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
2019.5-0.5
3029.2-0.8
4038.9-1.1
5048.7-1.3
6058.4-1.6
7068.1-1.9
8077.9-2.1
Tire 1Dia. 26.68 ″Rim 18 ″4.34 ″Width 9.65 ″Revs/Mile 755.9Circum. 83.8″Tire 2Dia. 25.97 ″Rim 18 ″3.99 ″Width 8.86 ″Revs/Mile 776.5Circum. 81.6″
Tire 1
Specification
Tire 2
26.68"
Diameter
25.97"
9.65"
Width
8.86"
4.34"
Sidewall
3.99"
83.821"
Circum.
81.595"
755.9
Revs/Mile
776.5

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