How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.29%

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

-1.29%

Absolute Difference

-0.33"

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
3029.6-0.4
4039.5-0.5
5049.4-0.6
6059.2-0.8
7069.1-0.9
8079-1
Tire 1Dia. 25.49 ″Rim 15 ″5.25 ″Width 8.07 ″Revs/Mile 791.2Circum. 80.1″Tire 2Dia. 25.16 ″Rim 15 ″5.08 ″Width 8.46 ″Revs/Mile 801.7Circum. 79.0″
Tire 1
Specification
Tire 2
25.49"
Diameter
25.16"
8.07"
Width
8.46"
5.25"
Sidewall
5.08"
80.086"
Circum.
79.035"
791.2
Revs/Mile
801.7

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