How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-1.86%

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

-1.86%

Absolute Difference

-0.55"

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
2019.6-0.4
3029.4-0.6
4039.3-0.7
5049.1-0.9
6058.9-1.1
7068.7-1.3
8078.5-1.5
Tire 1Dia. 29.50 ″Rim 16 ″6.75 ″Width 9.65 ″Revs/Mile 683.6Circum. 92.7″Tire 2Dia. 28.95 ″Rim 16 ″6.48 ″Width 9.25 ″Revs/Mile 696.6Circum. 91.0″
Tire 1
Specification
Tire 2
29.5"
Diameter
28.95"
9.65"
Width
9.25"
6.75"
Sidewall
6.48"
92.689"
Circum.
90.958"
683.6
Revs/Mile
696.6

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