How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.9%

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

2.9%

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
2020.6+0.6
3030.9+0.9
4041.2+1.2
5051.4+1.4
6061.7+1.7
7072+2
8082.3+2.3
Tire 1Dia. 27.25 ″Rim 18 ″4.63 ″Width 9.25 ″Revs/Mile 740.1Circum. 85.6″Tire 2Dia. 28.04 ″Rim 18 ″5.02 ″Width 10.04 ″Revs/Mile 719.3Circum. 88.1″
Tire 1
Specification
Tire 2
27.25"
Diameter
28.04"
9.25"
Width
10.04"
4.63"
Sidewall
5.02"
85.615"
Circum.
88.088"
740.1
Revs/Mile
719.3

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