Corima Viva on Record hubs?

ugo.santalucia

thecycleclinic wrote:

Feel free anyone to comment as this statement CX-ray are stiffer than Laser I am having real trouble with as I cannot see any evidence for it. Ugo's comments seem to be a bout personal experience of how a wheel behave under torque but that involves tortional stiffness too.

That is my logic anyway.

Last I say on the topic, which is off topic and it's becoming tedious for other users

I tend to give an explanation to empirical results, rather than throwing down maths & physics to which wheels need to obey. A rear wheel built with 24 CX ray spokes is a pretty stiff wheel.. take a Wheelsmith Race 23 for instance, or one like this
http://paolocoppo.drupalgardens.com/med ... tail/16/91

the evidence is that it is stiff, the same wheel built with Laser spokes is not.
That's the evidence, the empirical result... then whether my theory makes sense or not is questionable, but you can't deny the evidence, because that's where the speculation starts, it cannot be the end point... the wheel cannot do what your maths want it to do.

In other words maths serve to explain reality and not vice-versa... I guess it's the clash of two different school of thought... you studied maths and physics, I studied chemistry and materials... there you go...

cycleclinic

Yes I think it should end too. I do not deny wheelsmith Race 23 wheelset is not stiff. I also have built many stiff 24 spoke rear wheels with CX-rays I am not doubting for a second they cannot build a stiff wheels, I have also built many 24 spoke rear stiff wheels with lasers. I have also built the same wheelset with CX-ray and with lasers I really cannot feel the CX-ray wheelset being any stiffer. I might have to test this and measure. When I do I will let you know the results.

BenderRodriguez

thecycleclinic wrote:

Feel free anyone to comment as this statement CX-ray are stiffer than Laser I am having real trouble with as I cannot see any evidence for it.

Surely, how a spoke behaves when bent is pretty much irrelevant to how stiff the resultant wheel will be? Just consider how stiff a wheel can be built with very flexible 'carbon ribbon' type 'spokes'. All that matters is how they behave in tension.

Why a wheel built with X-Ray spokes will be stiffer than one built with Laser spokes is simple, and is all to do with their relative cross-sectional area, and possibly their strength in tension which is likely to reflect how relatively 'stretchy' they are.

A laser spoke has a cross sectional area of 1.77 mm2. An X-Ray spoke has a cross sectional area of 1.98 mm2. Hence, all else being equal, the X-Ray will build a stiffer wheel. Also, the tensile strength of a Laser spoke is 1500 N/mm2, giving a breaking strain of 2655 N. An X-Ray spoke has a tensile strength of 1600 N/mm2, giving a breaking strain of 3168 N, not far off that for a 'Race' butted spoke (2.54 mm2 and 1300N/mm2 equating to 3302 N), and of course the X-Ray has a much higher fatigue resistance than a standard 'Race' spoke.

thecycleclinic wrote:

Cx rays are aero spokes which you are going to build with a 32 spoke wheel with a shallow rim. You have lost all ypur areoness if that is even a word with that combo... The aero benefit of cx rays is not great and not enough to notice which is why they are best used on race wheels were every last Advantage is wanted.

If the aero' advantage to be had from using 24 X-Ray spokes them over normal spokes is worthwhile, it follows that the advantage when using 32 of them as opposed to 32 normal spokes will be greater still, even if a better way to make a wheel more aero' is to lose a few of the spokes.

We also need to remember that there is more than one factor which contributes to what makes a wheel aerodynamic. One is the rotational component, which is largely independent of the rim used, another is the translational component as the whole wheel moves forward through the air, and this is affected by the rim shape. For a pair of climbing wheels, as opposed to time trialling wheels, it seems likely that there is not all that much advantage to be had from using an aero rim, at least at typical 'punter' climbing speeds. Of course, with a more slowly rotating wheel the benefits to be had from X-Ray spokes will also be less, but the benefit will still be there. Also the X-Rays will be lighter than 'Race' spokes, build a stiffer wheel than Lasers and have a higher fatigue life than either.

on-yer-bike

ugo.santalucia wrote:

on-yer-bike wrote:

What number on my blue Park tension meter is 1200Nm using 1.5 mm spokes?

