Diagnosis
The plastic fender is a known weak point. Cracks from stress or impacts cause it to vibrate against the tire or frame.
How to Fix It
Secure the fender temporarily to diagnose, then plan for replacement.
- First, clean the area. Identify where the crack is and where it's contacting the tire.
- Use strong, waterproof tape (like Gorilla Tape) or a zip tie to tightly bind the cracked sections together and pull the fender away from the tire. Wrap tape around the entire fender width for best hold.
- Test ride. If the rattle is gone, you've confirmed the source.
If That Didn't Work
The rattle might be from the fender's metal mounting bracket loosening. Tighten the two bolts that secure the bracket to the frame under the deck. Don't overtighten and crack the plastic further.
Heads Up
A cracked fender close to the tire is a safety risk—it can catch the tire and lock the wheel. Consider ordering a replacement fender (often sold as a "mudguard") and installing it. The permanent fix requires removing the rear wheel.