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Free Tire Size Calculator & Comparison Tool | Speedometer Error Calculator

/tire-size
Free online tire size calculator and comparison tool. Compare tire sizes, calculate speedometer error, and determine if your new tire size is safe. Instantly calculate diameter differences, speedometer accuracy, and get safety recommendations based on industry standards. Perfect for tire upgrades, plus sizing, and wheel fitment. Calculate tire size differences for cars, trucks, SUVs, and performance vehicles.
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Parameters

current undefined
Current tire size (format: width/aspect/rim, e.g., 225/45/17)
proposed undefined
Proposed tire size (format: width/aspect/rim, e.g., 235/45/18)

Examples

curl 
curl 'https://tcpdata.com/tire-size?current=225/45/17&proposed=235/45/18'
curl 
curl 'https://tcpdata.com/tire-size?current=205/55/16&proposed=215/50/17'

Notes

Tire size format: width (mm) / aspect ratio (%) / rim diameter (inches)

Valid ranges: Width 125-335mm, Aspect ratio 25-85%, Rim diameter 13-24 inches

Safety thresholds based on overall diameter difference:

• ±0-3%: Safe - Within acceptable range

• ±3-5%: Caution - May affect speedometer accuracy and fuel economy

• >±5%: Not Recommended - Can cause speedometer error, affect ABS/traction control, and may cause rubbing

Speedometer error calculated at 60 mph actual speed for reference