How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.01%

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

-1.01%

Absolute Difference

-0.32"

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
2019.8-0.2
3029.7-0.3
4039.6-0.4
5049.5-0.5
6059.4-0.6
7069.3-0.7
8079.2-0.8
Tire 1Dia. 31.61 ″Rim 22 ″4.80 ″Width 12.01 ″Revs/Mile 638.1Circum. 99.3″Tire 2Dia. 31.29 ″Rim 22 ″4.65 ″Width 11.61 ″Revs/Mile 644.5Circum. 98.3″
Tire 1
Specification
Tire 2
31.61"
Diameter
31.29"
12.01"
Width
11.61"
4.8"
Sidewall
4.65"
99.294"
Circum.
98.305"
638.1
Revs/Mile
644.5

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