How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

1.87%

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

1.87%

Absolute Difference

0.57"

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
2020.4+0.4
3030.6+0.6
4040.7+0.7
5050.9+0.9
6061.1+1.1
7071.3+1.3
8081.5+1.5
Tire 1Dia. 30.48 ″Rim 19 ″5.74 ″Width 10.43 ″Revs/Mile 661.8Circum. 95.7″Tire 2Dia. 31.05 ″Rim 19 ″6.02 ″Width 10.04 ″Revs/Mile 649.6Circum. 97.5″
Tire 1
Specification
Tire 2
30.48"
Diameter
31.05"
10.43"
Width
10.04"
5.74"
Sidewall
6.02"
95.744"
Circum.
97.538"
661.8
Revs/Mile
649.6

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