Don't you have the conversion chart?

Yep. The wheels I built are around 1210 Newtons DS and front radial. The NDS is a lot less and first time out fell to bits. I have now loctited the NDS and only a couple came lose.

ugo.santalucia

on-yer-bike wrote:

Yep. The wheels I built are around 1210 Newtons DS and front radial. The NDS is a lot less and first time out fell to bits. I have now loctited the NDS and only a couple came lose.

If you used laser or DT revs at the rear (contrary to my advice... :evil: ), then you might have left some wind-up while building them, which might be the reason. Also, because those spokes have more bend, they tend to come loose quicker... just not the first time you ride them...

Laser (or revs) and threadlock is not a good combination

on-yer-bike

ugo.santalucia wrote:

on-yer-bike wrote:

Yep. The wheels I built are around 1210 Newtons DS and front radial. The NDS is a lot less and first time out fell to bits. I have now loctited the NDS and only a couple came lose.

If you used laser or DT revs at the rear (contrary to my advice... :evil: ), then you might have left some wind-up while building them, which might be the reason. Also, because those spokes have more bend, they tend to come loose quicker... just not the first time you ride them...

Laser (or revs) and threadlock is not a good combination

Why is Loctite 222 with Revs not a good combo?
I didnt oil the NDS threads.
Is there any easy way of telling if the spokes are twisted?
Im using it on the turbo to see if it stays true. Not sure if I'll ever dare go very far on them yet alone send my wife out on them. Look nice though...

ugo.santalucia

on-yer-bike wrote:

Why is Loctite 222 with Revs not a good combo?
I didnt oil the NDS threads.
Is there any easy way of telling if the spokes are twisted?
Im using it on the turbo to see if it stays true. Not sure if I'll ever dare go very far on them yet alone send my wife out on them. Look nice though...

Because once it sets it might prove hard to unlock the spoke, it will wind on itself... you might just get away being 222 and not a stronger one, but it depends how much there is of it... and Loctite likes brass!

The wind up can be removed by de-stressing the wheel and riding the wheel... ultimately you should avoid building it up in the first place by backing off one quarter every time you load tension on the spoke.

Thing is, you have used 24 Revs on a rear wheel with a shallow rim and a hub with a narrow flange, which is nice when you lift the wheel, but not when you ride it... too much flex, plenty of chances for the spokes to come loose. I did advise for DT comp at the rear and I stand by that

cycleclinic

thecycleclinic wrote:Feel free anyone to comment as this statement CX-ray are stiffer than Laser I am having real trouble with as I cannot see any evidence for it.

Surely, how a spoke behaves when bent is pretty much irrelevant to how stiff the resultant wheel will be? Just consider how stiff a wheel can be built with very flexible 'carbon ribbon' type 'spokes'. All that matters is how they behave in tension.

Why a wheel built with X-Ray spokes will be stiffer than one built with Laser spokes is simple, and is all to do with their relative cross-sectional area, and possibly their strength in tension which is likely to reflect how relatively 'stretchy' they are.

A laser spoke has a cross sectional area of 1.77 mm2. An X-Ray spoke has a cross sectional area of 1.98 mm2. Hence, all else being equal, the X-Ray will build a stiffer wheel. Also, the tensile strength of a Laser spoke is 1500 N/mm2, giving a breaking strain of 2655 N. An X-Ray spoke has a tensile strength of 1600 N/mm2, giving a breaking strain of 3168 N, not far off that for a 'Race' butted spoke (2.54 mm2 and 1300N/mm2 equating to 3302 N), and of course the X-Ray has a much higher fatigue resistance than a standard 'Race' spoke.

thecycleclinic wrote:Cx rays are aero spokes which you are going to build with a 32 spoke wheel with a shallow rim. You have lost all ypur areoness if that is even a word with that combo... The aero benefit of cx rays is not great and not enough to notice which is why they are best used on race wheels were every last Advantage is wanted.



If the aero' advantage to be had from using 24 X-Ray spokes them over normal spokes is worthwhile, it follows that the advantage when using 32 of them as opposed to 32 normal spokes will be greater still, even if a better way to make a wheel more aero' is to lose a few of the spokes.

