Are you facing the common issue of tire rubbing on your cherished vehicle, especially after upgrading to a wider tire and wheel setup? Many car enthusiasts and race car drivers encounter this problem, where the tires make unwelcome contact with the existing bodywork, particularly the fenders. One quick but often unsightly solution is to cut into the fenders and bolt on makeshift plates, but this compromises aerodynamics and aesthetics, and may not even fully resolve the rubbing.
This guide offers a more refined and effective approach to modify your fenders, utilizing Simple Car Parts and readily available materials to create seamless, performance-oriented fender extensions. Inspired by a modification project on a Ralt R5 CSR Mazda race car, we’ll walk you through the process of crafting new fender sections that integrate smoothly with your existing bodywork, eliminating tire rub and enhancing your vehicle’s appearance. While we may not have photos for every single step of the original project, detailed descriptions and illustrations will provide a clear path to achieving professional-looking results in your own garage.
Step-by-Step Guide to Fender Modification
1. Determining Fender Line and Creating a Foam Template
The first crucial step is to visualize and decide how much higher you need to raise the fender line to achieve adequate tire clearance. Once you have this measurement, create a template using cardboard or stiff paper that reflects the desired shape of your new fender extension. This template will serve as a guide for cutting the blue foam, a lightweight and easily workable material ideal for shaping bodywork modifications.
Alt text: Blue foam template outlines the desired extension for a car fender modification, showcasing a simple car part used in auto body repair.
2. Cutting and Fitting the Blue Foam
Using the template, carefully cut the blue foam to shape. A hot wire cutter is highly recommended for achieving clean and precise cuts in foam. Once cut, place the foam piece on top of the existing fender to check the fit and ensure it aligns with your envisioned fender line. Refine the foam shape as needed until you are satisfied with the fit and contour.
Alt text: Hot wire cutter precisely shapes blue foam, a simple car part, to create a custom fender extension for automotive bodywork.
3. Securing Foam and Creating Vents
Once the foam fits perfectly, secure it to the fender using clear packing tape. The tape acts as a barrier, preventing the polyester resin used in fiberglassing from melting the foam. If you desire vents in your new fender design, now is the time to create them. Wood molding or similar easily shaped materials can be hot-glued onto the taped foam to form the vent shapes.
Alt text: Clear packing tape secures blue foam to car fender, with wood molding, simple car parts, hot-glued to create custom vent features.
4. Applying Mold Release Wax
To ensure easy removal of the fiberglass mold later, apply a generous coating of mold release wax over the taped foam and any vent moldings. This wax creates a non-stick surface, preventing the fiberglass resin from bonding to the foam.
Alt text: Applying mold release wax, a simple car part in bodywork, to taped foam in preparation for fiberglass fender molding.
5. Fiberglass Application
Now comes the fiberglassing stage. Wet fiberglass cloth with polyester resin. Remember, if using chopped strand mat (CSM), polyester resin is necessary as epoxy resin will not properly dissolve the binder in CSM. For woven fiberglass cloth, either polyester or epoxy resin can be used. Apply the resin-soaked fiberglass cloth over the foam mold. You can use either woven fiberglass cloth or chopped strand mat, depending on your preference and desired strength.
Alt text: Applying fiberglass cloth and polyester resin, simple car parts for DIY, onto a blue foam mold to create a custom fender extension.
Pro Tip: When working with woven cloth, pre-cutting the cloth and lightly adhering it to your pattern with 3M Super77 spray adhesive can simplify the process. Then, wet out the cloth with resin using a short bristled brush. If you need to apply fiberglass in sections, ensure overlaps of at least one inch for structural integrity.
6. Mold Curing and Removal
Allow the polyester resin to fully cure. Once cured, carefully pull the fiberglass mold away from the foam pattern. The foam can be broken away or dissolved if necessary, leaving you with a durable fiberglass mold of your new fender section.
Alt text: Cured fiberglass mold, a simple car part created through DIY process, detached from the blue foam fender pattern.
7. (Optional) Carbon Fiber Molding
For enhanced stiffness and a high-performance aesthetic, you can create a carbon fiber positive from the fiberglass mold. First, apply mold release wax to the inner surface of the fiberglass mold. Then, begin layering carbon fiber cloth inside the mold, wetting each layer with resin. Epoxy resin is generally preferred for carbon fiber lamination due to its superior stiffness.
Alt text: Layering carbon fiber cloth, a simple car part upgrade, inside a fiberglass mold using epoxy resin for enhanced fender stiffness.
Layering Technique: Alternate the orientation of carbon fiber layers at 45/90 degrees. Woven carbon fiber is directional in stiffness, and this alternating pattern maximizes overall strength. Use a short bristled brush and a stippling motion to ensure thorough resin penetration into the carbon fiber weave.
8. Trimming and Demolding Carbon Fiber
Before the carbon fiber resin fully cures, trim any excess material around the mold edges with scissors. This is much easier to do at this stage than after full curing. Once fully cured, carefully remove the carbon fiber part from the fiberglass mold.
Alt text: Trimming excess carbon fiber material, a simple car part component, from the fiberglass mold edge before the resin fully cures.
9. Bonding and Finishing
With your new fiberglass or carbon fiber fender sections molded, the final step is bonding them to the existing bodywork. Use a suitable automotive body panel adhesive for secure attachment. Once bonded, blend the new sections seamlessly into the existing bodywork using body filler and standard bodywork finishing techniques to achieve a professional, factory-like finish.
Alt text: Finished carbon fiber fender extension, a simple car part modification, bonded and blended to car bodywork with filler for seamless integration.
Conclusion
Modifying your car’s fenders to accommodate larger wheels and tires doesn’t have to be a complex or expensive endeavor. By utilizing simple car parts, readily available materials, and these step-by-step techniques, you can achieve professional-looking fender extensions that enhance both the performance and aesthetics of your vehicle. Whether you choose fiberglass or opt for the added stiffness and visual appeal of carbon fiber, this DIY approach offers a rewarding path to customizing your ride and overcoming tire rubbing issues.
