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PostPosted: Sun Mar 17, 2013 1:36 pm 
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all carbon clinchers deform in long descent after Km's, just waita couple thousand of kilometers and you will see by yourself. But that happens to people who brake, as you ride without braking, it will never happen to you of course. Of course.

Do you know the spoke tension these can hold, or is it just "yeah quite good, a lot of spoke tension"?

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Posted: Sun Mar 17, 2013 1:36 pm 


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PostPosted: Sun Mar 17, 2013 4:35 pm 
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Liggero wrote:
....Do you know the spoke tension these can hold, or is it just "yeah quite good, a lot of spoke tension"?


FWIW, I asked a professional wheelbuilder who uses open mold rims, he said something like "I use a max tension of 130kgf on our rims (this leaves significant margin for error if someone steps on your wheel or some other random incident)."

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Last edited by carlislegeorge on Sun Mar 17, 2013 5:33 pm, edited 1 time in total.

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PostPosted: Sun Mar 17, 2013 5:09 pm 
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Liggero wrote:
all carbon clinchers deform in long descent after Km's, just waita couple thousand of kilometers and you will see by yourself. But that happens to people who brake, as you ride without braking, it will never happen to you of course. Of course.


I've already 4k km on these wheels alone....

So.... no, sorry.

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PostPosted: Sun Mar 17, 2013 8:12 pm 
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nice

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PostPosted: Sun Mar 17, 2013 11:18 pm 
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carlislegeorge wrote:
Liggero wrote:
....Do you know the spoke tension these can hold, or is it just "yeah quite good, a lot of spoke tension"?


FWIW, I asked a professional wheelbuilder who uses open mold rims, he said something like "I use a max tension of 130kgf on our rims (this leaves significant margin for error if someone steps on your wheel or some other random incident)."


this is an important data, cause it will tell you if you can go for 20-24 or 24-28 spokes. That number is not too high, so yes, it leaves a margin for "incidents", but it's not tensed enough. 150-160 would be a better mark (not for the spoke tension, but as the maximum load a decent rim should resist). Thing is that you can´t make magic, it will be either too heavy compared to alu or too weak for less spokes. 382g for a 38 carbon clincher it's very on the weak side I think. But if you leave the spokes with low tension or you just don't brake like pefendreu, there will be no issues, but it won't be stiff enough and not braking it's a extreme sport. I've seen deformed carbon clincher flanges from any brand, you name it; reynolds, enve, shimano, campagnolo, asian rims... I don't think these rims are better than enve. But I may be wrong of course.

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PostPosted: Mon Mar 18, 2013 12:59 am 
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Liggero wrote:
150-160 would be a better mark (not for the spoke tension, but as the maximum load a decent rim should resist). Thing is that you can´t make magic, it will be either too heavy compared to alu or too weak for less spokes. 382g for a 38 carbon clincher it's very on the weak side I think. But if you leave the spokes with low tension or you just don't brake like pefendreu, there will be no issues, but it won't be stiff enough and not braking it's a extreme sport. I've seen deformed carbon clincher flanges from any brand, you name it; reynolds, enve, shimano, campagnolo, asian rims... I don't think these rims are better than enve. But I may be wrong of course.


Farsports claims max tension of 300kgf for theirs rims(http://www.wheelsfar.com/38mm-clincher-wheels1250g-30g-p-220.html). Besides, the wheel's stiffness doesn't depend on spoke tension.


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PostPosted: Mon Mar 18, 2013 2:23 am 
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Hi,

Quote:
Besides, the wheel's stiffness doesn't depend on spoke tension.


Which begs the question, what does spoke tension influence if not stiffness?

Ciao, ;)

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PostPosted: Mon Mar 18, 2013 1:05 pm 
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Liggero wrote:
carlislegeorge wrote:
Liggero wrote:
....Do you know the spoke tension these can hold, or is it just "yeah quite good, a lot of spoke tension"?


FWIW, I asked a professional wheelbuilder who uses open mold rims, he said something like "I use a max tension of 130kgf on our rims (this leaves significant margin for error if someone steps on your wheel or some other random incident)."


this is an important data, cause it will tell you if you can go for 20-24 or 24-28 spokes. That number is not too high, so yes, it leaves a margin for "incidents", but it's not tensed enough. 150-160 would be a better mark (not for the spoke tension, but as the maximum load a decent rim should resist). Thing is that you can´t make magic, it will be either too heavy compared to alu or too weak for less spokes. 382g for a 38 carbon clincher it's very on the weak side I think. But if you leave the spokes with low tension or you just don't brake like pefendreu, there will be no issues, but it won't be stiff enough and not braking it's a extreme sport. I've seen deformed carbon clincher flanges from any brand, you name it; reynolds, enve, shimano, campagnolo, asian rims... I don't think these rims are better than enve. But I may be wrong of course.


If I'm not mistaken, I am the wheelbuilder in question here.

It's important to note that I was speaking about the rims that we use, which are not FarSports rims. Though they look roughly similar, my experience with the rims that we use should not be considered applicable to any other rims (as I explained when I was asked originally). Only the people who made your rims can tell you for sure what tension limits to use. Therefore, my statement can not be considered "important data" as regards this discussion.

There is absolutely no use in the world for putting 150-160kgf on spokes. You are approaching (or exceeding) the ultimate strength of a lot of spokes at this tension, you run a high risk of deforming or breaking hub flanges, normal spoke wrenches are useless at this kind of tension - you would need to use hex drive from the inside, and most importantly you are doing all of this for zero benefit.

