How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.36%

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

1.36%

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
4040.5+0.5
5050.7+0.7
6060.8+0.8
7071+1
8081.1+1.1
Tire 1Dia. 32.34 ″Rim 20 ″6.17 ″Width 11.22 ″Revs/Mile 623.6Circum. 101.6″Tire 2Dia. 32.78 ″Rim 20 ″6.39 ″Width 11.61 ″Revs/Mile 615.3Circum. 103.0″
Tire 1
Specification
Tire 2
32.34"
Diameter
32.78"
11.22"
Width
11.61"
6.17"
Sidewall
6.39"
101.607"
Circum.
102.968"
623.6
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