How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

0.88%

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

0.88%

Absolute Difference

0.22"

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
2020.2+0.2
3030.3+0.3
4040.4+0.4
5050.4+0.4
6060.5+0.5
7070.6+0.6
8080.7+0.7
Tire 1Dia. 24.98 ″Rim 15 ″4.99 ″Width 7.68 ″Revs/Mile 807.4Circum. 78.5″Tire 2Dia. 25.20 ″Rim 15 ″5.10 ″Width 7.28 ″Revs/Mile 800.4Circum. 79.2″
Tire 1
Specification
Tire 2
24.98"
Diameter
25.2"
7.68"
Width
7.28"
4.99"
Sidewall
5.1"
78.478"
Circum.
79.158"
807.4
Revs/Mile
800.4

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