How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.44%

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

-2.44%

Absolute Difference

-0.71"

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
2019.5-0.5
3029.3-0.7
4039-1
5048.8-1.2
6058.5-1.5
7068.3-1.7
8078-2
Tire 1Dia. 29.04 ″Rim 20 ″4.52 ″Width 10.04 ″Revs/Mile 694.6Circum. 91.2″Tire 2Dia. 28.33 ″Rim 20 ″4.16 ″Width 9.25 ″Revs/Mile 712.0Circum. 89.0″
Tire 1
Specification
Tire 2
29.04"
Diameter
28.33"
10.04"
Width
9.25"
4.52"
Sidewall
4.16"
91.218"
Circum.
88.991"
694.6
Revs/Mile
712

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