How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.64%

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

-2.64%

Absolute Difference

-0.76"

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
3029.2-0.8
4038.9-1.1
5048.7-1.3
6058.4-1.6
7068.1-1.9
8077.9-2.1
Tire 1Dia. 28.74 ″Rim 19 ″4.87 ″Width 10.83 ″Revs/Mile 701.6Circum. 90.3″Tire 2Dia. 27.98 ″Rim 19 ″4.49 ″Width 11.22 ″Revs/Mile 720.9Circum. 87.9″
Tire 1
Specification
Tire 2
28.74"
Diameter
27.98"
10.83"
Width
11.22"
4.87"
Sidewall
4.49"
90.302"
Circum.
87.89"
701.6
Revs/Mile
720.9

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