How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

0.07%

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

0.07%

Absolute Difference

0.02"

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
20200
30300
40400
50500
60600
70700
8080.1+0.1
Tire 1Dia. 28.61 ″Rim 18 ″5.31 ″Width 9.65 ″Revs/Mile 704.9Circum. 89.9″Tire 2Dia. 28.63 ″Rim 18 ″5.31 ″Width 8.86 ″Revs/Mile 704.4Circum. 89.9″
Tire 1
Specification
Tire 2
28.61"
Diameter
28.63"
9.65"
Width
8.86"
5.31"
Sidewall
5.31"
89.882"
Circum.
89.944"
704.9
Revs/Mile
704.4

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