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  1. #1
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    Thoughts on Sapim CX-Ray vs. WS AE15/XE14

    (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.)

    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.
    Last edited by bianchi4me; 03-23-2004 at 08:18 AM.

  2. #2
    Cipo's long lost cousin
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    A few notes on AE15's

    Hey Mike,

    The wheels I built up over the winter with AE15's have worked out pretty well.

    As for physical appearance, the flat section of AE15's are barely noticible when compared to CX-Rays. Most people who see these wheels never even realize that they are bladed spokes. With the DT Swiss Hugi 240 hubs the spoke head sits nearly flush with the hub flange. This provides a very clean look to the finished product. Personally, I hate it when I see spoke heads sitting unevenly in the spoke hole due to to a mismatch in diameters.

    The AE15's are a little tricky to build. They do "twist" much more then conventional spokes during tensioning. The nice part is that the ovalized section of spoke allows you to see the wind up of the spoke and correct it as you build. I don't use a tensiometer on my builds but go by feel and "plucking" the spokes. I put normal tension on the AE15's and haven't noticed any flexing of the wheel or brake rub in hard corning.

    I have 500 miles on these wheels with a 2x pattern in the front (AE15's) and a 2x/3x pattern in the rear (AE15's/DB14's) with no issues. The rims are Velocity Aerohead (28h Front) and Fusion (32h Rear). I go 195 lbs. so I'm no lightweight and the AE15's have worked nicely... While I'd like to try CX-Rays they are a little spendy for me...



    "Cycling is like a church - many attend, but few understand." -- Jim Burlant

  3. #3
    Cipo's long lost cousin
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    Bladed vs. Round

    From Zipp's website....



    Of course the text on the page this graphic is linked from provides no technical info. They also don't take on the issue of crosswind affects on bladed vs. round spokes. Probably too much wind tunnel $$ justify the little affect it actually has on the rider...

    Now these ceramic bearings certainly look tempting!
    "Cycling is like a church - many attend, but few understand." -- Jim Burlant

  4. #4
    all the gear - no idea
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    Question barnett's manual chapter

    Great looking wheels Steve

    I am trying to psyche myself up to build my first pair (aeroheads on centaur hubs with sapim race spokes) - where can I get the Barnett chapter on wheel building? I have the zinn book and sheldon's great info too, plus the link you mentioned on mtbr.

    Thanks for any help. (your pictures were the encouragement I need!)

  5. #5
    Cipo's long lost cousin
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    Quote Originally Posted by charlieboy
    Great looking wheels Steve

    I am trying to psyche myself up to build my first pair (aeroheads on centaur hubs with sapim race spokes) - where can I get the Barnett chapter on wheel building? I have the zinn book and sheldon's great info too, plus the link you mentioned on mtbr.

    Thanks for any help. (your pictures were the encouragement I need!)

    Here you go!

    http://utagawa.free.fr/VTT/Tech/Barn...eplacement.pdf

    Take some picts and let us know how it goes!
    "Cycling is like a church - many attend, but few understand." -- Jim Burlant

  6. #6
    all the gear - no idea
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    Smile thanks steve

    Quote Originally Posted by Steve-O
    Here you go!


    Take some picts and let us know how it goes!
    Thanks for that Steve - my project is slowed by fear (of failure!) and a tight budget, but I will keep rbr posted. Now I have all the destructions necessary there is no real excuse...

  7. #7
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    Don't forget the venerable DT Revolution spokes as an option as well. They come in black as well. I have had good luck with them in the past.

    My Rolf Prima Elan Aero's came with the Sapim CX-Rays. They are definitely nice looking, but sharp. Bet I could ginzu anything dumb enough to run into my wheels.

    I am curious about the aero effect of the fat bladed aero spokes on the Mavic K' SSC SL's. Straight line they seem faster, but side winds effect them more (in my observations to date as least). My new bike came with them, and I left them on to get some experience with them.
    Dr. Cox: Lady, people aren't chocolates. Do you know what they are mostly? Bastards. Bastard-coated bastards with bastard fillings. But I don't find them half as annoying as I find naive bubble-headed optimists who walk around vomiting sunshine.

  8. #8
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    Assuming deflection is a good measure of stiffness, the tensionmeter charts I have all indicate the CX-rays are stiffer than the rest, including the XE14's.

    I really don't like the AE-15 spokes - in my experience they aren't aero at all (very noisy at speed - something with the shape/consistency of the edges I think), and suck to build with due to the wind up problems. My favorite traditional oval spokes were the ones Performance used to sell in the 80's, no idea who made them but they were very smooth, quiet and noticeably faster than the Wheelsmith ones.

