How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.42%

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

-2.42%

Absolute Difference

-0.67"

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
2019.5-0.5
3029.3-0.7
4039-1
5048.8-1.2
6058.5-1.5
7068.3-1.7
8078.1-1.9
Tire 1Dia. 27.70 ″Rim 15 ″6.35 ″Width 8.46 ″Revs/Mile 728.2Circum. 87.0″Tire 2Dia. 27.03 ″Rim 15 ″6.01 ″Width 9.25 ″Revs/Mile 746.2Circum. 84.9″
Tire 1
Specification
Tire 2
27.7"
Diameter
27.03"
8.46"
Width
9.25"
6.35"
Sidewall
6.01"
87.012"
Circum.
84.91"
728.2
Revs/Mile
746.2

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