How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.45%

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

-2.45%

Absolute Difference

-0.63"

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
2019.5-0.5
3029.3-0.7
4039-1
5048.8-1.2
6058.5-1.5
7068.3-1.7
8078-2
Tire 1Dia. 25.72 ″Rim 18 ″3.86 ″Width 9.65 ″Revs/Mile 784.2Circum. 80.8″Tire 2Dia. 25.09 ″Rim 18 ″3.54 ″Width 8.86 ″Revs/Mile 803.9Circum. 78.8″
Tire 1
Specification
Tire 2
25.72"
Diameter
25.09"
9.65"
Width
8.86"
3.86"
Sidewall
3.54"
80.791"
Circum.
78.812"
784.2
Revs/Mile
803.9

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