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

-0.77"

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. 30.22 ″Rim 19 ″5.61 ″Width 11.22 ″Revs/Mile 667.4Circum. 94.9″Tire 2Dia. 29.45 ″Rim 19 ″5.23 ″Width 11.61 ″Revs/Mile 684.8Circum. 92.5″
Tire 1
Specification
Tire 2
30.22"
Diameter
29.45"
11.22"
Width
11.61"
5.61"
Sidewall
5.23"
94.94"
Circum.
92.529"
667.4
Revs/Mile
684.8

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