How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.3%

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

1.3%

Absolute Difference

0.36"

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
2020.3+0.3
3030.4+0.4
4040.5+0.5
5050.7+0.7
6060.8+0.8
7070.9+0.9
8081+1
Tire 1Dia. 27.68 ″Rim 19 ″4.34 ″Width 9.65 ″Revs/Mile 728.6Circum. 87.0″Tire 2Dia. 28.04 ″Rim 19 ″4.52 ″Width 10.04 ″Revs/Mile 719.4Circum. 88.1″
Tire 1
Specification
Tire 2
27.68"
Diameter
28.04"
9.65"
Width
10.04"
4.34"
Sidewall
4.52"
86.963"
Circum.
88.076"
728.6
Revs/Mile
719.4

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