How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.18%

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

2.18%

Absolute Difference

0.65"

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
3030.7+0.7
4040.9+0.9
5051.1+1.1
6061.3+1.3
7071.5+1.5
8081.7+1.7
Tire 1Dia. 29.83 ″Rim 19 ″5.41 ″Width 10.83 ″Revs/Mile 676.2Circum. 93.7″Tire 2Dia. 30.48 ″Rim 19 ″5.74 ″Width 10.43 ″Revs/Mile 661.8Circum. 95.7″
Tire 1
Specification
Tire 2
29.83"
Diameter
30.48"
10.83"
Width
10.43"
5.41"
Sidewall
5.74"
93.704"
Circum.
95.744"
676.2
Revs/Mile
661.8

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