How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.58%

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

1.58%

Absolute Difference

0.43"

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
3030.5+0.5
4040.6+0.6
5050.8+0.8
6060.9+0.9
7071.1+1.1
8081.3+1.3
Tire 1Dia. 27.18 ″Rim 17 ″5.09 ″Width 9.25 ″Revs/Mile 742.1Circum. 85.4″Tire 2Dia. 27.61 ″Rim 17 ″5.31 ″Width 9.65 ″Revs/Mile 730.5Circum. 86.7″
Tire 1
Specification
Tire 2
27.18"
Diameter
27.61"
9.25"
Width
9.65"
5.09"
Sidewall
5.31"
85.38"
Circum.
86.74"
742.1
Revs/Mile
730.5

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