How to Make a Carbon Rim

Step 1: Sourcing Raw Materials

We source all our carbon prepregs, release agents, and other raw manufacturing materials from reliable suppliers. They are then shipped, received, sorted, and stored with care within our facilities. Carbon prepregs are carbon fibers saturated with epoxy resin, and kept in optimal condition through refrigeration at -5℃: a stable temperature for the resin. We record and track every material batch and adhere to the “first-in, first-out” principle for quality consistency and waste reduction.

Step 2: Cutting to Size

According to the predetermined layup schedule and batch quantities, we select the necessary carbon sheets of required tensile strengths, FAWs, and weaves. Unidirectional carbon fiber sheets are cut into the desired angles of 0°, ±45°,±30°, and ±90°. The carbon fibers are precisely machine-cut into smaller pieces. For some complex shapes, we have an automated cutting process where the material is cut with curves, grooves, and hooks.

Step 3: Lamination

Lamination is a crucial part of material preparation at Light Bicycle. To facilitate the hand layup process in the rim mold, we execute some layup in advance on a flat surface. Lamination prepares the fabric laminates for different parts of the rim with the carbon sheets overlaid in the desired order and orientation, which allows us to manipulate the product more easily. A great example of this in practice is our innovative stepwise lamination - designed for weight saving and durability - which consists of carbon pieces overlapped with their edges recessed. This attention to detail is what proudly sets us apart from many manufacturers.

Step 1: Sourcing Raw Materials

We source all our carbon prepregs, release agents, and other raw manufacturing materials from reliable suppliers. They are then shipped, received, sorted, and stored with care within our facilities. Carbon prepregs are carbon fibers saturated with epoxy resin, and kept in optimal condition through refrigeration at -5℃: a stable temperature for the resin. We record and track every material batch and adhere to the “first-in, first-out” principle for quality consistency and waste reduction.

Step 2: Cutting to Size

According to the predetermined layup schedule and batch quantities, we select the necessary carbon sheets of required tensile strengths, FAWs, and weaves. Unidirectional carbon fiber sheets are cut into the desired angles of 0°, ±45°,±30°, and ±90°. The carbon fibers are precisely machine-cut into smaller pieces. For some complex shapes, we have an automated cutting process where the material is cut with curves, grooves, and hooks.

Step 3: Lamination

Lamination is a crucial part of material preparation at Light Bicycle. To facilitate the hand layup process in the rim mold, we execute some layup in advance on a flat surface. Lamination prepares the fabric laminates for different parts of the rim with the carbon sheets overlaid in the desired order and orientation, which allows us to manipulate the product more easily. A great example of this in practice is our innovative stepwise lamination - designed for weight saving and durability - which consists of carbon pieces overlapped with their edges recessed. This attention to detail is what proudly sets us apart from many manufacturers.

See Next Stage

Step 4: Premold and Lay-Up

To optimize mold accuracy, we design and use two-in-one molds for manufacturing. The pre-mold can go straight inside the final mold, eliminating the risk of fiber shifting during layup transfer. Before entering the layup room, the pre-mold is thoroughly cleaned and checked for scratches or damage. Then the pre-mold is heated to 40℃/50℃ (based on the rim type) to prepare it for layup.

Our layup specialist weighs the materials before the first layup, starting with sidewall construction. After applying the release agent on the mold, we carefully remove the protective paper and hand lay the fabric layers from the exterior to the interior, constructing the rim body as well as fine details like bead hook and nipple reinforcement. After each overlap, we smooth the prepregs to ensure there are no wrinkles, air bubbles, fiber fractures, or particles trapped in between the layers. When both of the layups are finished, the two parts of the premold are fixed together and prepared for the next step.

Step 5: Placing the Air Bladder

We first add carbon laminate reinforcement to the parts of the rim where spoke and valve holes will be drilled. We then insert air bladders that will shape the internal contours of the rim. We take one air bladder and place it into the concave of the premold layup with the air inlet protruding through the valve hole. The air bladder is then partially inflated to provide a platform for the rim bed and hook layup, where strict tolerances are required as this affects tire retention and riding safety. When the layup is finished, we cover the rim with a plastic protective film and move it to the molding room.

Step 6: Molding

We first conduct a quick inspection of the integrity of the rim bed and hook layup to ensure everything is in place from the pre-mold and then set it into the mold plate. The complete mold is then transferred to the molding machine for a one-hour high-temperature treatment (150℃), with the air bladder inflated to push the carbon rim against the mold. The resin flows over the carbon, cures, and creates a smooth and solid rim surface. We perform dynamic control of air pressure and temperature during the molding process for consistent resin curing and solid binding of the carbon layers. After the heat treatment, the mold is moved to the cooling machine to lower the mold temperature to 60℃. Our molding technician then removes the newly made rim from the mold and clears any excess resin. The raw rim weight gets measured and recorded.

