How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.55%

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

-2.55%

Absolute Difference

-0.67"

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
4039-1
5048.7-1.3
6058.5-1.5
7068.2-1.8
8078-2
Tire 1Dia. 26.30 ″Rim 15 ″5.65 ″Width 8.07 ″Revs/Mile 766.9Circum. 82.6″Tire 2Dia. 25.63 ″Rim 15 ″5.31 ″Width 8.86 ″Revs/Mile 786.9Circum. 80.5″
Tire 1
Specification
Tire 2
26.3"
Diameter
25.63"
8.07"
Width
8.86"
5.65"
Sidewall
5.31"
82.621"
Circum.
80.519"
766.9
Revs/Mile
786.9

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