We also need to remember that there is more than one factor which contributes to what makes a wheel aerodynamic. One is the rotational component, which is largely independent of the rim used, another is the translational component as the whole wheel moves forward through the air, and this is affected by the rim shape. For a pair of climbing wheels, as opposed to time trialling wheels, it seems likely that there is not all that much advantage to be had from using an aero rim, at least at typical 'punter' climbing speeds. Of course, with a more slowly rotating wheel the benefits to be had from X-Ray spokes will also be less, but the benefit will still be there. Also the X-Rays will be lighter than 'Race' spokes, build a stiffer wheel than Lasers and have a higher fatigue life than either.

your facts are wrong a CX-ray spokes has a cross sectional area very close to that of a Laser spokes. 1.98mm^2 is the aera of a rectangle of 2.3x0.9mmm but a CX-ray is not a rectangle, it is along way from that so if we are going to quote data we need to clear exactly what we are quoting.

I have never worked out how to use the quote function properly

A spoke does not behave different under tension. A spoke stiffness is not dependent of tension it is a inherent property of the spoke's young modulus, it shape (area of moment of inertia) and length. That is it. Carbon fibre spokes are used in wheels with very stiff rims that why then turn out stiff. I build some 24 spoke rear wheels with Lasers spokes and that significantly stiffer than a 32 spoke wheel with Race spokes, why because of the rims used.
Did one this afternoon with 32 lasers on the rear (for a very light rider) using a DT Swiss rim. This wheel is stiffer than a 32 spoke wheel on the same hub with Race spokes. The rim makes all the difference.

Wheels are mostly aero due to the lack of spokes not because the wheels have ovalised spokes. Aero spokes help at the margins.
The other components to how aero a wheel
1)is is spoke length as that is more exposed surface area,
2) the ERD of the rim the lower this is the faster the spokes the the nipple end when the wheel rotates,
3) rim depth and profile make a difference as deeper rim with the various profiles you see these days keep the air flow from becoming too turbulent.
The Nemesis rim is a shallow box section rim so when air passes over that rim turbulence immediately ensues. It is not an aero rim and a 32 spoke one with CX-ray will not improve matter by any significant amount.

Fatigue performance of a Cx-ray may be the same as a laser. The fatigue performance figures that Sapim produce are suspect. Based on the numbers they state CX-ray would last 4300 odd miles. Obviously that is wrong.

Fatigue is a function of the % unloading each cycle. A CX-ray, Laser and Race spoke are all made form the same wire stock and have the same diameter at the elbow. I could direct you to various papers on fatigue if you like. Sapim's fatigue claims will be an accelerated fatigue test but we do not know if the conditions of the test for each spoke are the same, they may not be be. Let me elaborate. The fatigue performace of CX-ray steel is pretty much the same as Laser steel, it is the same steel.

The strength data you quote is meaningless, spokes do not fail by being stretched till they are broken to they. The reason why the CX-ray spoke has a higher failure strength is because it has undergone a extra process, making it oval. This will work harden the steel and improve strength but as I have mentioned strength for spokes is an almost irrelevance. Extra work hardening does not nescessarily improve fatigue performace either.

Given a CX-ray and Laser are the same mass and have the same cross sectional area they will behave very similarly. The stiffness difference though come form the CX-rays shape. They are stiffer "along width" and less stiff/same laterally (along there length), as am unclear the effect crossing has on lateral stiffness as there may be an along the width effect.

I am not saying that CX-rays are not a good spoke, I would not not use them if I they were not what I am saying they will be of little benefit to you in your planned wheel. I also would take all of sapims claims with a pinch of salt. they claim on there site that increasing spoke tension increases wheel stiffness. That was bebunked a while back (josh brandt's results are the most accessible) but A -level physics also predicts this. So any claims by Sapim to me are just marketing and if they make one blatantly false claim then all other claims are called in question.

