# DIY 2:1 Lacing like campy, fulcrum



## brianvonlehe (Nov 7, 2005)

So campy likes twice as many drive side spokes as non drive side on their rear wheels. Campy branded wheels use paired spokes, fulcrum branded wheels have evenly spaced spokes. A handbuilder can easily do this 28 hole hub and rim minus half the radially-laced non drive spokes = 21 spokes, 32=24, 36 becomes 27. What do you think are the limitations? System wheels typically have heavy, wide rims, as far as i can tell. Fulcrum rims are wider than K's, according to cyclingnews.com, which must be 22 or more millimeters. How light of a rim will handle spoking like this? a 36 hole Aerohead with 27 spokes? what do you think?


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## danl1 (Jul 23, 2005)

I've been fascinated by triplet lacing lately, too. As much as I hate to say it, try a search on "triplet lacing" and you'll find some good info.

36/27 seems to be a problem, because it'd be hard to find 27 hole rims. Using a 36 hole rim but leaving 9 empty? Not sure I like that idea, though I'd be interested to see that pattern laced up.

32/24 (that is, a 32 hole hub, skipping every other NDS hole, using all 24 holes in the rim) seems more even. I'd believe it if someone told me it was stronger that way.

There have been a few examples here recently where the NDS is x1 or x2 instead of radial. Given that most rears aren't particularly designed for radial, and especially not half-radial, that might make more sense. Abundance of caution and all. Not as cool looking, though.

I don't know enough about components to claim any sort of expertise, so I'll be reading the responses here with interest.


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## ergott (Feb 26, 2006)

http://forums.roadbikereview.com/showthread.php?t=83250

I did my pair like that. The best way to do it is to use a 32 hole hub and a good, stiff 24 hole rim. 16 drive and 8 non. The problem with other combinations is finding a 21 or 27 hole rim. most rims aren't strong enough to handle skipping holes. That, or they will be very difficult to true and durability will be an issue.

-Eric


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## rruff (Feb 28, 2006)

ergott said:


> The problem with other combinations is finding a 21 or 27 hole rim. most rims aren't strong enough to handle skipping holes. That, or they will be very difficult to true and durability will be an issue.


I understand your concern, but I truly don't *think* it will be a problem to skip holes. The span of unsupported rim isn't as much as paired spoke wheels, some of which use a lighter and more flexible rim. The gap is larger than on the wheel you built, but the other spokes are a little closer together... so I wouldn't necessarily be expecting a problem with lateral "waviness", which I think is the main issue.

Have you tried lacing up one of these and skipping holes? I'm going to do a 21 hole rear with the Niobium 30 rim unless somebody tells me that it doesn't work...


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## brianvonlehe (Nov 7, 2005)

right, i didn't explain myself very well. My idea about the 21 and 27 is to skip holes, and plug them with a thin layer of marine sealant or something. If fulcrum wheels are evenly spaced, and campy are paired, i don't think there's any reason something in between the two won't work. If there is, i don't understand it and i'm happy to know. My concern is the lateral stiffness of rims. My original plan was to use the niobium 30 rims in 32 hole and lace in a 32 campy hub with 24 spokes. Recently i have been thinking about doing some low profile rims instead, since my best riding strengths are climbing and sprinting and i could save quite a bit of money on rims, and worry that a light rim like aerohead/cadence would not respond well to 2 drive side spokes next to each other, but i don't know. my reluctance to just go 28h normal is that then for campy i have to buy record hubs or expensive boutique hubs, and i would rather just use a centaur hub because they are basically the same anyways.
i may experiment: 
if school is not too busy one weekend i will detension my daytona/sun assault 32 hole rear wheel and rebuild it 24h with skipped non drive holes. If that holds up for some training, i'm sure 27 spokes on an aerohead would because those sun assault rims are super skinny and soft.

after posting my original i did run into the mention of "triplet" lacing and that guy's ac420/tune wheels, but i think you are right that radial looks cooler. when there's only half the non drive side spokes, the typical rationale for lacing nds radial (so all nd spokes are under high tension always, even during drive torque) may not apply, so maybe laced 1x or 2x makes sense.


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## brianvonlehe (Nov 7, 2005)

also does anyone know how you can get cadence aero rims through your LBS? What distributor carries them?


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## rruff (Feb 28, 2006)

brianvonlehe said:


> My concern is the lateral stiffness of rims. My original plan was to use the niobium 30 rims in 32 hole and lace in a 32 campy hub with 24 spokes.


If you look at the wheels that Eric (ergott) built recently, the AC420s lace up really nicely using a 24 hole rim and a 32 hole hub, and the Niobium 30s should be very similar. I would go that route if you are using a 32h hub.

