How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.67%

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

1.67%

Absolute Difference

0.51"

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
2020.3+0.3
3030.5+0.5
4040.7+0.7
5050.8+0.8
6061+1
7071.2+1.2
8081.3+1.3
Tire 1Dia. 30.56 ″Rim 17 ″6.78 ″Width 10.43 ″Revs/Mile 659.9Circum. 96.0″Tire 2Dia. 31.07 ″Rim 17 ″7.04 ″Width 10.83 ″Revs/Mile 649.0Circum. 97.6″
Tire 1
Specification
Tire 2
30.56"
Diameter
31.07"
10.43"
Width
10.83"
6.78"
Sidewall
7.04"
96.016"
Circum.
97.624"
659.9
Revs/Mile
649

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