How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.55%

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

1.55%

Absolute Difference

0.42"

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
3030.5+0.5
4040.6+0.6
5050.8+0.8
6060.9+0.9
7071.1+1.1
8081.2+1.2
Tire 1Dia. 27.10 ″Rim 16 ″5.55 ″Width 9.25 ″Revs/Mile 744.1Circum. 85.1″Tire 2Dia. 27.52 ″Rim 16 ″5.76 ″Width 8.86 ″Revs/Mile 733.0Circum. 86.4″
Tire 1
Specification
Tire 2
27.1"
Diameter
27.52"
9.25"
Width
8.86"
5.55"
Sidewall
5.76"
85.145"
Circum.
86.443"
744.1
Revs/Mile
733

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