How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.98%

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

1.98%

Absolute Difference

0.48"

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
2020.4+0.4
3030.6+0.6
4040.8+0.8
5051+1
6061.2+1.2
7071.4+1.4
8081.6+1.6
Tire 1Dia. 24.21 ″Rim 15 ″4.61 ″Width 7.68 ″Revs/Mile 833.0Circum. 76.1″Tire 2Dia. 24.69 ″Rim 15 ″4.84 ″Width 8.07 ″Revs/Mile 817.0Circum. 77.5″
Tire 1
Specification
Tire 2
24.21"
Diameter
24.69"
7.68"
Width
8.07"
4.61"
Sidewall
4.84"
76.066"
Circum.
77.55"
833
Revs/Mile
817

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