How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-0.72%

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

-0.72%

Absolute Difference

-0.18"

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
2019.9-0.1
3029.8-0.2
4039.7-0.3
5049.6-0.4
6059.6-0.4
7069.5-0.5
8079.4-0.6
Tire 1Dia. 25.16 ″Rim 15 ″5.08 ″Width 8.46 ″Revs/Mile 801.7Circum. 79.0″Tire 2Dia. 24.98 ″Rim 15 ″4.99 ″Width 7.68 ″Revs/Mile 807.4Circum. 78.5″
Tire 1
Specification
Tire 2
25.16"
Diameter
24.98"
8.46"
Width
7.68"
5.08"
Sidewall
4.99"
79.035"
Circum.
78.478"
801.7
Revs/Mile
807.4

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