How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.4%

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

1.4%

Absolute Difference

0.44"

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
2020.3+0.3
3030.4+0.4
4040.6+0.6
5050.7+0.7
6060.8+0.8
7071+1
8081.1+1.1
Tire 1Dia. 31.34 ″Rim 19 ″6.17 ″Width 11.22 ″Revs/Mile 643.5Circum. 98.5″Tire 2Dia. 31.78 ″Rim 19 ″6.39 ″Width 11.61 ″Revs/Mile 634.7Circum. 99.8″
Tire 1
Specification
Tire 2
31.34"
Diameter
31.78"
11.22"
Width
11.61"
6.17"
Sidewall
6.39"
98.465"
Circum.
99.826"
643.5
Revs/Mile
634.7

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