They make good spokes though.

cycleclinic

For on yer bike
The park gauge is O.K for relative tension but it over reads by 10-20%. I have three gauges now and the only one I really trust is the DT Swiss tensio (as my sapim gauge needs calibrating again). For spokes tensioned the 1200N on the Park gauge the DT tensio reads a bit over 1000N. 24 Laser spokes on a shallow rim with a hub is only suitable for very very light rider like youth racers. Even then the rim cannot be too shallow.

The reason why your build fell to bits is for two reasons. too much flex means the NDS spoke nipple unwound. Lociting them will stop this by if they loose tension alot then they will fatigue quickly. The other common reason Laser spoke and CX-ray for that matter (and race) need to stretched when building or the first time you ride when you apply torque they will stretch more and the tension will drop - wheel fall apart. When building in addition to the usual stress relieving I and you should grasp pairs of spokes when you are 75% tension for example and really squeeze so much that your hands hurts. I do this 3 to 4 times for each pair of spokes yes it hurts. This stretches the spokes and there is a measurable tension drop. Do this and the wheel when fully tensioned will retain the tension you set and not fall apart.

Wind up is resolved as ugo said by stress relieving and is managed by adding tension (when the tension is high) in 1/4 turns or 1/2 turns. Also sometimes there will be one bad nipple or wind will occur at high tension because you are running out of nipple thread. This can happen sooner than you might expect as laser spoke will stretch by 0.45mm under 1200N tension and the extra load you put on them then grasping pairs will increase that.
Proper lubrication of the spoke threads is critical too.

BenderRodriguez

thecycleclinic wrote:

...a CX-ray spokes has a cross sectional area very close to that of a Laser spokes. 1.98mm^2 is the aera of a rectangle of 2.3x0.9mmm but a CX-ray is not a rectangle...Given a CX-ray and Laser are the same mass and have the same cross sectional area they will behave very similarly.

OK, good point. I had assumed that X-Rays were a similar shape to those in my old Mavic wheels.

thecycleclinic wrote:

the CX-ray spoke has a higher failure strength is because it has undergone a extra process, making it oval. This will work harden the steel and improve strength but as I have mentioned strength for spokes is an almost irrelevance.

But if spoke 'A' has a higher tensile strength than spoke 'B' although it is made of the same basic material, and so will show the same curve for yield behaviour, won't the spoke with the higher tensile strength show less elastic deformation for the same load?

thecycleclinic wrote:

I build some 24 spoke rear wheels with Lasers spokes and that significantly stiffer than a 32 spoke wheel with Race spokes, why because of the rims used...

So those Corima rims would have given me a significantly lighter, stiffer wheel?

thecycleclinic wrote:

Wheels are mostly aero due to the lack of spokes... Aero spokes help at the margins...

thecycleclinic wrote:

The Nemesis rim is a shallow box section rim so when air passes over that rim turbulence immediately ensues.

So, what makes the biggest contribution, the rim or the number of spokes? Your comment above about rim shape seems to suggests it is the rim.

Also, I am also not so sure that the benefit of aero spokes is 'marginal', as compared with building a lower spoke count wheel. For example, if I build a 24 spoke wheel using round 1.8 mm 'Race' spokes, then the total cross sectional width of those spokes is 43.2 mm. On the other hand, if I build a 32 spoke wheel with 0.9 mm 'X-Ray' spokes, the total cross sectional width of these is 28.8 mm. Even if I use 1.5 mm 'Laser' spokes for my 24 spoke wheel, then the cross sectional width of those spokes is still more, at 32mm. So, in this example, the benefit of using aero spokes would seem to be greater than reducing the spoke count, especially considering that an aero spoke should have less drag than a round one.

thecycleclinic wrote:

So any claims by Sapim to me are just marketing and if they make one blatantly false claim then all other claims are called in question.

Isn't that a logical fallacy?

Edit: Moved link to new post.

cycleclinic

the last comment first. If someone lies (even though you know they know the truth) once do you believe there next claims? If Sapim who should know better are mistaken about a fundemental issue like the one I highlighted then surely there other claims might be suspect.

Lower spoke count I think (although without doing wind tunnel tests it is difficult to tell) give the biggest improvement. This requires stiffer rims which mean deep so aero rims, short spokes (short spoke have a higher spring constant) and thin gauge spokes (as stiff rims means thin butted spokes can be used) go together. This make most of the aero difference. Aero spoke will add a little bit but it is not the main effect.

