How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.07%

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

-1.07%

Absolute Difference

-0.3"

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
2019.8-0.2
3029.7-0.3
4039.6-0.4
5049.5-0.5
6059.4-0.6
7069.3-0.7
8079.1-0.9
Tire 1Dia. 28.04 ″Rim 18 ″5.02 ″Width 10.04 ″Revs/Mile 719.3Circum. 88.1″Tire 2Dia. 27.74 ″Rim 18 ″4.87 ″Width 10.83 ″Revs/Mile 726.9Circum. 87.2″
Tire 1
Specification
Tire 2
28.04"
Diameter
27.74"
10.04"
Width
10.83"
5.02"
Sidewall
4.87"
88.088"
Circum.
87.161"
719.3
Revs/Mile
726.9

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