How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-0.91%

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

-0.91%

Absolute Difference

-0.26"

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
2019.8-0.2
3029.7-0.3
4039.6-0.4
5049.5-0.5
6059.5-0.5
7069.4-0.6
8079.3-0.7
Tire 1Dia. 28.65 ″Rim 19 ″4.82 ″Width 9.65 ″Revs/Mile 704.1Circum. 90.0″Tire 2Dia. 28.39 ″Rim 19 ″4.69 ″Width 10.43 ″Revs/Mile 710.4Circum. 89.2″
Tire 1
Specification
Tire 2
28.65"
Diameter
28.39"
9.65"
Width
10.43"
4.82"
Sidewall
4.69"
89.993"
Circum.
89.189"
704.1
Revs/Mile
710.4

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