Wheels are test for there aerodynamics at 30 mph. A pair of wheels 36 spoke and a deep carbon very low spoke count wheelset set may show 20W difference in power to over come drag at that speed. Are you know telling me that those couple of mm^2 in cross sectional area on your 32 spoke wheels is going to make anything more than 1-2W of difference. Even if you look at wheel tests a fulcrum racing 7 has lower aerodynamic drag than the Mavic Kyrserium ES 2006 - I am not lying by 0.5W at 50 km/h. Fulcrum racing 7 using a thick round spoke were as the mavic uses a bladed spokes. And there is no difference between them. So yes marginal gains for areo spokes even for the CX-ray vs Lasers. a couple of W at the most I would think at speed. Wind tunnel test are needed to confirm though.

on-yer-bike

Maybe I'll rebuild the rear using Comps.
I notice on the Park gauge that the needle in the resting position is behind (left of) the zero and I'm not sure if this is correct, but its how it came.

cycleclinic

Good idea but graps the spokes to strech until your hands really hurt if your hands do not hurt when building a wheel you have not de stressed or stretch the spokes enough. I have got used to the discomfort, it is no longer pain. Do this with CX-rays still hurts.

BenderRodriguez

thecycleclinic wrote:

Wheels are mostly aero due to the lack of spokes... Aero spokes help at the margins...

To return to this point. The page below includes an illustration that throws some light on the drag factor that I mentioned earlier. This indicates that an 'X-Ray' spoke has a turbulent wake of just 0.5 mm, as compared to one of 1.8 mm for a standard butted spoke. So, 32 'X-Ray' spokes create a total turbulent wake 16 mm wide, as opposed to one 43.2 mm wide with 24 standard butted spokes.

Then of course spokes have length as well, so if we take a nominal spoke length of 290 mm for each wheel, the 32 spoke wheel built with X-Rays creates a total turbulent wake of 32 x 0.5 x 290 = 46.4 cm2. Conversely, our 24 spoke wheel laced with 'Race' spokes creates a total turbulent wake of 24 x 1.8 x 290 = 125.3 cm2. That is a difference of 78.9 cm2, or 157.8 cm2 for the pair.

To look at it another way, our pair of 24 spoke wheels laced with standard 'Race' spokes will be creating an additional turbulent wake equivalent to attaching a flat 'fan blade' 20cm long and 8 cm wide to one of the wheels.

If we are comparing just 32 spoke wheels it seems that the benefit of using 'aero' spokes will be even greater. For example, the total wake created using 'Race' spokes will be 32 x 1.8 x 290 = 167 cm2, or 334 cm2 for the pair. With X-Rays the total area for a pair of wheels is 92.8 cm2 , or 241 cm2 less, equivalent to a flat 'fan blade' 24 cm long and 10 cm wide!

OK, so things aren't that simple due to the turbulence created by the rim and so forth, but I would doubt that all the benefit is lost.

http://www.rouesartisanales.com/article-15505311.html

It seems that Zipp would also disagree with you regarding the 'marginal' importance of spoke shape:

Perhaps the most noticeable feature of this graph is the very high wattage of the round spoked 46mm deep wheel. Requiring more than 10 additional watts to spin when compared to the almost identical bladed spoke 46mm deep wheel, with which it shared nearly the identical drag curve!

...Even the best rim designs and intentions can be negated by poor spoke choice. Round spokes offer very good strength and fatigue performance, but hold a substantial aerodynamic performance penalty and should be avoided in high performance aerodynamic wheels. The aerodynamic power differential between round and oval spokes is sufficiently higher than any possible weight savings, equating to tens of pounds of additional weight to the bike, so round spokes should be avoided regardless of weight advantage.

http://www.zipp.com/_media/pdfs/technol ... pe.pdf.bak‎

BenderRodriguez

thecycleclinic wrote:

If Sapim who should know better are mistaken about a fundemental issue like the one I highlighted then surely there other claims might be suspect.