    The CX-rays are ridiculously expensive, and were even when the euro was at $0.83 instead of $1.23, but after rebuilding a few WS/DT wheels with them there is no way I am going back. I like the black too, especially with gold nips and carbon rims.

  9. #9
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    Charts don't appear to agree.

    That's interesting that your chart is giving you a different result. The one that accompanies the Park tensiometer shows the CX-Ray having more deflection than the AE15. I confirmed with Park that the CX-Ray reading should be taken using the "2.1x1.0"mm column on their tensiometer. This shows that it has more deflection than the AE15 which is listed on their chart at "2.2x1.3". I asked the Park Tools rep about these dimensions, since they vary slightly from the published specs for these spokes. He explained that these are based on their actual measurements of the spokes, as opposed to the company's claimed specs.

    I'm curious which tensiometer chart you're using? I've got the Wheelsmith, Park Tools, and DT Swiss Analog tensiometers on hand. None of these have a value listed that exactly matches the CX-Ray's published dimensions. None of them have a value that exactly matches the center dimensions on the XE14 either, that one just came out this year. So I'm wondering what tensiometer chart you are using to compare the stiffness of these spokes? It would be nice to have a "model specific" chart like that.

  10. #10
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    Quote Originally Posted by bianchi4me
    That's interesting that your chart is giving you a different result. The one that accompanies the Park tensiometer shows the CX-Ray having more deflection than the AE15. I confirmed with Park that the CX-Ray reading should be taken using the "2.1x1.0"mm column on their tensiometer. This shows that it has more deflection than the AE15 which is listed on their chart at "2.2x1.3". I asked the Park Tools rep about these dimensions, since they vary slightly from the published specs for these spokes. He explained that these are based on their actual measurements of the spokes, as opposed to the company's claimed specs.

    I'm curious which tensiometer chart you're using? I've got the Wheelsmith, Park Tools, and DT Swiss Analog tensiometers on hand. None of these have a value listed that exactly matches the CX-Ray's published dimensions. None of them have a value that exactly matches the center dimensions on the XE14 either, that one just came out this year. So I'm wondering what tensiometer chart you are using to compare the stiffness of these spokes? It would be nice to have a "model specific" chart like that.
    Now that you jog my memory I realize that none of them have a specific listing for the CX. I measured the deflection myself and used the columns that were closest to what I measured. I had been told by one of the manufacturers (can't remember which one) to use whatever had the closest dimensions but that wasn't close to what it was in reality.

    The easiest way to get a good estimate is to replace a few spokes in a front wheel built with a known spoke to specific tension and measure the values on the replaced spokes after the wheel is retrued.

  11. #11
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    Sent some XE14s in for evaluation.

    That sounds good. Your "next closest" value is probably about as good as we are going to get to a "real" value anyway. I suspect the dimensions on these spokes change slightly from batch to batch, like most parts do. So it's probably impossible to nail down an truly exact readout for a model.

    I sent a couple of the XE14s into Park Tool today for them to measure dimensions and come up with a recommended tensiometer reading. Hopefully we'll have some info about that in a few days. I just wonder how closely that spoke is going to fit into an existing category on thier chart. Hopefully the "next closest" existing value will be pretty close to the actual specs on the XE14!

  12. #12
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    Hey Steve...

    Thanks for the feedback and the chart, that's nice info. Build looks nice too.

    The guys at Lew said that when you compare the bladed spokes with a strictly 100% headwind, they do of course win out. So of course that's the only direction you ever see test results from spoke and wheel makers, ala the Zipp chart.


    But Lew found that when you move the wind direction off of dead-center, even by a few degrees, the drag numbers for bladed spokes shoot up rapidly. The farther off-center the wind direction gets, the higher the drag for the bladed spokes versus round spokes, until you reach a point where they are actually less efficient. So any kind of half-way serious crosswind really messes up the efficiency of the bladed shape. They decided to spec 1.5mm round spokes on their wheels as a result.

    I'm not sure I agree with them, because when you are cycling you are making your own headwind. Obviously headwind is going to be the prevailing condition most of the time. So I would therefore expect the blade to be at least a little better most of the time. I don't know which bladed spokes Lew was looking at... If if was a big, heavy, 14g blade, then obviously they were also looking at a big weight penalty for using bladed spokes. With the newer butted bladed spokes like the AE15s and CX-Rays, there isn't any weight penalty at all versus round 1.5mm spokes like the Revo/Lazer/XL14 models.

    Lew's results indicate that the "best" spoke aerodynamically really depends on which way the wind is blowing! I guess if you live in an area prone to fierce cross-winds, that might be someting to think about....

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