So what’s the deal with those internal nipples? This is a question we hear from our customers on a regular basis. To explain ENVE’s use of internal nipples, it is first important to understand how we arrived at the decision to produce rims that utilize internal spoke nipples.
Since day one, our goal at ENVE has been to create a better ride experience and our primary method of delivering on that promise is by building the best carbon rims on the planet. By our definition the best carbon rim is purpose built for a specific application and is therefore optimally strong, light, stiff, and reliable. However, we don’t stop there, a rim must be built into a wheel, and ultimately the ride and ownership experience you have with any complete wheelset is only as good as the quality of your wheelbuild.
When the engineering team looked at employing a traditional wheelbuild with a carbon rim, pain points were quickly identified in the user experience in the form of prematurely fatigued and broken spokes, impossible to keep true wheels, and challenging serviceability. Solving these problems has been and continues to be a first priority for our engineering team. Truing a wheel or replacing the occasional broken spoke after years of hard riding and abuse is par for the course – doing so on a regular basis was and is unacceptable.
By employing our extensive knowledge of carbon fiber, we were able to identify several ways to improve rim performance and the quality of the wheelbuild itself. First was simply designing the rim to play to the inherent strength of carbon fibers. Carbon is famous for its incredible tensile strength, or said another way, its ability to support a load under tension.
So what does this have to do with building a carbon rim into a wheel? When we design any new rim or product, we aim to maximize the number of continuous uninterrupted carbon fibers in the product. This isn’t the cheapest or easiest way to manufacture a carbon product, but in the case of rims and components, it’s the best way. Other rim manufactures drill the spoke and valve holes in the rim which if left without reinforcement, will compromise the strength and integrity of the rim itself because the strong carbon fibers have now been cut in the drilling process. The solution, is to reinforce these compromised areas with more fibers to make them strong enough to carry the load from the spoke tension. This process also adds unnecessary thickness and weight to the rim’s structure.
Our solution was the Molded Spoke Hole, a patented ENVE technology that leaves the fibers uncut by molding the spoke and valve stem holes into the rim versus drilling them.
By employing this technology, ENVE rims are lighter weight without sacrificing durability and stiffness. The outstanding strength and lightweight of ENVE rims can in part be attributed to the decision to employ internal nipples. The molded spoke hole can be smaller requiring less material reinforcements. Additionally, a smaller spoke hole is stronger than a larger hole.
As mentioned earlier, broken spokes have historically plagued carbon rims. The reason why can often be attributed to the reinforcements required to strengthen the rim as a result of drilling the internal or external nipple spoke holes. The reinforcements thicken the spoke face of the rim and inhibit the spoke nipple’s ability to articulate. When this happens, the spoke will be point loaded against the carbon rim or end of external nipple and bent. The bending stress combined with the tensile stress will cause premature fatigue and failure. In some cases manufacturers will add a washer to allow the nipple to articulate, but this adds thickness to the spoke face, creates a challenging wheelbuild, and adds more weight and complexity to the wheel system.
The ENVE Molded Spoke Hole solves these problems as well. The backside of the molded in spoke hole features a conical nipple seat that allows the nipple to articulate like a ball in socket joint. The thin spoke face of an ENVE rim paired with the molded in internal nipple seat allows the spoke to exit the rim at the same angle that the nipple is seated at. This simple adjustment in the spokes exit geometry reduces stress on the spoke and guarantees that your wheel will require less (if any) truing and greatly reduces the likelihood of fatigue induced broken spokes.
So back to the original question, why the internal nipples? Simply, when paired with our patented Molded Spoke Holes, they produce a more durable and reliable wheelbuild. Consider these concepts upon your next wheel purchase, and remember that a purposeful spoke hole design and wheelbuild will lead to an enhanced ownership and ride experience.