How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

0.2%

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

0.2%

Absolute Difference

0.06"

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
20200
3030.1+0.1
4040.1+0.1
5050.1+0.1
6060.1+0.1
7070.1+0.1
8080.2+0.2
Tire 1Dia. 30.04 ″Rim 19 ″5.52 ″Width 10.04 ″Revs/Mile 671.3Circum. 94.4″Tire 2Dia. 30.10 ″Rim 19 ″5.55 ″Width 9.25 ″Revs/Mile 670.0Circum. 94.6″
Tire 1
Specification
Tire 2
30.04"
Diameter
30.1"
10.04"
Width
9.25"
5.52"
Sidewall
5.55"
94.384"
Circum.
94.569"
671.3
Revs/Mile
670

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