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
8079.9-0.1
Tire 1Dia. 29.18 ″Rim 19 ″5.09 ″Width 9.25 ″Revs/Mile 691.2Circum. 91.7″Tire 2Dia. 29.16 ″Rim 19 ″5.08 ″Width 8.46 ″Revs/Mile 691.7Circum. 91.6″
Tire 1
Specification
Tire 2
29.18"
Diameter
29.16"
9.25"
Width
8.46"
5.09"
Sidewall
5.08"
91.663"
Circum.
91.601"
691.2
Revs/Mile
691.7

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