Enter your original tire/wheel specs — tire width, aspect ratio, wheel diameter, and offset — then plug in your new tire dimensions to find out how much fender trimming your swap requires, plus outward/inward movement and overall diameter change.
Fender Trimming Required
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Outward Movement
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Inward Movement
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Overall Diameter Change
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Clearance Status
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Fender trimming involves cutting or rolling the inner fender liner to create clearance for larger tires. It's needed when upgrading to wider tires or wheels with different offsets that would otherwise rub against the fender at full steering lock.
Wheel offset is usually stamped on the back of the wheel. Look for markings like 'ET40' which means 40mm positive offset. You can also measure from the wheel's mounting surface to the centerline of the wheel.
Proper fender trimming typically doesn't affect safety as it only removes inner liner material. However, it may void certain warranty coverage, so check with your dealer before modifications.
Spacers push wheels outward which can actually make rubbing worse. They're useful for fine-tuning fitment but won't help with clearance issues that require trimming.
Offset is the distance from the wheel's mounting surface to its centerline (can be positive or negative). Backspacing is the distance from the mounting surface to the inner edge of the wheel (always positive).
This calculator provides estimates based on wheel and tire dimensions. Actual clearance can vary due to suspension geometry, ride height, and manufacturing tolerances. Always test fit before final installation.