How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.26%

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

-1.26%

Absolute Difference

-0.37"

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
2019.7-0.3
3029.6-0.4
4039.5-0.5
5049.4-0.6
6059.2-0.8
7069.1-0.9
8079-1
Tire 1Dia. 29.40 ″Rim 17 ″6.20 ″Width 8.86 ″Revs/Mile 686.0Circum. 92.4″Tire 2Dia. 29.03 ″Rim 17 ″6.01 ″Width 9.25 ″Revs/Mile 694.8Circum. 91.2″
Tire 1
Specification
Tire 2
29.4"
Diameter
29.03"
8.86"
Width
9.25"
6.2"
Sidewall
6.01"
92.368"
Circum.
91.193"
686
Revs/Mile
694.8

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