How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.11%

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

1.11%

Absolute Difference

0.3"

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
2020.2+0.2
3030.3+0.3
4040.4+0.4
5050.6+0.6
6060.7+0.7
7070.8+0.8
8080.9+0.9
Tire 1Dia. 27.00 ″Rim 16 ″5.50 ″Width 8.46 ″Revs/Mile 746.9Circum. 84.8″Tire 2Dia. 27.30 ″Rim 16 ″5.65 ″Width 8.07 ″Revs/Mile 738.8Circum. 85.8″
Tire 1
Specification
Tire 2
27"
Diameter
27.3"
8.46"
Width
8.07"
5.5"
Sidewall
5.65"
84.835"
Circum.
85.763"
746.9
Revs/Mile
738.8

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