How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.8%

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

2.8%

Absolute Difference

0.79"

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
2020.6+0.6
3030.8+0.8
4041.1+1.1
5051.4+1.4
6061.7+1.7
7072+2
8082.2+2.2
Tire 1Dia. 28.25 ″Rim 19 ″4.63 ″Width 9.25 ″Revs/Mile 713.9Circum. 88.8″Tire 2Dia. 29.04 ″Rim 19 ″5.02 ″Width 10.04 ″Revs/Mile 694.5Circum. 91.2″
Tire 1
Specification
Tire 2
28.25"
Diameter
29.04"
9.25"
Width
10.04"
4.63"
Sidewall
5.02"
88.756"
Circum.
91.23"
713.9
Revs/Mile
694.5

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