How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.43%

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

-1.43%

Absolute Difference

-0.39"

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
4039.4-0.6
5049.3-0.7
6059.1-0.9
7069-1
8078.9-1.1
Tire 1Dia. 27.25 ″Rim 18 ″4.63 ″Width 9.25 ″Revs/Mile 740.1Circum. 85.6″Tire 2Dia. 26.86 ″Rim 18 ″4.43 ″Width 8.86 ″Revs/Mile 750.9Circum. 84.4″
Tire 1
Specification
Tire 2
27.25"
Diameter
26.86"
9.25"
Width
8.86"
4.63"
Sidewall
4.43"
85.615"
Circum.
84.378"
740.1
Revs/Mile
750.9

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