How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.09%

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

2.09%

Absolute Difference

0.55"

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
5051+1
6061.3+1.3
7071.5+1.5
8081.7+1.7
Tire 1Dia. 26.30 ″Rim 15 ″5.65 ″Width 8.07 ″Revs/Mile 766.9Circum. 82.6″Tire 2Dia. 26.85 ″Rim 15 ″5.93 ″Width 8.46 ″Revs/Mile 751.1Circum. 84.4″
Tire 1
Specification
Tire 2
26.3"
Diameter
26.85"
8.07"
Width
8.46"
5.65"
Sidewall
5.93"
82.621"
Circum.
84.353"
766.9
Revs/Mile
751.1

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