I wasn't planning to plug the holes on my rim (28-14/7). If you are worried about water, I'm sure that more runs down the spoke and gets in through the gap between the nipple and rim than would get in through that little hole. There needs to be a drain hole in the rim somewhere if you ride in the rain. 

I can't say about using an Aerohead with this lacing. I have some 36h hubs that I'd like to use this lacing pattern on, and I'm curious about how light of a rim would work. 

I don't think you will lose anything in sprinting or climbing by going with a deeper rim, though. Aero rules... and even on a climb it needs to be quite steep before the small weight savings outweighs the aero difference. Anybody with a cheap scale can measure the weight though... but aero is more nebulous...

Going 1x on the NDS is a good idea if you are starting with a 32h hub, just because it is easy enough to do it, and if the hub isn't designed for radial lacing you might as well. I think it looks as good as radial. If you start with 36 or 28, you can't though, because you have an uneven number of spokes on the NDS.


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## danl1 (Jul 23, 2005)

I have nothing to back this up, but skipping rim holes bothers me from a strength/durability/truing standpoint. When a hole has a spoke in it, it's part of a structure and all's well. If there's nothing there as with a G3 wheel, the stresses are somewhat uneven but a stiff enough rim can handle it, especially since the laterally opposing forces are clustered. This wheel would seem to require a fair amount more radial stiffness than normal (to stay round with only 7 effective spoke points), but lateral stiffness of the rim shouldn't be a problem. 

For a Fulcrum wheel the lateral forces are somewhat more imbalanced, with two DS spokes next to each other on an evenly spaced wheel. That is, the spokes have more 'leverage' to pull the rim out of lateral trueness. This wheel would seem to require less radial stiffness in the rim than the G3, but more lateral stiffness. 

A 'skipped' rim seems to take the bad parts of each, and add an extra problem. Because of the uneven spacing, it requires some of the radial stiffness of a G3. Because of the wider spacing of opposing spokes, it would want more lateral stiffness like a Fulcrum. Then, right at the point of the rim where these extra bits of stiffness and strength are needed the most - we drill a hole. If that hole were being used to distribute some of the imbalance (with a spoke), OK. But if it's just a hole, it's in exactly the wrong place and is only causing more weakness.

This would be pretty much the same as building up a cross DS, radial NDS wheel - pretty normal stuff - then cutting out half of the NDS spokes and expecting things to work out well. That just doesn't smell right. 

Opinion only - I'd love to be wrong on this. There is the Khamsin to be considered, which except for the empty hole is close to what we're talking about. At 1895g for the set, it's tough to consider that an argument in favor.


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## Ligero (Oct 21, 2005)

I have done a 18h triplet rear both ways of using a 18h rim and 24h rim skipping every third hole. I have a picture of the completed wheel but I can't find it right now, I will try to post it later.


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## Dicky dirtrider (Dec 9, 2006)

*27 hole rim*

Fulcrum Racing 5 wheels use a 27 spoke rear rim, maybe they are available separately as a replacement part?


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## ergott (Feb 26, 2006)

rruff said:


> I understand your concern, but I truly don't *think* it will be a problem to skip holes. The span of unsupported rim isn't as much as paired spoke wheels, some of which use a lighter and more flexible rim. The gap is larger than on the wheel you built, but the other spokes are a little closer together... so I wouldn't necessarily be expecting a problem with lateral "waviness", which I think is the main issue.
> 
> Have you tried lacing up one of these and skipping holes? I'm going to do a 21 hole rear with the Niobium 30 rim unless somebody tells me that it doesn't work...


I don't think the idea of skipping holes is so bad that it shouldn't be tried. Go for it and let us know. I've been thinking about trying it with some extra parts laying around to see what I think. I have some cheap rims and hubs that I can use for experiment's sake. If I do, I'll post my results.

-Eric


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## eddie m (Jul 6, 2002)

I like the idea of skipping holes.
The holes are on the neutral axis, so they should not affect the strenght or stiffness significantly.
The lateral bending moments should be less than with even spacing, but more than with closely space triplets like Campy G3's. I think you would want a slightly wider rim for any triplet patern, but the closer the 3 opposing spokes are, the less you need to go wider.
The radial loads in a 9s wheel are carried mostly by the drive side spokes. I don't think dropping half the non-drive side spokes will have much affect on the radial strength. The longest spans will still be less than with paired spoke wheels, or even Campy G3's. In any event, a deep section aero rim should be stable enough radially in any pattern.
I also like the idea of using more spokes and lighter rims on the rear. The aero benefits are not really there on a rear wheel, so I like the greater reliabilty and/or less weight of more spokes/lighter rims.
If a needed an aero rear wheel, I'd build up a 36 spoke wheel and put a cover on it.

em


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## brianvonlehe (Nov 7, 2005)

One thing about triplet lacing is that if you lose a NDS spoke things are going to be _really_ bad.
danl1- i agree with you about the lateral stiffness of fulcrum, which is exactly why i was imagining a skip-hole to be better...a little closer to G3.
anyone know how wide a sun venus rim is? i can't read the charts on sun-ringle's website.