Step 4: Premold and Lay-Up

To optimize mold accuracy, we design and use two-in-one molds for manufacturing. The pre-mold can go straight inside the final mold, eliminating the risk of fiber shifting during layup transfer. Before entering the layup room, the pre-mold is thoroughly cleaned and checked for scratches or damage. Then the pre-mold is heated to 40℃/50℃ (based on the rim type) to prepare it for layup.

Our layup specialist weighs the materials before the first layup, starting with sidewall construction. After applying the release agent on the mold, we carefully remove the protective paper and hand lay the fabric layers from the exterior to the interior, constructing the rim body as well as fine details like bead hook and nipple reinforcement. After each overlap, we smooth the prepregs to ensure there are no wrinkles, air bubbles, fiber fractures, or particles trapped in between the layers. When both of the layups are finished, the two parts of the premold are fixed together and prepared for the next step.

Step 5: Placing the Air Bladder

We first add carbon laminate reinforcement to the parts of the rim where spoke and valve holes will be drilled. We then insert air bladders that will shape the internal contours of the rim. We take one air bladder and place it into the concave of the premold layup with the air inlet protruding through the valve hole. The air bladder is then partially inflated to provide a platform for the rim bed and hook layup, where strict tolerances are required as this affects tire retention and riding safety. When the layup is finished, we cover the rim with a plastic protective film and move it to the molding room.

Step 6: Molding

We first conduct a quick inspection of the integrity of the rim bed and hook layup to ensure everything is in place from the pre-mold and then set it into the mold plate. The complete mold is then transferred to the molding machine for a one-hour high-temperature treatment (150℃), with the air bladder inflated to push the carbon rim against the mold. The resin flows over the carbon, cures, and creates a smooth and solid rim surface. We perform dynamic control of air pressure and temperature during the molding process for consistent resin curing and solid binding of the carbon layers. After the heat treatment, the mold is moved to the cooling machine to lower the mold temperature to 60℃. Our molding technician then removes the newly made rim from the mold and clears any excess resin. The raw rim weight gets measured and recorded.

See Next Stage

Step 7: Hole Drilling

After a quick inspection, the rim is delivered to the drilling room. We use aviation-grade CNC drills with drill bits specifically designed for drilling through advanced composites. The bits have a unique cutting edge which makes extremely clean holes.

Step 8: Cosmetic Treatment

Rims featuring Light Bicycle BlackTek technology require no coating as this results in a perfect finish right out of the mold. Traditional rims are sent to the painting room for a glossy, matte, or any custom finish. Waterslide decals are also applied to the rim at this point in the process.

Step 9: Final QC

We conduct a comprehensive quality inspection of all rims, first to ensure they fall within our weight tolerances. We then test more acutely for construction and performance: lateral and radial run-outs, stiffness, impact resistance, and tire inflation. Lastly, we check for any cosmetic concerns with the finish, decal, edge smoothness, parting line, or hole drilling. The rim is now complete and ready for wheel building or shipping.

Step 7: Hole Drilling

After a quick inspection, the rim is delivered to the drilling room. We use aviation-grade CNC drills with drill bits specifically designed for drilling through advanced composites. The bits have a unique cutting edge which makes extremely clean holes.

Step 8: Cosmetic Treatment

Rims featuring Light Bicycle BlackTek technology require no coating as this results in a perfect finish right out of the mold. Traditional rims are sent to the painting room for a glossy, matte, or any custom finish. Waterslide decals are also applied to the rim at this point in the process.

Step 9: Final QC

We conduct a comprehensive quality inspection of all rims, first to ensure they fall within our weight tolerances. We then test more acutely for construction and performance: lateral and radial run-outs, stiffness, impact resistance, and tire inflation. Lastly, we check for any cosmetic concerns with the finish, decal, edge smoothness, parting line, or hole drilling. The rim is now complete and ready for wheel building or shipping.

Manufacturing Process: How a Carbon Rim Is Made

Stage 1 - Material Preparation

Stage 2 - Fabrication

Stage 3 - Post-Production

Step 1: Sourcing Raw Materials

Step 2: Cutting to Size

Step 3: Lamination

Step 1: Sourcing Raw Materials

Step 2: Cutting to Size

Step 3: Lamination

Step 4: Premold and Lay-Up

Step 5: Placing the Air Bladder

Step 6: Molding

Step 4: Premold and Lay-Up

Step 5: Placing the Air Bladder

Step 6: Molding

Step 7: Hole Drilling

Step 8: Cosmetic Treatment

Step 9: Final QC

Step 7: Hole Drilling

Step 8: Cosmetic Treatment

Step 9: Final QC

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