How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.91%

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

-2.91%

Absolute Difference

-0.87"

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
2019.4-0.6
3029.1-0.9
4038.8-1.2
5048.5-1.5
6058.3-1.7
7068-2
8077.7-2.3
Tire 1Dia. 29.91 ″Rim 18 ″5.95 ″Width 10.83 ″Revs/Mile 674.3Circum. 94.0″Tire 2Dia. 29.04 ″Rim 18 ″5.52 ″Width 10.04 ″Revs/Mile 694.4Circum. 91.2″
Tire 1
Specification
Tire 2
29.91"
Diameter
29.04"
10.83"
Width
10.04"
5.95"
Sidewall
5.52"
93.963"
Circum.
91.242"
674.3
Revs/Mile
694.4

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