How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.04%

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

-2.04%

Absolute Difference

-0.51"

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. 24.98 ″Rim 15 ″4.99 ″Width 7.68 ″Revs/Mile 807.4Circum. 78.5″Tire 2Dia. 24.47 ″Rim 15 ″4.73 ″Width 7.28 ″Revs/Mile 824.2Circum. 76.9″
Tire 1
Specification
Tire 2
24.98"
Diameter
24.47"
7.68"
Width
7.28"
4.99"
Sidewall
4.73"
78.478"
Circum.
76.87"
807.4
Revs/Mile
824.2

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