How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.68%

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

1.68%

Absolute Difference

0.45"

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
4040.7+0.7
5050.8+0.8
6061+1
7071.2+1.2
8081.3+1.3
Tire 1Dia. 26.86 ″Rim 18 ″4.43 ″Width 8.86 ″Revs/Mile 750.9Circum. 84.4″Tire 2Dia. 27.31 ″Rim 18 ″4.66 ″Width 8.46 ″Revs/Mile 738.5Circum. 85.8″
Tire 1
Specification
Tire 2
26.86"
Diameter
27.31"
8.86"
Width
8.46"
4.43"
Sidewall
4.66"
84.378"
Circum.
85.8"
750.9
Revs/Mile
738.5

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