How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.44%

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

2.44%

Absolute Difference

0.71"

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
2020.5+0.5
3030.7+0.7
4041+1
5051.2+1.2
6061.5+1.5
7071.7+1.7
8082+2
Tire 1Dia. 29.10 ″Rim 19 ″5.05 ″Width 11.22 ″Revs/Mile 693.1Circum. 91.4″Tire 2Dia. 29.81 ″Rim 19 ″5.40 ″Width 12.01 ″Revs/Mile 676.6Circum. 93.6″
Tire 1
Specification
Tire 2
29.1"
Diameter
29.81"
11.22"
Width
12.01"
5.05"
Sidewall
5.4"
91.415"
Circum.
93.642"
693.1
Revs/Mile
676.6

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