How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-0.32%

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

-0.32%

Absolute Difference

-0.09"

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
2019.9-0.1
3029.9-0.1
4039.9-0.1
5049.8-0.2
6059.8-0.2
7069.8-0.2
8079.7-0.3
Tire 1Dia. 27.74 ″Rim 18 ″4.87 ″Width 8.86 ″Revs/Mile 726.9Circum. 87.2″Tire 2Dia. 27.65 ″Rim 18 ″4.82 ″Width 9.65 ″Revs/Mile 729.5Circum. 86.9″
Tire 1
Specification
Tire 2
27.74"
Diameter
27.65"
8.86"
Width
9.65"
4.87"
Sidewall
4.82"
87.161"
Circum.
86.851"
726.9
Revs/Mile
729.5

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