The Carbon Rim Production Process at NTP Composites
At NTP Composites, we take immense pride in the quality and precision that goes into every carbon bike rim we manufacture. You may have caught Trace Velo's fantastic video showcasing the process, but in this article, we're diving a bit deeper—offering an insider's look at the meticulous steps and technical expertise that ensure our rims are second to none. Here's a behind-the-scenes tour of our carbon rim manufacturing process:
Every great product starts with exceptional materials, and that’s exactly what we use at NTP. We work with top-tier thermoset carbon prepregs—carbon fibers pre-impregnated with resin that cures under heat. These prepregs are delicate, so we store them in a climate-controlled refrigerator to protect them from dust, heat, and moisture. The prepregs are stored wrapped in an outer film, and our production manager plans ahead, pulling the required amount of rolls a day before production. After being removed from cold storage, the prepregs thaw at room temperature for 24 hours to ensure they’re ready for use. Once thawed, we use them within 48 hours to maintain optimal quality.
While the outer layer of our rims might showcase different weaves, the core is primarily made from uni-directional (UD) carbon for strength and consistency. Each UD prepreg, sandwiched between a protective plastic film and release paper, is cut at precise angles (0°, 30°, 45°, 60°, 90°) and sliced to the required widths and lengths. These specifications vary based on the design of the rim and customer requirements.
The lamination process is carefully done on a flat table or plate, ensuring precise layering of the carbon prepregs before they are transferred to the premold. Technicians layer the carbon prepregs in specific patterns, according to the rim design, paying special attention to the precise placement of the center channel. We also prepare key components like hole reinforcement pads and carbon rods. The hole reinforcement pads are small, laminated carbon rectangles designed to strengthen areas weakened by hole drilling. Carbon rods, hand-rolled with tapered ends, are essential for the rim's curvature and bead hook formation.
Once the lamination process is complete, the materials are carefully stored in water-resistant bags, and we follow the "first-in, first-out" rule to maintain material freshness.
Before the layup process begins, a technician gathers all the materials required to make one complete rim. The total weight of these materials is carefully recorded in our order management system to ensure consistency and precision. The materials for one rim—comprising carbon laminates for sidewalls and rim bed, carbon rods, air bags, and hole reinforcement pads—are grouped together in one waterproof bag and tagged with a serial number. This allows us to maintain strict control and traceability throughout production.
At this point, our technicians prepare the alloy premold that matches the specific rim model. The layup process begins from the outer layer of the rim, working inward toward the inner rim bed. Technicians start with the sidewalls, then move on to the hole reinforcement around the inner circumference. Next, the air bag is carefully inserted and wrapped, followed by the carbon laminates for the rim bed and the carbon rods, which secure the rim’s curvature and bead interface.
Throughout the layup, we conduct regular self-inspections to ensure there are no imperfections like dust, wrinkles, or misalignments that could weaken the final product. Once the layup is complete, a silicone strip is applied to the rim bed to set its shape.
Before moving to the next stage, the layup is weighed again to ensure it matches the target specifications, with any discrepancies flagged in the order management system.
Now, it's time for the hot press curing. Before placing the premold layup into the mold, our technicians clean the mold surfaces thoroughly to remove any residue. A layer of ultra-thin fabric is applied to ensure smooth demolding after curing.
Once the layup is carefully sealed into the mold, the air bag is inflated to around 160 psi, applying pressure from the inside. The curing process lasts between 45 minutes to an hour depending on product types, during which the mold is heated to ensure the resin sets perfectly.
Once the curing is complete, the mold is transferred to a cooling facility where the rim mold cools down to 45°C. At this stage, the rim is removed from the mold and weighed again for quality assurance.
With the air bag removed, the rim is ready for hole drilling. Each rim is customized according to the client’s specifications, whether it’s hole count, nipple type, or lacing pattern. We use high-precision aviation-grade drill bits, and to maintain quality, drill bits are regularly replaced.
After drilling, the technician deburrs the holes and conducts a thorough inspection. For road rims, 100% of the rims are tested for tire retention at high pressures—at 150 psi, the rim flatness must remain within 0.3mm.
Next, the rim goes through fine post-treatment, including surface abrasion for optimal roughness, making it ready for decals and coatings. We partner with a trusted painting facility to ensure the final finish is smooth and durable.
Once the rims are returned, they undergo a final round of quality checks. Our QC team inspects weight, appearance, hole quality, graphics, labels, roundness, and flatness to ensure every detail is perfect.
For complete wheel orders, we lace the rims to the desired lacing pattern, ensuring even spoke tension. After stress relieving, the wheels are trued and checked for run-out and dishing, ensuring they’re in perfect condition straight out of the box.
