How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.77%

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

2.77%

Absolute Difference

0.75"

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
3030.8+0.8
4041.1+1.1
5051.4+1.4
6061.7+1.7
7071.9+1.9
8082.2+2.2
Tire 1Dia. 27.10 ″Rim 16 ″5.55 ″Width 9.25 ″Revs/Mile 744.1Circum. 85.1″Tire 2Dia. 27.85 ″Rim 16 ″5.93 ″Width 8.46 ″Revs/Mile 724.2Circum. 87.5″
Tire 1
Specification
Tire 2
27.1"
Diameter
27.85"
9.25"
Width
8.46"
5.55"
Sidewall
5.93"
85.145"
Circum.
87.495"
744.1
Revs/Mile
724.2

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