<i>(Looking for feedback and related experiences on the following subject. It's just one guy's opinion based on a little research and a little work experience. I'm curious to see what other folks have learned about these products and how they like to employ them.)</i>
Sapim's CX-Ray spoke model has become increasingly popular in the U.S.A. Manufactured in Belgium, it is used by many of the top professional cycling teams. In fact, their list of Pro teams looks like a "who's who" of cycling. The CX-Ray begins life as a double-butted 2.0-1.5-2.0mm round Sapim Lazer spoke. The narrow 1.5mm center section is then forged (flattened) into a "bladed" (oval) shape. The black CX-Ray spokes are then finished with a premium black chromate process, as opposed to the less expensive black oxide process used by DT Swiss and Wheelsmith.
This ovalized shape allegedly gives the spokes a small advantage in terms of reducing aerodynamic drag. This aero advantage must be pretty small, and some manufacturers claim it is non-existant. For example, Lew Composites selected round spokes for their wheels, because they found wind-tunnel testing did not justify claims of enhanced aerodynamics from using bladed spokes. I'm not sure which bladed spoke models they were studying though. We can conclude that any really significant "aero" advantage for these spokes is debatable.
The obvious, measurable advantage to a forged spoke like the CX-Ray is that the forging process aligns the grain structure in the material, enhancing it's tensile strength. Simply put, it's becomes "stronger" as a result of being forged. It can accept more tension load before breaking or plastically deforming (stretching out) than the round spoke it was made from.
This allows the builder to use an extremely light spoke and still get tension levels comparable to thicker spokes. You can apply the same tension levels you'd normally use on a "14/15 gauge" spoke and have the "14/17 gauge" CX-Ray still be reliable. So they offer a nice strength advantage that can be particularly helpful when building wheels with a reduced spoke count. It's normally not too hard to acheive adequate tension on a 32 spoke wheel, regardless of the spoke selected. When working with wheels that have very few spokes though, you need every bit of tension you can get!
It's important to note that the forging process does not significantly alter the stiffness of the material used in these spokes. Sometimes you see claims that the CX-Rays are a lot stiffer than other spokes, either due to the forged material or their shape. I haven't seen any actual data to back this claim up, and the manufacturer makes no such claims about them. What may be leading to claims of enhanced stiffness is the higher tension level these spokes can offer. When a wheel is momentarily overloaded by a series of stutter-bumps or pothole impact, the spokes can lose tension and go floppy-slack. Having more tension makes this less likely.
So the CX-Ray offers a spoke this is stronger than round spokes of it's weight, and the black ones are also prettier than the DT or Wheelsmith equivalent. The downside is, of course, price. In the case of the CX-Ray, that's a pretty serious downside. Thanks in part to the lousy exchange rate with the Euro, the CX-Ray costs about 400% more than the similar AE15 model from Wheelsmith. Comparing current manufacturer cost for these spokes in quantity, the CX-Rays would add about $70 to the parts cost of a typical wheelset.
Aside from the cost of the spokes themselves, thin bladed spokes are generally more time consuming to build. Their shape allows them to twist easily, so you have to hold the spoke to keep it from twisting while turning the spoke wrench. Special tools are available for this, but the home mechanic can just use padded pliers. For manufacturers that use robotic lacers and truing machines, the CX-Ray may have to be hand-built. This helps explain why some companies must charge an extra $100 or more for building with CX-Rays.
Is this "sticker shock" pricing the only way to get this type of performance advantage? Maybe, but there are some pretty competitive alternatives available for 2004.
Wheelsmith's AE15 spoke has been around for quite a while. This starts out as a "DB15" model 1.8-1.55-1.8mm double-butted spoke. It is rolled flat in the center section into an oval "blade" shape. Weight for this spoke is almost identical to the CX-Ray. It's primary difference is the 1.8mm end sections. The smaller end sections are not as strong as the 2.0mm ends on the CX-Rays. In addition, they don't fit as snugly into the hub's spoke holes.
This fit issue is not a severe drawback when building with high-end quality hubs. These hubs will typically have 2.4mm spoke holes, whereas average hubs use a 2.6mm hole. So a 1.8mm spoke in a 2.4mm hole has the same 0.6mm "standard" clearance the industry uses on the vast majority of wheels. It's not as nice as precise as a 0.4mm clearance, but it's not exactly a major deficiency.
