How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.82%

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

2.82%

Absolute Difference

0.86"

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
2020.6+0.6
3030.8+0.8
4041.1+1.1
5051.4+1.4
6061.7+1.7
7072+2
8082.3+2.3
Tire 1Dia. 30.48 ″Rim 19 ″5.74 ″Width 10.43 ″Revs/Mile 661.8Circum. 95.7″Tire 2Dia. 31.34 ″Rim 19 ″6.17 ″Width 11.22 ″Revs/Mile 643.5Circum. 98.5″
Tire 1
Specification
Tire 2
30.48"
Diameter
31.34"
10.43"
Width
11.22"
5.74"
Sidewall
6.17"
95.744"
Circum.
98.465"
661.8
Revs/Mile
643.5

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