How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

0.6%

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

0.6%

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
2020.1+0.1
3030.2+0.2
4040.2+0.2
5050.3+0.3
6060.4+0.4
7070.4+0.4
8080.5+0.5
Tire 1Dia. 29.88 ″Rim 16 ″6.94 ″Width 9.25 ″Revs/Mile 675.0Circum. 93.9″Tire 2Dia. 30.06 ″Rim 16 ″7.03 ″Width 10.04 ″Revs/Mile 671.0Circum. 94.4″
Tire 1
Specification
Tire 2
29.88"
Diameter
30.06"
9.25"
Width
10.04"
6.94"
Sidewall
7.03"
93.864"
Circum.
94.421"
675
Revs/Mile
671

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