The rational thing to do is to evaluate each claim made on its own merits, not to accept everything someone says because you felt they were right previously, or reject everything someone says because they were once show to be in error in the past. (For example, recommending the use of alloy nipples when the consensus view is that they are crap. )

BenderRodriguez

thecycleclinic wrote:

I build some 24 spoke rear wheels with Lasers spokes and that significantly stiffer than a 32 spoke wheel with Race spokes, why because of the rims used...

Perhaps this depends on what you mean by stiffness. For most a wheel would not be considered to be 'stiff' if it rubbed against the brake blocks every time the rider swayed the bike from side to side on a climb or when sprinting.

Both the links below argue that, no matter how stiff the rim, the use of a reduced number of spokes can result in brake rub when climbing or sprinting as the spokes flex whilst the rim maintains its shape. So, even with a stiff rim, overall the wheel can still lack stiffness, something that can only be remedied with more or heavier spokes.

For example:

When you start climbing or sprinting on a carbon wheel, the stiff rim tends to want to stay perfectly straight – relative to itself.

This gets compounded by the fact that most “race” wheels have thin aerodynamic spokes – AND not very many of them. On top of that, in very recent years, we have also seen carbon rims grow in both width and depth – subsequently gaining both lateral and radial stiffness.

What this adds up to is the perfect wheel storm: An astoundingly stiff, deep-section carbon rim – strapped on to a handful of thin aero spokes. The stiff rim can literally overpower the spokes. If your rim rubs your rear brake pads, this is probably why.

http://www.slowtwitch.com/Tech/Debunkin ... _3449.html

...a box section rim with a high spoke count can have two times less deflections between the brake pads, than a wheel with the same construction but a deep rim and a low spoke count!

To quote a few examples: this is the case for the Lightweight Standard G3/Ventoux, the Campagnolo Bora/Hyperon, but also the Shimano C24TU/C50TU, Speedcomposites, Easton EC90 SLX, etc.

The stiffer wheel is the one with the deeper rim, but if you rely on the deflections between the brake pads, this is the inverse…!

http://www.rouesartisanales.com/article-23159755.html

It seems that for a truly 'stiff' wheel one needs both a stiff rim and a high spoke count.

cycleclinic

Given Sapim do not state the condtions for the fatigue test they cannot be trusted can they. Also as I pointed out there fatigue result mean a two thousand miles from there race spokes. I have wheels that done 4 times that so those numbers are completly meanginless.

Stiff rims and 32 spokes is stiff but a stiff rim and 24 spokes can be very stiff. Think velocity Deep V on Chris king hubs with Laser spokes that wheel barely flexed at all. 24 spoke rear built with Kinlin XR-300's or XC-279's are similarly stiff. I have built stupidly stiff wheels with a 32H DT Swiss RR585, Sapim Race spokes on Miche hubs (for a heavy rider). Stiff does not describe how stiff but it was stiffer than most people will need.

I do not base my wheel stiffness assessments on deflection between brake pads that was an assumption you made there. I base in on how the wheel feels when stress relieving i.e loading the rim which is something I have do to ensure the wheel is stable. You get a very good idea of the relative stiffness of wheels that way.

32 spoke wheels are a bit of a windmill putting aero spokes in does not change that. Also with a shallow rim like the nemesis as soon as the air passes over the rim it is turbulant and therefore turbulant air is hitting the spokes meaning using aero spoke is almost pointless. Also on the rear wheel air passing over the seat tube make the air turbulant even before it hit the box rim, so there is even less point on the rear wheel. What ever way I look at this CX-ray on a 32 spoke wheel with nemesis rims is pointless. Build two and ride them both in the same bike I can assure you will not notice the difference except for your wallet being lighter.

I am fully aware of the low turbulant wake of CX-ray but we are comparing in this thread CX-ray to Lasers which have a smaller diamater so the differences are smaller. Lowering the spoke count is still the best way of reducing drag followed by aero spokes.

