How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.7%

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

-1.7%

Absolute Difference

-0.51"

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
3029.5-0.5
4039.3-0.7
5049.2-0.8
6059-1
7068.8-1.2
8078.6-1.4
Tire 1Dia. 30.05 ″Rim 17 ″6.53 ″Width 10.04 ″Revs/Mile 671.1Circum. 94.4″Tire 2Dia. 29.54 ″Rim 17 ″6.27 ″Width 9.65 ″Revs/Mile 682.8Circum. 92.8″
Tire 1
Specification
Tire 2
30.05"
Diameter
29.54"
10.04"
Width
9.65"
6.53"
Sidewall
6.27"
94.409"
Circum.
92.801"
671.1
Revs/Mile
682.8

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