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AASQ Nº 130: Gravel Wheel Technology Explained with Hunt, Scope, Reserve, and Fulcrum


We know, there are no stupid questions. But there are some questions that you may not want to ask your local store or your cyclist friends. AASQ is our weekly series where we get to the bottom of your questions, whether they are serious or not. Click on the link at the end of the post to submit your own question. Welcome back to GravelBikes’s stupid questions series. This week we dive into gravel wheel technology, considering the advantages of symmetrical and asymmetrical rim profiles, internal spoke nipples, vibration damping, and how many spokes are too many? Joining us are the following experts: Which type of rim profile is better for gravel riding, symmetrical or asymmetrical? HUNT: It depends on a couple of variables, including the type of gravel riding you do. As we all know, gravel means many things to many cyclists. For example, the HUNT 42 Limitless Gravel Disc is designed to maximize aerodynamic performance in gravel riding, and this can only be achieved with a symmetrical rim designed to be as aerodynamically efficient as possible with 700×38/42c gravel tires. The “dirty” airflow coming off the knobby gravel tires makes gravel aerodynamics more complicated than smooth road tires; read more about the aerodynamic testing of Hunt 42 Limitless Gravel Disc wheels here. Asymmetry in the profile design focuses on maximizing durability, as it achieves an improved bracing angle. The consequence is usually a more balanced spoke tension between the drive-side and non-drive-side spokes, resulting in a reliable system for off-road adventures. ÁMBITO CICLISMO: The choice between a symmetrical or asymmetrical rim shape is not related to the terrain or environment in which the wheels are used. The main reason for using an asymmetrical rim profile is to balance the tension of the drive-side and non-drive-side spokes. At Scope, we use a 2:1 spoke ratio to balance the tension of the spokes and therefore do not need to use an asymmetrical rim shape. We always prefer a symmetrical rim shape, as it outperforms an asymmetrical rim in terms of aerodynamics. Therefore, we only use asymmetrical rims when we cannot apply a 2:1 spoke ratio and when aerodynamics does not play a significant role. For example, in the case of our R2.O all-terrain rear wheel, which has 28 spokes. More information about Scope Cycling’s three sets of carbon gravel wheels here. In general, the rim profile is important when it comes to certain riding characteristics, such as comfort and durability, which are important for gravel riding. When developing a rim shape at Scope, we conduct FEM analysis to determine the level of vibration damping of the rims. In the case of all-terrain rims, we want to achieve high scores in vibration damping, which translates into a wider and rounder rim shape. Our All Road wheel range features a 30mm wide rim (23mm internal width) that offers both comfort and excellent aerodynamic performance (low aerodynamic drag combined with great crosswind stability). RESERVE: Asymmetrical rims are very effective in balancing spoke tension and length to match the asymmetry of the hubs. This results in stiffer, stronger, and more reliable wheels, which are exactly the attributes you look for in a gravel wheel. In addition to asymmetry, we (Reserve) also design the profile and material thickness to provide a specific ride quality for the intended category. FULCRUM: At Fulcrum, we believe that an asymmetrical rim solution is preferable for gravel, as it ensures a perfect balance in spoke tension, with the possibility of reducing spoke tensions, which in turn can help the wheels better follow the terrain. This means better control and a more forgiving and comfortable riding feel. Check out Cory’s review of the Fulcrum Rapid Red 3 Alloy Gravel wheelset here. Do you use internal spoke nipples? Do they work with asymmetrical rims? HUNT: Yes, asymmetrical rims make it difficult to use internal spoke nipples, mainly because of the access from the tire bed to the nipple. This is because the hole in the tire bed has limited size and location. In low-profile rims, other issues arise due to the proximity of the internal nipple to the displaced side’s sidewall. Check out the carbon laminated spokes (with external nipples) from the prototype Hunt Proven XC wheelset we saw on Isla Short’s Orbea Oiz World Cup race bike. It is plausible to do so in cases of slight asymmetrical offset or deeper rims specifically designed for it; however, this negatively affects ease of use and may not align with the advantages of designing asymmetrically (to the point that we do not design any of our rims or wheels, whether they are asymmetric or not, with internal spoke nipples). ÁMBITO CICLISMO: Internal spoke nipples can be combined with off-center spoke drilling. At Scope, we do not use off-center drillings (for the same reason we do not use asymmetrical rims) or internal spoke nipples for maintenance reasons. RESERVE: Internal spoke nipples can be used with offset designs, but we do not recommend internal designs. Rims designed to be built with internal spoke nipples will have smaller spoke holes to increase contact area with the nipples, so all Reserve wheels are built with external nipples, which we have found to be easier to build and maintain, provide a better overall wheel structure, and have a measured insignificant impact on aerodynamic drag. FULCRUM: We (only) use external spoke nipples because it makes everything easier for maintenance. In our high-end carbon and alloy models, we use our patented MoMag technology, where the nipples, once inserted inside the rim through the valve hole, are “guided” to the connection point with the spoke by the magnet. This simple but ingenious system allows for wheels/rims without holes in the upper bridge to make the wheels tubeless without the need for cumbersome tubeless tape. Are gravel wheels designed to provide more vibration damping than MTB wheels, given the smaller volume of the tires and the lack of suspension? HUNT: It is difficult to compare, among other things because the performance needs of gravel and MTB wheels are quite different. MTB wheels typically have a very shallow profile, which certainly is one of the easiest ways to increase vertical compliance, but gravel riders are increasingly looking for aerodynamics to improve their speed, so it’s not as straightforward. There are several ways to design our gravel wheels to improve vibration damping. Some of them focus on the rim, whether it’s low-profile designs to add compliance, material selection, or laminate optimization (in the case of carbon), but of course also on other components like spoke gauge and count. This is very similar to what happens in any discipline, but it’s the understanding of the specific needs of gravel riders across a wide range of use cases that allows us to offer comfortable wheels without compromising other…

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