How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.32%

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

-1.32%

Absolute Difference

-0.37"

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
2019.7-0.3
3029.6-0.4
4039.5-0.5
5049.3-0.7
6059.2-0.8
7069.1-0.9
8078.9-1.1
Tire 1Dia. 28.00 ″Rim 17 ″5.50 ″Width 8.46 ″Revs/Mile 720.2Circum. 88.0″Tire 2Dia. 27.63 ″Rim 17 ″5.31 ″Width 8.86 ″Revs/Mile 729.9Circum. 86.8″
Tire 1
Specification
Tire 2
28"
Diameter
27.63"
8.46"
Width
8.86"
5.5"
Sidewall
5.31"
87.977"
Circum.
86.802"
720.2
Revs/Mile
729.9

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