How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.66%

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

2.66%

Absolute Difference

0.71"

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
2020.5+0.5
3030.8+0.8
4041.1+1.1
5051.3+1.3
6061.6+1.6
7071.9+1.9
8082.1+2.1
Tire 1Dia. 26.68 ″Rim 18 ″4.34 ″Width 9.65 ″Revs/Mile 755.9Circum. 83.8″Tire 2Dia. 27.39 ″Rim 18 ″4.69 ″Width 10.43 ″Revs/Mile 736.3Circum. 86.0″
Tire 1
Specification
Tire 2
26.68"
Diameter
27.39"
9.65"
Width
10.43"
4.34"
Sidewall
4.69"
83.821"
Circum.
86.047"
755.9
Revs/Mile
736.3

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