The rims we use have been tested with excessive spoke tension. Spokes break before the rims do. The absolute limit of what the rim could take is well in excess of your 150-160 number. The safety margin I reference is far bigger than what you are assuming.

Zipp has a maximum spoke tension on their rims of 100kgf. I think if 130 being under tensioned had any validity at all, then you would just see massive epidemic failures of their wheels, which you simply do not.

Beyond the point where the spokes are prevented from going slack, increased spoke tension has no benefit in increased wheel stiffness. This has been tested and documented many times. http://www.sheldonbrown.com/rinard/wheel/index.htm

Our forthcoming new rims, which are being produced by the same rim maker as the open molds we have used but are not open mold rims (we own the mold), are designed to be built with the same 130kgf max as we have successfully been building with for several years and many many many hundreds of rims.


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PostPosted: Mon Mar 18, 2013 2:01 pm 
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fdegrove wrote:
Hi,

Quote:
Besides, the wheel's stiffness doesn't depend on spoke tension.


Which begs the question, what does spoke tension influence if not stiffness?

Ciao, ;)


Well, I think Dave has summed it up pretty well in the previous post. :thumbup: Higher tension can prevent NDS spokes from going totally slack but doesn't contribute to better stiffness.


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PostPosted: Mon Mar 18, 2013 2:08 pm 
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when I asked Farsports what spoke tension numbers they use for reference when they build the 38mm clincher rims, the max number they provided was 135 for drive side. in my actual build, the LBS never actually exceeded 125 on an individual spoke in getting the wheels rounded.

dave, i didn't intend to introduce your comments out of context, nor mean to imply anything about the materials you use, only wanted provide an input as to max spoke tension being used by people who know what they're doing out in the field. i apologize if it was misconstrued or otherwise used inappropriately.


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PostPosted: Mon Mar 18, 2013 2:51 pm 
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I just wanted to emphasize that what works for one rim might not work for another. Zipp has a prominently low recommended spoke tension, which obviously works in their wheels. We build with more tension on our rims, and it works for us. No problem at all with referencing my statement, it's just important that it not be taken to mean that I think all carbon rims can or should be built with that tension. Our rims are different than what's being discussed here, so the tension that I use isn't a transferable measure.


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PostPosted: Mon Mar 18, 2013 3:20 pm 
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Location: Santa Cruz, California, USA
LOW PROFILE carbon clinchers are no lighter than low profile aluminium clinchers. But if you want aero rims, carbon is the way to go. 40mm deep aluminium rims are very heavy while deeper profile carbon clinchers are not that heavy.

Carbon clinchers are getting better at dealing with brake heat. I used my farsports rims on the steepest most technical descent that we race down in NorCal and they did ok. But I'm relatively light and I know how to descend. Your mileage may vary.

I do not use them for training because I sometimes descend even steeper and more technical descents, and because the wheels aero advantage is not important in training. I'm riding to get faster, not to look "pro".

For me tubulars are not practical for long road races with spotty support. One of my favorite races is two days of at least six hours each, where half of the course has no support. In this race flatting does not mean you are out of the race so being able to repair a puncture in a reasonable time is important. I do not have enough experience at changing tubular tires to be willing to do it on the side of the road after 5 hours of racing. And carrying a tubular would negate the weight advantage.

I do have a set of tubular wheels for races where they're appropriate.


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PostPosted: Mon Mar 18, 2013 6:48 pm 
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very interesting. So if i don't race i guess there is no point. they do look better though.

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PostPosted: Mon Mar 18, 2013 11:21 pm 
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Back to high spoke tension - at 100kg of max spoke tension what is spoke tension with tire inflitated on 9 bar? Ok if 100kg are on DS maby they are on 90kg - but spokes on NDS ? if they have 40-60kg before tire inflitated - some can go to zero tension.
maby this is topic for wheelbuilding

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Posted: Mon Mar 18, 2013 11:21 pm 


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PostPosted: Tue Mar 19, 2013 9:25 pm 
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wrcompositi wrote:
Liggero wrote:
150-160 would be a better mark (not for the spoke tension, but as the maximum load a decent rim should resist). Thing is that you can´t make magic, it will be either too heavy compared to alu or too weak for less spokes. 382g for a 38 carbon clincher it's very on the weak side I think. But if you leave the spokes with low tension or you just don't brake like pefendreu, there will be no issues, but it won't be stiff enough and not braking it's a extreme sport. I've seen deformed carbon clincher flanges from any brand, you name it; reynolds, enve, shimano, campagnolo, asian rims... I don't think these rims are better than enve. But I may be wrong of course.


Farsports claims max tension of 300kgf for theirs rims(http://www.wheelsfar.com/38mm-clincher-wheels1250g-30g-p-220.html). Besides, the wheel's stiffness doesn't depend on spoke tension.



Well, they are strung up 100F/140R, the wheel is rated higher...

Anywho, anybody running these wheels in clincher/tubular?

I have a set of Zipp 303 FC Tubulars...I train mostly on them during the race season because of the hassle swapping between my 50m deep V carbon wheels that are like 10mm narrower. Just a hassle/pain to swap and re-set the brakes everytime.

So, my thought it switch to a set of clinchers like those in the link above, use them for training same depth and near dimensions...so hopefully the brake track/width adjustment of the calipers wouldn't be needed, or much less time spent, so I can easily train and swap easily for the race to the Zipps. Also, in case of a flat, much easier to repair while training, which has happened, I basically had no brakes on the one wheel because trying to adjust the caliper/adjustment available was too much going from 28mm Width to a 19mm Width wheel. Not good with 40mph descents at times and hills, could still stop, but a bit unnerving and had to think way ahead...haha.


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