How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.77%

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

-1.77%

Absolute Difference

-0.49"

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
2019.6-0.4
3029.5-0.5
4039.3-0.7
5049.1-0.9
6058.9-1.1
7068.8-1.2
8078.6-1.4
Tire 1Dia. 27.74 ″Rim 18 ″4.87 ″Width 8.86 ″Revs/Mile 726.9Circum. 87.2″Tire 2Dia. 27.25 ″Rim 18 ″4.63 ″Width 9.25 ″Revs/Mile 740.1Circum. 85.6″
Tire 1
Specification
Tire 2
27.74"
Diameter
27.25"
8.86"
Width
9.25"
4.87"
Sidewall
4.63"
87.161"
Circum.
85.615"
726.9
Revs/Mile
740.1

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