How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

-2.79%

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

-2.79%

Absolute Difference

-0.75"

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
2019.4-0.6
3029.2-0.8
4038.9-1.1
5048.6-1.4
6058.3-1.7
7068-2
8077.8-2.2
Tire 1Dia. 26.85 ″Rim 15 ″5.93 ″Width 8.46 ″Revs/Mile 751.1Circum. 84.4″Tire 2Dia. 26.10 ″Rim 15 ″5.55 ″Width 9.25 ″Revs/Mile 772.7Circum. 82.0″
Tire 1
Specification
Tire 2
26.85"
Diameter
26.1"
8.46"
Width
9.25"
5.93"
Sidewall
5.55"
84.353"
Circum.
82.003"
751.1
Revs/Mile
772.7

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