How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-0.18%

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

-0.18%

Absolute Difference

-0.05"

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
20200
3029.9-0.1
4039.9-0.1
5049.9-0.1
6059.9-0.1
7069.9-0.1
8079.9-0.1
Tire 1Dia. 27.74 ″Rim 18 ″4.87 ″Width 8.86 ″Revs/Mile 726.9Circum. 87.2″Tire 2Dia. 27.69 ″Rim 18 ″4.84 ″Width 8.07 ″Revs/Mile 728.5Circum. 87.0″
Tire 1
Specification
Tire 2
27.74"
Diameter
27.69"
8.86"
Width
8.07"
4.87"
Sidewall
4.84"
87.161"
Circum.
86.975"
726.9
Revs/Mile
728.5

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