How it works

TireFlows

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

Tire 1
/R
Tire 2
/R

Result

Diameter Difference

2.05%

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

2.05%

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
2020.4+0.4
3030.6+0.6
4040.8+0.8
5051+1
6061.2+1.2
7071.4+1.4
8081.6+1.6
Tire 1Dia. 26.85 ″Rim 15 ″5.93 ″Width 8.46 ″Revs/Mile 751.1Circum. 84.4″Tire 2Dia. 27.40 ″Rim 15 ″6.20 ″Width 8.86 ″Revs/Mile 736.0Circum. 86.1″
Tire 1
Specification
Tire 2
26.85"
Diameter
27.4"
8.46"
Width
8.86"
5.93"
Sidewall
6.2"
84.353"
Circum.
86.085"
751.1
Revs/Mile
736

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