How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

0.59%

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

0.59%

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
2020.1+0.1
3030.2+0.2
4040.2+0.2
5050.3+0.3
6060.4+0.4
7070.4+0.4
8080.5+0.5
Tire 1Dia. 30.43 ″Rim 20 ″5.22 ″Width 10.43 ″Revs/Mile 662.7Circum. 95.6″Tire 2Dia. 30.61 ″Rim 20 ″5.31 ″Width 9.65 ″Revs/Mile 658.9Circum. 96.2″
Tire 1
Specification
Tire 2
30.43"
Diameter
30.61"
10.43"
Width
9.65"
5.22"
Sidewall
5.31"
95.608"
Circum.
96.165"
662.7
Revs/Mile
658.9

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