Tire Size Decoder
Decode one tire size and calculate theoretical dimensions before comparing two sizes.
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Tire Size Comparison Tool
Compare two tire sizes using theoretical unloaded dimensions. This is a reference tool, not a fitment approval tool.
Compare tire sizes
Not sure what the size markings mean? Decode a tire size first, then return here to compare two sizes.
Related Tire Size Resources
How Tire Sizing Works
Learn what the width, aspect ratio, construction, rim diameter, load index, and speed rating mean.
Read the guideSpeedometer Difference
Learn why diameter changes can affect speedometer and odometer readings.
Learn moreFrequently asked questions
What does tire diameter difference mean?
Tire diameter difference is the theoretical overall diameter change between two unloaded tire sizes. It can affect speedometer accuracy, vehicle clearance, gearing, ABS behavior, traction control calibration, and drivetrain operation.
Why are tire size comparison calculations theoretical?
The calculations use standard unloaded tire size formulas. Actual mounted and loaded tire dimensions vary by tire manufacturer, wheel width, inflation pressure, vehicle load, tire construction, tread depth, and operating conditions.
Can changing tire size affect speedometer accuracy?
Yes. A tire with a different overall diameter changes the number of tire revolutions per mile, which can affect speedometer and odometer readings.
Does a larger tire always fit safely?
No. Fitment depends on vehicle clearance, wheel width, suspension geometry, load rating, speed rating, inflation pressure, and vehicle manufacturer recommendations.
Is this tool a fitment approval system?
No. Treadsley tools are informational reference utilities only and do not replace vehicle manufacturer guidance or qualified tire and service inspection.
Important disclaimer
Treadsley tire size comparison results are theoretical unloaded calculations only. Actual installed tire dimensions and rolling radius may vary due to load, inflation pressure, wheel width, tread design, tread depth, manufacturing tolerances, casing construction, wear, and vehicle operating conditions.
Always verify replacement tire sizes against the tire information placard, owner’s manual, or vehicle manufacturer recommendations for your specific vehicle and wheel configuration. Treadsley provides informational reference data only and does not guarantee tire fitment, safety, vehicle compatibility, legal compliance, speedometer accuracy, clearance, handling, ABS/traction-control behavior, or performance.