How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.67%

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

-1.67%

Absolute Difference

-0.42"

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
3029.5-0.5
4039.3-0.7
5049.2-0.8
6059-1
7068.8-1.2
8078.7-1.3
Tire 1Dia. 25.16 ″Rim 15 ″5.08 ″Width 8.46 ″Revs/Mile 801.7Circum. 79.0″Tire 2Dia. 24.74 ″Rim 15 ″4.87 ″Width 8.86 ″Revs/Mile 815.1Circum. 77.7″
Tire 1
Specification
Tire 2
25.16"
Diameter
24.74"
8.46"
Width
8.86"
5.08"
Sidewall
4.87"
79.035"
Circum.
77.736"
801.7
Revs/Mile
815.1

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