How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-0.64%

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

-0.64%

Absolute Difference

-0.21"

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
2019.9-0.1
3029.8-0.2
4039.7-0.3
5049.7-0.3
6059.6-0.4
7069.6-0.4
8079.5-0.5
Tire 1Dia. 32.99 ″Rim 20 ″6.50 ″Width 10.83 ″Revs/Mile 611.3Circum. 103.6″Tire 2Dia. 32.78 ″Rim 20 ″6.39 ″Width 11.61 ″Revs/Mile 615.3Circum. 103.0″
Tire 1
Specification
Tire 2
32.99"
Diameter
32.78"
10.83"
Width
11.61"
6.5"
Sidewall
6.39"
103.648"
Circum.
102.968"
611.3
Revs/Mile
615.3

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