How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1%

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%

Absolute Difference

-0.25"

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
2019.8-0.2
3029.7-0.3
4039.6-0.4
5049.5-0.5
6059.4-0.6
7069.3-0.7
8079.2-0.8
Tire 1Dia. 24.97 ″Rim 17 ″3.99 ″Width 8.86 ″Revs/Mile 807.6Circum. 78.5″Tire 2Dia. 24.72 ″Rim 17 ″3.86 ″Width 9.65 ″Revs/Mile 816.0Circum. 77.6″
Tire 1
Specification
Tire 2
24.97"
Diameter
24.72"
8.86"
Width
9.65"
3.99"
Sidewall
3.86"
78.453"
Circum.
77.649"
807.6
Revs/Mile
816

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