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

-0.33"

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
2019.7-0.3
3029.6-0.4
4039.5-0.5
5049.3-0.7
6059.2-0.8
7069-1
8078.9-1.1
Tire 1Dia. 24.21 ″Rim 15 ″4.61 ″Width 7.68 ″Revs/Mile 833.0Circum. 76.1″Tire 2Dia. 23.88 ″Rim 15 ″4.44 ″Width 8.07 ″Revs/Mile 844.6Circum. 75.0″
Tire 1
Specification
Tire 2
24.21"
Diameter
23.88"
7.68"
Width
8.07"
4.61"
Sidewall
4.44"
76.066"
Circum.
75.015"
833
Revs/Mile
844.6

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