BenderRodriguez

thecycleclinic wrote:

I do not base my wheel stiffness assessments on deflection between brake pads that was an assumption you made there. I base in on how the wheel feels when stress relieving

I would have thought that most people would be more interested in how a pair of wheels perform in a real world situation, and brake rub does seem to be an endemic 'characteristic' of many modern 'aero' wheel with super-stiff rims but minimal spokes.

thecycleclinic wrote:

32 spoke wheels are a bit of a windmill putting aero spokes in does not change that...I am fully aware of the low turbulant wake of CX-ray but we are comparing in this thread CX-ray to Lasers which have a smaller diamater so the differences are smaller. Lowering the spoke count is still the best way of reducing drag followed by aero spokes.

The figures show that having few spokes is not the only way of getting an aero advantage, and having few spokes does not in itself guarantee good aero performance, as Zipp have found. This is the case even if we use Laser spokes (whose lack of stiffness makes them unsuitable for many applications) as our comparison. Twenty-four, 290 mm long 'Laser' spokes create a total turbulent wake 24 x 290 x 1.5 mm = 104.4 cm2, still more than double that for a 32 spoke wheel built with X-Rays.

thecycleclinic wrote:

Also on the rear wheel air passing over the seat tube make the air turbulant even before it hit the box rim, so there is even less point on the rear wheel.

And yet, despite all the turbulence caused by the rotating front wheel, frame, riders legs etc. etc. a rear disc is still significantly faster than any spoked wheel, so it seems that even in already turbulent air the benefit to be had from avoiding creating further turbulence is not completely lost.

ugo.santalucia

thecycleclinic wrote:

Given Sapim do not state the condtions for the fatigue test they cannot be trusted can they. Also as I pointed out there fatigue result mean a two thousand miles from there race spokes. I have wheels that done 4 times that so those numbers are completly meanginless.

Agree, those fatigue numbers in the absence of load and frequency and details of the experiment don't mean anything. Pillar publish their fatigue tests with more details and their numbers are about one order of magnitude lower than Sapim... so clearly there isn't a standard test in the industry... which means it's all a waste of time

cycleclinic

You are obviously not convinced. You need to build wheels with CX-rays and with round spokes and come to you own conclusion. I have and I stated my conclusions. You need to dot he same Benderrodriguez.

The problems is with statements about total turbulant area is you assume the aero drag is some sort of linear thing it isn't it vastly more complicated and very non linear so just because a 24 lasers spokes has twice the turbulent area of 32 CX-rays does not mean that the drag is half as much. Assumption are a dangerous thing.

BenderRodriguez

thecycleclinic wrote:

The problems is with statements about total turbulant area is you assume the aero drag is some sort of linear thing it isn't it vastly more complicated and very non linear so just because a 24 lasers spokes has twice the turbulent area of 32 CX-rays does not mean that the drag is half as much.

Maybe, but my central point is that you were wrong to claim that reducing the number of spokes is the most effective way to improve the aerodynamic performance of a wheel, with spoke shape only having a minimal benefit 'at the margins'. As studies by people such as Zipp have found (unless you want to argue that they are 'lying' too) spoke shape plays at least as important a role. Ok, so perhaps a 32 spoke wheel built with X-Ray spokes is, to use your terminology, 'a windmill', but it is no where near as big a 'windmill' as a 24 spoke wheel built with round spokes, even if we use Lasers. The turbulent wake figures suggest that our 32 spoke wheel built using X-Ray spokes would still have the advantage if we reduced the spoke count in our Laser-built wheel to 20 or even 16 spokes. This is also in accordance with what Zipp report.

I would also suggest that you were also wrong to downplay the important role the number of spokes has in determining the real-world stiffness of a wheel, with plenty of low spoke count wheels suffering from excessive flex, even though they use very stiff rims, to the extent that the wheel is prone to rubbing on the brake blocks when climbing or sprinting.

adding more spokes or thicker spokes adds weight and drag. That’s life. On the flip side, you’re losing power by flexing a wheel or rubbing the brake pads. I inquired with several different manufacturers about the aerodynamic cost of adding a few spokes (i.e. using 24 rear spokes instead of 20). All replied with the same answer: The aerodynamic cost is minimal. The weight penalty is minimal. You do gain a little bit of radial stiffness – which could be seen as ride harshness – but I argue that this is a non-issue, short of extreme cases.

