How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.86%

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

1.86%

Absolute Difference

0.52"

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
4040.7+0.7
5050.9+0.9
6061.1+1.1
7071.3+1.3
8081.5+1.5
Tire 1Dia. 28.00 ″Rim 17 ″5.50 ″Width 8.46 ″Revs/Mile 720.2Circum. 88.0″Tire 2Dia. 28.52 ″Rim 17 ″5.76 ″Width 8.86 ″Revs/Mile 707.3Circum. 89.6″
Tire 1
Specification
Tire 2
28"
Diameter
28.52"
8.46"
Width
8.86"
5.5"
Sidewall
5.76"
87.977"
Circum.
89.585"
720.2
Revs/Mile
707.3

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