How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.91%

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

2.91%

Absolute Difference

0.83"

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
2020.6+0.6
3030.9+0.9
4041.2+1.2
5051.5+1.5
6061.7+1.7
7072+2
8082.3+2.3
Tire 1Dia. 28.57 ″Rim 17 ″5.79 ″Width 9.65 ″Revs/Mile 705.8Circum. 89.8″Tire 2Dia. 29.40 ″Rim 17 ″6.20 ″Width 8.86 ″Revs/Mile 686.0Circum. 92.4″
Tire 1
Specification
Tire 2
28.57"
Diameter
29.4"
9.65"
Width
8.86"
5.79"
Sidewall
6.2"
89.77"
Circum.
92.368"
705.8
Revs/Mile
686

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