How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.44%

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

-1.44%

Absolute Difference

-0.44"

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
4039.4-0.6
5049.3-0.7
6059.1-0.9
7069-1
8078.8-1.2
Tire 1Dia. 30.48 ″Rim 19 ″5.74 ″Width 10.43 ″Revs/Mile 661.8Circum. 95.7″Tire 2Dia. 30.04 ″Rim 19 ″5.52 ″Width 10.04 ″Revs/Mile 671.3Circum. 94.4″
Tire 1
Specification
Tire 2
30.48"
Diameter
30.04"
10.43"
Width
10.04"
5.74"
Sidewall
5.52"
95.744"
Circum.
94.384"
661.8
Revs/Mile
671.3

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