How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.89%

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

1.89%

Absolute Difference

0.49"

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
2020.4+0.4
3030.6+0.6
4040.8+0.8
5050.9+0.9
6061.1+1.1
7071.3+1.3
8081.5+1.5
Tire 1Dia. 25.97 ″Rim 18 ″3.99 ″Width 8.86 ″Revs/Mile 776.5Circum. 81.6″Tire 2Dia. 26.46 ″Rim 18 ″4.23 ″Width 8.46 ″Revs/Mile 762.1Circum. 83.1″
Tire 1
Specification
Tire 2
25.97"
Diameter
26.46"
8.86"
Width
8.46"
3.99"
Sidewall
4.23"
81.595"
Circum.
83.141"
776.5
Revs/Mile
762.1

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