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## rruff (Feb 28, 2006)

danl1 said:


> A 'skipped' rim seems to take the bad parts of each, and add an extra problem. Because of the uneven spacing, it requires some of the radial stiffness of a G3. Because of the wider spacing of opposing spokes, it would want more lateral stiffness like a Fulcrum. Then, right at the point of the rim where these extra bits of stiffness and strength are needed the most - we drill a hole.


Or you could say it has *less* of the bad parts of either... and that extra hole is not a problem. The stress should be less than if a spoke was attached. Getting rid of material between the spoke attachment points is a good way to optimize the strength/weight of the rim.


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## rruff (Feb 28, 2006)

brianvonlehe said:


> anyone know how wide a sun venus rim is? i can't read the charts on sun-ringle's website.


I don't know of any suitable rim that is more than 20mm wide. The Niobium 30s are <19mm wide. Personally, I like the idea of deeper rims being 21-22mm wide to make a better aero transition with a 23mm tire... but they don't seem to make them like that. 

If you want high stiffness you could use a Deep V. I tnink the Niobium 30 would be better than a Venus.


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## rruff (Feb 28, 2006)

danl1 said:


> There is the Khamsin to be considered, which except for the empty hole is close to what we're talking about. At 1895g for the set, it's tough to consider that an argument in favor.


I don't know why you used the Khamsin as an example... that is a cheap wheelset so of course they will be heavy. 

The weirder thing is that they are using G3 on the *front*! I thought Campy had gotten away from that... it makes absolutely no sense to me. I've never seen one up close, though... do they do something different to balance the tension?... or do they just let the stiffness of the rim take care of it?


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## bismo37 (Mar 22, 2002)

I have a new campy Vento with G3 pattern on the front... I haven't ridden them at all yet due to the weather. Campy alternates the triplet spoke pattern on the front wheel unlike the single spoked NDS on the back wheel. Kinda scary if i break one of the singlet spokes.

Here are a couple crappy photos showing the alternating triplet pattern on the Campy G3 front wheel.


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## rruff (Feb 28, 2006)

jeebus said:
 

> Here are a couple crappy photos showing the alternating triplet pattern on the Campy G3 front wheel.


Thanks for the photos. It sure looks like the single spokes need to be at twice the tension of the double spokes to make the wheel true. Can you confirm that that is the case? If you don't have a tensiometer, you can pluck the spokes to see how different the tone is...


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## bismo37 (Mar 22, 2002)

No tensiometer, but there is an audible difference tone when plucking spokes. The single spoke is higher pitched than its 2 contralateral spokes. Interestingly, when plucking the 2 contralateral spokes, i also noted a slight difference in tone between the two. Hmmm, I'm not too sure how well these new wheels are truly tensioned. I would expect the two contralaterals to have similar tension. They spin true and are round. I guess the only way to test how well built they are is to ride the hell out of them...

One thing i was not aware of is that on each wheel there is one absurdly thick spoke in the triplet nearest the valve stem... Is this supposed to act as a counterbalance for the rim joint on the other side? Looks kinda goofy now that i have noticed it.


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## rruff (Feb 28, 2006)

A *slight* tonal difference isn't a big problem... but I still don't get using G3 on the front wheel. Is the single spoke the same diameter as the doubles? They look the same in the photo. If so then the double spokes will go slack when you hit a bump... at least before the single spoke does. Maybe they just cranked up the tension on the singles... but then they'd need to beef up the rim at that point, plus the stress in the single spoke could get pretty high with side loads...

I don't know... I can see reasons *not* to do it, and no good reasons *to* do it... except looks. It's freaky really... they balanced the tension in the rear wheel but then unbalanced it in the front so it would look the same. I guess they aren't falling apart, so it isn't terrible... but it isn't optimal. They don't do this with their higher-end wheels... those are evenly spaced and radial in the front.


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## danl1 (Jul 23, 2005)

rruff said:


> Or you could say it has *less* of the bad parts of either... and that extra hole is not a problem. The stress should be less than if a spoke was attached. Getting rid of material between the spoke attachment points is a good way to optimize the strength/weight of the rim.


