How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.05%

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

-1.05%

Absolute Difference

-0.33"

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. 31.34 ″Rim 19 ″6.17 ″Width 11.22 ″Revs/Mile 643.5Circum. 98.5″Tire 2Dia. 31.01 ″Rim 19 ″6.00 ″Width 12.01 ″Revs/Mile 650.4Circum. 97.4″
Tire 1
Specification
Tire 2
31.34"
Diameter
31.01"
11.22"
Width
12.01"
6.17"
Sidewall
6"
98.465"
Circum.
97.414"
643.5
Revs/Mile
650.4

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