How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.99%

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

-1.99%

Absolute Difference

-0.65"

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
2019.6-0.4
3029.4-0.6
4039.2-0.8
5049-1
6058.8-1.2
7068.6-1.4
8078.4-1.6
Tire 1Dia. 32.59 ″Rim 18 ″7.29 ″Width 11.22 ″Revs/Mile 618.9Circum. 102.4″Tire 2Dia. 31.94 ″Rim 18 ″6.97 ″Width 11.61 ″Revs/Mile 631.5Circum. 100.3″
Tire 1
Specification
Tire 2
32.59"
Diameter
31.94"
11.22"
Width
11.61"
7.29"
Sidewall
6.97"
102.374"
Circum.
100.333"
618.9
Revs/Mile
631.5

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