Why, then, don’t they use more spokes? Two words – fashion and weight. Fewer spokes look cool, and look better on-paper to the gram counters. I agreed to keep any official comments off-the-record from all manufacturers in this regard… but all of them had similar answers - sex sells.

http://www.slowtwitch.com/Tech/Debunkin ... _3449.html

cycleclinic

I never down play the importance of spokes in the stiffness of the wheel, all three components work together, rim stiffness, spoke stiffness, spoke count and bracing angles. Rider weight and power output are important factors too. Everything has to complement each other or problems will arise.

There is a reason why the nemesis comes in 32H and 36H drillings, I have built mine with Sapim Race spokes on the rear and I do not regret it, nor do I wish I had tried CX-rays as the wheel is fine as it is. They are not racing wheels after all they are wheels for club rides and riding cobbles. I have racing/TT wheels for racing only and they use low spoke counts CX-rays. All my other wheels use round spokes as I am not bothered in saving a small handful of watts at 30 mph by using CX-rays a club ride is not going at 30 mph. Everything has it place.

If you mis match the wheel to the rider and to some extend the bike then the brake rub problems you describe happen as brake rub is not a guide to how stiff your wheels are. Stiff wheels in a frame that flexs alot more can give that issue.

Build with Cx-rays it your wheel and believe who you want it is a free world.

Anyway this is all I have to say on the matter now.

BenderRodriguez

thecycleclinic wrote:

I never down play the importance of spokes in the stiffness of the wheel...

Sorry, I cant seem to see any posts by you in this thread emphasizing how a wheel can be made stiffer simply by using a few more spokes and / or heavier gauge spokes. (So much so that a 32 spoke wheel using a low-section rim can be stiffer than a 24 spoke wheel using a deep rim.) In fact many of your comments seem to imply that, as it is the rim that 'makes all the difference', what spokes you use is almost an irrelevance, with you seemingly trying to argue that for lightness, stiffness and aerodynamics, a low spoke count wheel using non-aero Laser spokes is the way to go, which is what prompted my comments.

thecycleclinic wrote:

Carbon fibre spokes are used in wheels with very stiff rims that why then turn out stiff.

("Carbon fibre spokes are used in wheels with very stiff rims and that is why they turn out to be stiff"?)

thecycleclinic wrote:

I build some 24 spoke rear wheels with Lasers spokes and that significantly stiffer than a 32 spoke wheel with Race spokes, why because of the rims used.

thecycleclinic wrote:

Lower spoke count I think (although without doing wind tunnel tests it is difficult to tell) give the biggest improvement...Aero spoke will add a little bit but it is not the main effect.

thecycleclinic wrote:

Wheels are mostly aero due to the lack of spokes not because the wheels have ovalised spokes.

Etc.

It is interesting to see just how many differences of opinion there can be when it comes even something so seemingly simple as building a wheel. Thing is, whilst one is free to 'believe who you want', when there is a difference of opinion not everyone can be right and it is necessary to weigh the evidence. In my view you have not provided any substantial evidence to support your views, with wheel stiffness seemingly being judged by how a wheel feels when you squeeze the spokes with your pain-habituated hands and you admitting that, having no wind tunnel test data, you don't actually know how relatively important the number of spokes is as opposed to their section when it comes to making a wheel more aerodynamic. Conversely, I feel that I have provided at least some evidence in support of my counter-arguments. Perhaps I would have been rather less argumentative if it were not for the fact that you are 'in the wheel-building business' as it were and so might be considered to be an 'expert'.

I know that part of your argument is that it is not possible to 'tell the difference' when riding a wheel laced with X-Rays as opposed to round spokes, but the same is probably true if you use an aero rim as well unless, perhaps, one is doing time trial speeds. Even so, to my mind, even a couple of watts advantage is worth having, and in any case my new build is focused around using tubulars, with a pair of fast, flexible tubs such as a Vittoria Service Course used at an appropriate pressure being worth perhaps 10 watts over something like a Continental Gp 4000 fitted with butyl tubes, especially over a rough road surface. This is about the same advantage to be had from losing 10 lb when climbing!

Anyhow, thanks for your input, without some of your comments causing me to think 'Hang on a minute' I might not have been prompted to read up on the topic as much as I have done.