How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.56%

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

1.56%

Absolute Difference

0.46"

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
2020.3+0.3
3030.5+0.5
4040.6+0.6
5050.8+0.8
6060.9+0.9
7071.1+1.1
8081.2+1.2
Tire 1Dia. 29.57 ″Rim 18 ″5.79 ″Width 9.65 ″Revs/Mile 681.9Circum. 92.9″Tire 2Dia. 30.03 ″Rim 18 ″6.01 ″Width 9.25 ″Revs/Mile 671.7Circum. 94.3″
Tire 1
Specification
Tire 2
29.57"
Diameter
30.03"
9.65"
Width
9.25"
5.79"
Sidewall
6.01"
92.912"
Circum.
94.334"
681.9
Revs/Mile
671.7

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