The strength of the 1.8mm threaded end of the AE15 spoke is about 30% weaker than a 2.0mm spoke end. That appears to be a disadvantage, but in this case appearances can be deceiving. The reason is that most of these ultra-light spokes get built up with aluminum alloy nipple. Using a 15 gauge (1.8mm) spoke means they only have to punch a 1.8mm hole in the nipple to thread it, leaving more material in the nipple wall. The aluminum nipple is the "weakest link" in terms of fatigue life. By trading off some strength in the spoke end, you are able to increase the thickness of the nipple wall and enhance the fatigue life of the component that is otherwise most likely to fail. DT Swiss's "SuperComp" model spoke, which was specifically optimized for MTB disc-brake applications with aluminum nipples, uses this same principal.
The strength of the 1.8mm head-end of the AE15 spoke is also 30% weaker than a 2.0mm head. So I prefer to use the AE15s only on front wheels and the non-drive side of rear wheels. The drive-side of the rear wheel recieves the vast majority of the pedaling torque, and is subject to constantly changing tension levels as a result. That's why I prefer to use the AE15s only on the front and non-drive rear. Our experience has been that the WS AE15 is at least as reliable as the CX-Ray when positioned in this way and built with aluminum spoke nipples.
That leaves you with 3/4ths of a wheelset. You can obviously use the CX-Rays on the drive side rear, but it's not ideal from a cost standpoint. You can also use a standard round 14/15 spoke in that position. That works very reliably, but it's not as light or as cosmetically appealing as having a matching bladed spoke.
Fortunately, Wheelsmith has introduced a bladed version of their DB14/15 spoke for 2004, the "XE14" model. These are expensive, but only about 2/3rd the cost of the CX-Rays. They are also stiffer than the CX-Rays, giving a crisper feel under hard pedalling efforts. Weight-wise, you pay for that stiffness with about 5 extra grams for the drive side of a 32 spoke wheel versus CX-Rays. For wheels with fewer spokes, the weight difference is even less. I personally like to do the drive-side of the rear wheel with brass nipples. This is the side where you are most likely to have breakage of aluminum nipples. Comboing the brass 14 gauge nips on the drive side with aluminum 15 gauge nips everywhere else gets you a very reliable fatigue life and only adds 10g on a 32 spoke wheelset compared to using all aluminum.
So, for about 15g in extra weight compared to using all CX-Rays and all aluminum nips, you can do a build using the AE15/XE15s with brass nips on the drive side. This will give you a slightly stiffer wheel that will have nipple life-span. Given the substantial difference in the price, that may be a pretty appealing alternative for U.S. buyers. Note that these WS spokes only come in silver, so you gotta go with the 'Rays if you want black.
Sapim's CX-Ray spoke model has become increasingly popular in the U.S.A. Manufactured in Belgium, it is used by many of the top professional cycling teams. In fact, their list of Pro teams looks like a "who's who" of cycling. The CX-Ray begins life as a double-butted 2.0-1.5-2.0mm round Sapim Lazer spoke. The narrow 1.5mm center section is then forged (flattened) into a "bladed" (oval) shape. The black CX-Ray spokes are then finished with a premium black chromate process, as opposed to the less expensive black oxide process used by DT Swiss and Wheelsmith.
This ovalized shape allegedly gives the spokes a small advantage in terms of reducing aerodynamic drag. This aero advantage must be pretty small, and some manufacturers claim it is non-existant. For example, Lew Composites selected round spokes for their wheels, because they found wind-tunnel testing did not justify claims of enhanced aerodynamics from using bladed spokes. I'm not sure which bladed spoke models they were studying though. We can conclude that any really significant "aero" advantage for these spokes is debatable.
The obvious, measurable advantage to a forged spoke like the CX-Ray is that the forging process aligns the grain structure in the material, enhancing it's tensile strength. Simply put, it's becomes "stronger" as a result of being forged. It can accept more tension load before breaking or plastically deforming (stretching out) than the round spoke it was made from.
This allows the builder to use an extremely light spoke and still get tension levels comparable to thicker spokes. You can apply the same tension levels you'd normally use on a "14/15 gauge" spoke and have the "14/17 gauge" CX-Ray still be reliable. So they offer a nice strength advantage that can be particularly helpful when building wheels with a reduced spoke count. It's normally not too hard to acheive adequate tension on a 32 spoke wheel, regardless of the spoke selected. When working with wheels that have very few spokes though, you need every bit of tension you can get!
It's important to note that the forging process does not significantly alter the stiffness of the material used in these spokes. Sometimes you see claims that the CX-Rays are a lot stiffer than other spokes, either due to the forged material or their shape. I haven't seen any actual data to back this claim up, and the manufacturer makes no such claims about them. What may be leading to claims of enhanced stiffness is the higher tension level these spokes can offer. When a wheel is momentarily overloaded by a series of stutter-bumps or pothole impact, the spokes can lose tension and go floppy-slack. Having more tension makes this less likely.
