How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.57%

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

-2.57%

Absolute Difference

-0.73"

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
3029.2-0.8
4039-1
5048.7-1.3
6058.5-1.5
7068.2-1.8
8077.9-2.1
Tire 1Dia. 28.39 ″Rim 19 ″4.69 ″Width 10.43 ″Revs/Mile 710.4Circum. 89.2″Tire 2Dia. 27.66 ″Rim 19 ″4.33 ″Width 10.83 ″Revs/Mile 729.1Circum. 86.9″
Tire 1
Specification
Tire 2
28.39"
Diameter
27.66"
10.43"
Width
10.83"
4.69"
Sidewall
4.33"
89.189"
Circum.
86.901"
710.4
Revs/Mile
729.1

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