How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.94%

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

1.94%

Absolute Difference

0.55"

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
2020.4+0.4
3030.6+0.6
4040.8+0.8
5051+1
6061.2+1.2
7071.4+1.4
8081.5+1.5
Tire 1Dia. 28.40 ″Rim 16 ″6.20 ″Width 8.86 ″Revs/Mile 710.1Circum. 89.2″Tire 2Dia. 28.95 ″Rim 16 ″6.48 ″Width 9.25 ″Revs/Mile 696.6Circum. 91.0″
Tire 1
Specification
Tire 2
28.4"
Diameter
28.95"
8.86"
Width
9.25"
6.2"
Sidewall
6.48"
89.226"
Circum.
90.958"
710.1
Revs/Mile
696.6

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