How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.47%

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

1.47%

Absolute Difference

0.4"

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
2020.3+0.3
3030.4+0.4
4040.6+0.6
5050.7+0.7
6060.9+0.9
7071+1
8081.2+1.2
Tire 1Dia. 27.25 ″Rim 18 ″4.63 ″Width 9.25 ″Revs/Mile 740.1Circum. 85.6″Tire 2Dia. 27.65 ″Rim 18 ″4.82 ″Width 9.65 ″Revs/Mile 729.5Circum. 86.9″
Tire 1
Specification
Tire 2
27.25"
Diameter
27.65"
9.25"
Width
9.65"
4.63"
Sidewall
4.82"
85.615"
Circum.
86.851"
740.1
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