How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

0.45%

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

0.45%

Absolute Difference

0.14"

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
2020.1+0.1
3030.1+0.1
4040.2+0.2
5050.2+0.2
6060.3+0.3
7070.3+0.3
8080.4+0.4
Tire 1Dia. 30.91 ″Rim 19 ″5.95 ″Width 10.83 ″Revs/Mile 652.5Circum. 97.1″Tire 2Dia. 31.05 ″Rim 19 ″6.02 ″Width 10.04 ″Revs/Mile 649.6Circum. 97.5″
Tire 1
Specification
Tire 2
30.91"
Diameter
31.05"
10.83"
Width
10.04"
5.95"
Sidewall
6.02"
97.105"
Circum.
97.538"
652.5
Revs/Mile
649.6

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