659.9

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