So the CX-Ray offers a spoke this is stronger than round spokes of it's weight, and the black ones are also prettier than the DT or Wheelsmith equivalent. The downside is, of course, price. In the case of the CX-Ray, that's a pretty serious downside. Thanks in part to the lousy exchange rate with the Euro, the CX-Ray costs about 400% more than the similar AE15 model from Wheelsmith. Comparing current manufacturer cost for these spokes in quantity, the CX-Rays would add about $70 to the parts cost of a typical wheelset.
Aside from the cost of the spokes themselves, thin bladed spokes are generally more time consuming to build. Their shape allows them to twist easily, so you have to hold the spoke to keep it from twisting while turning the spoke wrench. Special tools are available for this, but the home mechanic can just use padded pliers. For manufacturers that use robotic lacers and truing machines, the CX-Ray may have to be hand-built. This helps explain why some companies must charge an extra $100 or more for building with CX-Rays.
Is this "sticker shock" pricing the only way to get this type of performance advantage? Maybe, but there are some pretty competitive alternatives available for 2004.
Wheelsmith's AE15 spoke has been around for quite a while. This starts out as a "DB15" model 1.8-1.55-1.8mm double-butted spoke. It is rolled flat in the center section into an oval "blade" shape. Weight for this spoke is almost identical to the CX-Ray. It's primary difference is the 1.8mm end sections. The smaller end sections are not as strong as the 2.0mm ends on the CX-Rays. In addition, they don't fit as snugly into the hub's spoke holes.
This fit issue is not a severe drawback when building with high-end quality hubs. These hubs will typically have 2.4mm spoke holes, whereas average hubs use a 2.6mm hole. So a 1.8mm spoke in a 2.4mm hole has the same 0.6mm "standard" clearance the industry uses on the vast majority of wheels. It's not as nice as precise as a 0.4mm clearance, but it's not exactly a major deficiency.
The strength of the 1.8mm threaded end of the AE15 spoke is about 30% weaker than a 2.0mm spoke end. That appears to be a disadvantage, but in this case appearances can be deceiving. The reason is that most of these ultra-light spokes get built up with aluminum alloy nipple. Using a 15 gauge (1.8mm) spoke means they only have to punch a 1.8mm hole in the nipple to thread it, leaving more material in the nipple wall. The aluminum nipple is the "weakest link" in terms of fatigue life. By trading off some strength in the spoke end, you are able to increase the thickness of the nipple wall and enhance the fatigue life of the component that is otherwise most likely to fail. DT Swiss's "SuperComp" model spoke, which was specifically optimized for MTB disc-brake applications with aluminum nipples, uses this same principal.
The strength of the 1.8mm head-end of the AE15 spoke is also 30% weaker than a 2.0mm head. So I prefer to use the AE15s only on front wheels and the non-drive side of rear wheels. The drive-side of the rear wheel recieves the vast majority of the pedaling torque, and is subject to constantly changing tension levels as a result. That's why I prefer to use the AE15s only on the front and non-drive rear. Our experience has been that the WS AE15 is at least as reliable as the CX-Ray when positioned in this way and built with aluminum spoke nipples.
That leaves you with 3/4ths of a wheelset. You can obviously use the CX-Rays on the drive side rear, but it's not ideal from a cost standpoint. You can also use a standard round 14/15 spoke in that position. That works very reliably, but it's not as light or as cosmetically appealing as having a matching bladed spoke.
Fortunately, Wheelsmith has introduced a bladed version of their DB14/15 spoke for 2004, the "XE14" model. These are expensive, but only about 2/3rd the cost of the CX-Rays. They are also stiffer than the CX-Rays, giving a crisper feel under hard pedalling efforts. Weight-wise, you pay for that stiffness with about 5 extra grams for the drive side of a 32 spoke wheel versus CX-Rays. For wheels with fewer spokes, the weight difference is even less. I personally like to do the drive-side of the rear wheel with brass nipples. This is the side where you are most likely to have breakage of aluminum nipples. Comboing the brass 14 gauge nips on the drive side with aluminum 15 gauge nips everywhere else gets you a very reliable fatigue life and only adds 10g on a 32 spoke wheelset compared to using all aluminum.
So, for about 15g in extra weight compared to using all CX-Rays and all aluminum nips, you can do a build using the AE15/XE15s with brass nips on the drive side. This will give you a slightly stiffer wheel that will have nipple life-span. Given the substantial difference in the price, that may be a pretty appealing alternative for U.S. buyers. Note that these WS spokes only come in silver, so you gotta go with the 'Rays if you want black.