With a skipped spoke (G3, too), the tension of the remaining spokes are effectively trying to pull the wheel out of round, into a polygon with vertices at the center of the unsupported span... right where that skipped hole is. There is no common structure that gains strength by having a hole drilled in it. However, add a spoke in there, and it keeps that otherwise bend at that point from happening. 

A wheel won't be tensioned enough to be brought out of round in this way, but it will concentrate stresses around those empty spoke holes in the rim, inviting earlier damage than otherwise on impact.


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## danl1 (Jul 23, 2005)

I really only brought them up because they're more conventionally built than G3's, with fairly normal spokes and not-parallel lacing. They appear similar to a skipped-hole build in the rim spacing. Not exactly, but closer. 

Yeah, they're cheap so it's not a fair tool in argument - but with conventional spokes and an obviously heavy rim, maybe it's better than we'd care to think.

I agree that the front wheel is weird. Really shows how amazing a structure the bicycle wheel is - that you can do something that screwed up with it and still have it turn out OK.


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## Ligero (Oct 21, 2005)

danl1 said:


> With a skipped spoke (G3, too), the tension of the remaining spokes are effectively trying to pull the wheel out of round, into a polygon with vertices at the center of the unsupported span... right where that skipped hole is. There is no common structure that gains strength by having a hole drilled in it. However, add a spoke in there, and it keeps that otherwise bend at that point from happening.
> 
> A wheel won't be tensioned enough to be brought out of round in this way, but it will concentrate stresses around those empty spoke holes in the rim, inviting earlier damage than otherwise on impact.


Technically what you are saying is true but the rim is not stressed enough for that small hole to make a difference. Every rim made has a very large hole drilled in it for the valve stem and you very rarely ever see a rim fail at the valve hole. BMX rims have used holes drilled in between the spoke holes as a way to lighten rims for years.


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## Mark McM (Jun 18, 2005)

danl1 said:


> With a skipped spoke (G3, too), the tension of the remaining spokes are effectively trying to pull the wheel out of round, into a polygon with vertices at the center of the unsupported span... right where that skipped hole is. There is no common structure that gains strength by having a hole drilled in it. However, add a spoke in there, and it keeps that otherwise bend at that point from happening.


Sorry, but this explaination makes no sense, for a lot of reasons. Firstly, the spoke (nipple) can't add strength to the hole, because there is too much clearance around it (spoke holes are purposes drilled over-sized so that the nipple can rotate as necessary to the keep the spoke aligned). Secondly, having a spoke in the hole _increases_ the localized stress on the rim due to the spoke tension, not decrease it - that's why rim cracks occur around the spokes. Without a spoke in the hole, there is actually less stress at the spoke hole than at a spoke hole that does have a spoke in it.

Besides which, if holes in the rim were so bad, why isn't there a problem with drilling a much larger hole for the valve? Rim cracks occur at the spokes, not at the valve.


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## danl1 (Jul 23, 2005)

Mark McM said:


> Sorry, but this explaination makes no sense, for a lot of reasons. Firstly, the spoke (nipple) can't add strength to the hole, because there is too much clearance around it (spoke holes are purposes drilled over-sized so that the nipple can rotate as necessary to the keep the spoke aligned). Secondly, having a spoke in the hole _increases_ the localized stress on the rim due to the spoke tension, not decrease it - that's why rim cracks occur around the spokes. Without a spoke in the hole, there is actually less stress at the spoke hole than at a spoke hole that does have a spoke in it.
> 
> Besides which, if holes in the rim were so bad, why isn't there a problem with drilling a much larger hole for the valve? Rim cracks occur at the spokes, not at the valve.


With all respect, you're looking at the hole, rather than at the whole. The valve hole argument is a red herring. It's not the hole that is a concern, but the placement of the hole. On a G3, they put it near one of the spoke clusters rather than in the middle of the span. Apparently the Campy engineers agree with me, though that doesn't mean that I'm not wrong. 

My point was not that the spoke strengthed the hole - that's obviously wrong, as you've pointed out. The point was that a spoke supports an otherwise unsupported span of rim, one that was made even weaker in this instance by adding (skipping) a hole. 

G3 wheels display noticeable lobes, or out-of-roundness 'hops' between the spoke clusters. It's minor, but it's there, and represents unbalanced stress in the nature of the build. Adding a structural weakness at the midpoint of that span (as with an unused hole) can't be a good thing. 

