How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.82%

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

-2.82%

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
2019.4-0.6
3029.2-0.8
4038.9-1.1
5048.6-1.4
6058.3-1.7
7068-2
8077.7-2.3
Tire 1Dia. 29.40 ″Rim 17 ″6.20 ″Width 8.86 ″Revs/Mile 686.0Circum. 92.4″Tire 2Dia. 28.57 ″Rim 17 ″5.79 ″Width 9.65 ″Revs/Mile 705.8Circum. 89.8″
Tire 1
Specification
Tire 2
29.4"
Diameter
28.57"
8.86"
Width
9.65"
6.2"
Sidewall
5.79"
92.368"
Circum.
89.77"
686
Revs/Mile
705.8

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