FAQ
Tire Size Tools FAQ
Quick answers to the most common fitment and calculation questions. Use the links below to jump into the calculators referenced in each answer.
How do I read a tire size like 205/55R16?+
205 is the section width in millimeters, 55 is the aspect ratio (percentage of width), R means radial, and 16 is the rim diameter in inches.
What tire size difference is generally acceptable?+
Keep overall diameter changes within about ±3% for daily driving. Between 3–5% is borderline and needs clearance checks; beyond 5% is not recommended.
How does tire size affect speedometer readings?+
A larger diameter travels farther per revolution, so the dash reads slower than actual speed; a smaller diameter reads faster. Use the speedometer calibration tool to quantify the difference.
How do wheel width and offset affect fitment?+
Offset moves the wheel in or out relative to the hub. Larger positive offset pulls the wheel inward; negative offset pushes it outward. Pair width and offset to keep inner clearance and outer poke in check.
Can I use a larger tire instead of my stock size?+
Maybe. Check diameter difference, wheel width suitability, and suspension/fender clearance. Our comparison tool flags acceptable, borderline, and not recommended ranges.
How do I convert flotation sizes like 33x12.5R15?+
Convert to metric equivalents (approx 318/75R15) before using the tire size calculator for consistent results.
Do you store my calculator inputs?+
Inputs stay in your browser for the session; we do not persist them after you leave the page.
Can I export or print results?+
Yes. Use the copy summary or PDF/report links where available to share with shops or friends.
Is TireSize.app free to use?+
Yes. Core calculators are free. We may add premium features later but will keep core safety tools accessible.
Who should I contact for data corrections?+
Email [email protected] with the size, source, and details. We appreciate corrections to keep information accurate.