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
2019.4-0.6
3029.2-0.8
4038.9-1.1
5048.6-1.4
6058.3-1.7
7068-2
8077.8-2.2
Tire 1Dia. 28.25 ″Rim 19 ″4.63 ″Width 9.25 ″Revs/Mile 713.9Circum. 88.8″Tire 2Dia. 27.46 ″Rim 19 ″4.23 ″Width 8.46 ″Revs/Mile 734.3Circum. 86.3″
Tire 1
Specification
Tire 2
28.25"
Diameter
27.46"
9.25"
Width
8.46"
4.63"
Sidewall
4.23"
88.756"
Circum.
86.282"
713.9
Revs/Mile
734.3

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