How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.82%

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

1.82%

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
2020.4+0.4
3030.5+0.5
4040.7+0.7
5050.9+0.9
6061.1+1.1
7071.3+1.3
8081.5+1.5
Tire 1Dia. 24.21 ″Rim 15 ″4.61 ″Width 7.68 ″Revs/Mile 833.0Circum. 76.1″Tire 2Dia. 24.65 ″Rim 15 ″4.82 ″Width 6.89 ″Revs/Mile 818.3Circum. 77.4″
Tire 1
Specification
Tire 2
24.21"
Diameter
24.65"
7.68"
Width
6.89"
4.61"
Sidewall
4.82"
76.066"
Circum.
77.427"
833
Revs/Mile
818.3

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