How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

0.08%

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

0.08%

Absolute Difference

0.02"

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
20200
30300
40400
50500
60600
7070.1+0.1
8080.1+0.1
Tire 1Dia. 25.16 ″Rim 15 ″5.08 ″Width 8.46 ″Revs/Mile 801.7Circum. 79.0″Tire 2Dia. 25.18 ″Rim 15 ″5.09 ″Width 9.25 ″Revs/Mile 801.0Circum. 79.1″
Tire 1
Specification
Tire 2
25.16"
Diameter
25.18"
8.46"
Width
9.25"
5.08"
Sidewall
5.09"
79.035"
Circum.
79.096"
801.7
Revs/Mile
801

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