How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-0.59%

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

-0.59%

Absolute Difference

-0.18"

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
2019.9-0.1
3029.8-0.2
4039.8-0.2
5049.7-0.3
6059.6-0.4
7069.6-0.4
8079.5-0.5
Tire 1Dia. 30.52 ″Rim 18 ″6.26 ″Width 10.43 ″Revs/Mile 660.8Circum. 95.9″Tire 2Dia. 30.34 ″Rim 18 ″6.17 ″Width 11.22 ″Revs/Mile 664.7Circum. 95.3″
Tire 1
Specification
Tire 2
30.52"
Diameter
30.34"
10.43"
Width
11.22"
6.26"
Sidewall
6.17"
95.88"
Circum.
95.324"
660.8
Revs/Mile
664.7

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