Wheels crack at the spoke holes because that's where the stress is applied. A wheel doesn't fail because it's squeezed vertically, so much as that as it is squeezed vertically, it bulges horizontally. Overload a balanced, properly-tensioned wheel and it's the 3 and 9 o'clock spokes and holes that fail - not the 6 or 12 o'clock. On a skipped-spoke wheel, the empty holes serve as 'fold here' score-lines for rim origami when a potentially destructive load is applied. However minor, it reduces the strength of the system by allowing the rim to go out-of-round faster, and so increasing the stresses on the supporting spokes. Compared to wheels without the extra holes or to wheels with balanced spoking, it will fail sooner, even if not necessarily at that specific location. *

I'd like to see destruction testing or high-quality FEA of a 32/24 triplet (even rim spacing, x1NDS) compared to a 36/27 (skipped rim hole, radial NDS.) Build parameters (hub, rim, and spoke choices; build tension) could probably take it either way, but my money is on the 32/24 staying intact and round longer.

* Edit: This is an oversimplification of the dynamic stresses on a wheel. Still, the 3-and-6 portion of the argument is valid, only for more than just the reasons given.


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## Mark McM (Jun 18, 2005)

danl1 said:


> With all respect, you're looking at the hole, rather than at the whole. The valve hole argument is a red herring. It's not the hole that is a concern, but the placement of the hole. On a G3, they put it near one of the spoke clusters rather than in the middle of the span. Apparently the Campy engineers agree with me, though that doesn't mean that I'm not wrong.


I'm afraid that your error has occured because you looked at the hole, and not the whole. If you looked at the whole wheel, you'd see why the Campagnolo designers put the valve hole where the did. Traditionally, the valve hole is alwayd directly opposite the seam. The Campagnolo G3 wheels all have and odd number of 3-spoke clusters. The didn't want to put a spoke cluster at the seam, because the nipples don't seat well in the sleeve used to hold the joint together. They couldn't put the seam directly betwee a pair of spoke clusters, because the valve hole would end up inside a spoke cluster. So, they simply aligned the spoke clusters a bit offset from the both seam and the valve hole.



danl1 said:


> My point was not that the spoke strengthed the hole - that's obviously wrong, as you've pointed out. The point was that a spoke supports an otherwise unsupported span of rim, one that was made even weaker in this instance by adding (skipping) a hole.


This doesn't seem to bother Rolf, Bontrager, and other makers of paired spoke wheels. They all put the valve hole directly in the middle between spoke pairs.

Like any other part, the rim is only as strong as its weakest link. Since there are so many other, weaker points and more heavly stressed points on a rim than a single emppty spoke hole, skipping a spoke hole (regardless of its position) is a non-issue in regard to rim strength.



danl1 said:


> Wheels crack at the spoke holes because that's where the stress is applied. A wheel doesn't fail because it's squeezed vertically, so much as that as it is squeezed vertically, it bulges horizontally.


I'm not sure what you mean by this. Cracks form from tension stresses, not compression stresses - so cracks form where the rim material is "stretched", not where it is "squeezed".



danl1 said:


> Overload a balanced, properly-tensioned wheel and it's the 3 and 9 o'clock spokes and holes that fail - not the 6 or 12 o'clock.


From this, I gather that you don't understand how wheels fail. When overloaded, wheels don't fail due to spoke failure, and rarely due to spoke pull-through - they fail due to buckling of the rim. When a wheel is loaded, there is virtually no increase in spoke tension - wheel loads are supported by decreases in tension at the bottom of the wheel. When the bottom spokes become completely de-tensioned, and the bottom of the rim is no longer supported, the rim at the bottom is free to buckle (fold over).



danl1 said:


> On a skipped-spoke wheel, the empty holes serve as 'fold here' score-lines for rim origami when a potentially destructive load is applied. However minor, it reduces the strength of the system by allowing the rim to go out-of-round faster, and so increasing the stresses on the supporting spokes.


Any and all holes in the rim (including filled spoke holes) can serve as the weak point for rim failure. Generally the weakest point on the rim (and the most likely place for a buckle to iniatiate) is the valve hole, and the next weakest is usually the seam. A few extra unfilled spoke holes won't make much of a difference if a rim is loaded to buckling.



danl1 said:


> I'd like to see destruction testing or high-quality FEA of a 32/24 triplet (even rim spacing, x1NDS) compared to a 36/27 (skipped rim hole, radial NDS.) Build parameters (hub, rim, and spoke choices; build tension) could probably take it either way, but my money is on the 32/24 staying intact and round longer.


I would tend to bet the other way. The 36/27 wheel has more spokes to begin with (distributing the load over more points), and when spokes start to detension, the closer grouping of right/left spokes would tend to give the rim better balanced lateral support.


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