20 spokes enough for a cyclocross disc wheel?

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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blantonator
Posts: 115
Joined: Sat Oct 23, 2010 8:36 pm

by blantonator

I have a set of 20/28 50mm carbon tubulars I use for cross and was thinking about moving to a disc specific frame, but would like to keep the rims. I'm not worried about relacing the 28 spoke rear rim to a disc hub, but what about the 20 spoke front wheel? Is 20 spokes on a 50mm carbon rim enough to handle braking forces of a cross bike?

by Weenie


fat tire
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Joined: Wed Mar 19, 2008 6:54 pm

by fat tire

A carbon rim not made for disc brakes will not work. The stopping power is so great that the spokes will rip through the carbon.

Frans
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by Frans

Great, please post the link to the empirical tests which yeilded this result.

Does this objective test explain why Reynolds just released a disc version of the Assault? http://www.cyclingnews.com/features/pho ... 012/191430

Is this what WW has become in the last year I've been away?

BTW, as well, here's HED's disc carbon wheel: http://www.cyclingnews.com/features/pho ... 012/191417 I'm too old to stare at my screen that close to count the spokes but both wheels appear to have 24.

fat tire
Posts: 354
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by fat tire

I did not say carbon can not be used for a disc wheel. Please learn to read Frans. I said carbon rims not made for disc will not work. They will not last long. That does not mean it can not be done if the spoke bed is reinforced. His rim is clearly made for a rim brake. I have spoken specifically with a couple manufactures about this. Plus I saw some of the early testing with standard carbon rims. It did not go well.

I have carbon Bontrager mtb wheels with disc hubs. I do realize it is possible.

Is this what WW has come to? Pasting pics of wheels with no clue of what was done to the carbon rim. With your logic all carbon rims are the same because they are round and made of carbon.

Frans
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by Frans

Your implied arguement that each and every carbon rim on the planet must be taken back to the drawing-board and have the spoke-holes beefed up before it can be released to the market is a lazy overgeneralization and you know it. 12+ years ago when discs were catching on in MTB, regular rims were laced, crossed, to disc hubs b/c that's all there was on the market. I'm not talking pre-built, just local builders/shops.

The Reynolds wheel is operable as both disc and rim braked, the weight isn't far off the road weight and they're not advertised as "new and beefed up" or "disc ready" or "weight limit of x" any other claims like that is an indication it's a bog standard Assault rim re-purposed. Maybe they need to make this point.

If you have knowledge that Reynolds did anything at all to the Assault rim besides lace it, crossed, to a disc hub then please share.

fat tire
Posts: 354
Joined: Wed Mar 19, 2008 6:54 pm

by fat tire

@blan if you decide to do it. Please post pics in a month or so after you have used the wheels. I guess that is the only way to settle this debate.

@ Frans I will not name companies, but like I said I have knowledge that off the shelf rims failed in a short time after being laced to a disc hub. Also the two companies are not going to post data that their rims laced up to disc hubs failed. Why would they? If you have inside info then great.

The drawing board does not have to be big. Do not worry. The wheels only need al or more carbon where the spoke nipples/ washer meet. That does not increase weight much.

Im done with this topic. Blan have at it. Please update. I will be curiously watching.

blantonator
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Joined: Sat Oct 23, 2010 8:36 pm

by blantonator

my question was more out of curiosity. I have no plans of doing this right now.

Briscoelab
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Joined: Thu Jan 26, 2006 6:01 pm

by Briscoelab

Rim strength would be 100% fine. Reynolds and HED aren't doing anything special on their new wheels to make them "disc brake strengthened".

However, I would be a bit hesitant on the 20hole rim. Not from strength stand point, but from a stiffness during braking standpoint.

Disc brakes put a lot of stress on the spokes and I'd personally feel better with a 24 to 28 hole build from that standpoint. But, again, stresses the wheel will see in a cx race are lower than those in a MTB race.... so it might be acceptable.

People have been using carbon road wheels in disc builds (to mount MTB tubulars) for years already with little issue.

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euan
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by euan

what disc hubs are available in 20 and 24?
"Step forward the climber and all those who worship at the altar of lightness" - R. Millar

Colin
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Joined: Mon Mar 02, 2009 4:50 am

by Colin

If you can find any, Hope makes the Hope Pro 3 in 24h disc.

adallaserra
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Joined: Fri Jan 25, 2013 3:37 pm

by adallaserra

20H-24H-disc-carbon-rims.jpg
Wheelset alone.


20H-disc-carbon-rims.jpg
20H/24H two crossed carbon wheelset on Planet X UncleJohn (soon to be replaced with Dengfu's FM059)


Well... I've just done it. All good so far. Hopefully I'll survive to tell the tale as I'm mainly riding road and the braking torsion is more.
I've put Ashima Di2 discs on there to remind myself I shouldn't go too heavy on the levers!

As a note, the wheelset came to 1510g without discs - 1670g with. They are both 2Xed and feel super stiff. Not too much flex on braking either, but again I havent ploughed the levers in yet (or plan to much).

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ms6073
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by ms6073

fat tire wrote:A carbon rim not made for disc brakes will not work. The stopping power is so great that the spokes will rip through the carbon.
While Jeremy Powers at Rapha-Focus has been racing on Easton's 50mm track rims, you might want to let Jaime Driscol, Tim Johnson, and Ryan Trebon of the Cannondale-Cyclocrossworld pro team know as they have been competing all season on carbon disc wheels built with SRAM Rise 60 disc hubs laced 24/24 to Zipp 303 Firecrest tubular rims.
Michael - The Anaerobic Threshold is neither...

Frans
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Joined: Wed Jan 25, 2006 8:32 pm
Location: Bow of a Farr 40

by Frans

ms6073 wrote:
fat tire wrote:A carbon rim not made for disc brakes will not work. The stopping power is so great that the spokes will rip through the carbon.
While Jeremy Powers at Rapha-Focus has been racing on Easton's 50mm track rims, you might want to let Jaime Driscol, Tim Johnson, and Ryan Trebon of the Cannondale-Cyclocrossworld pro team know as they have been competing all season on carbon disc wheels built with SRAM Rise 60 disc hubs laced 24/24 to Zipp 303 Firecrest tubular rims.

I think we hammered poor ol' fat tyre enough on this subject:

http://www.tweekscycles.com/Product.do? ... tAodVGIArg" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Only 20 spokes and they're 29ers so you could use them on a cross bike! So the answer is yes.

I remember when I was 16 people used to make unfounded comments like that re: GEL280 rims and super lightweight exotica that "no one could ride without it spontaneously exploding".

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ms6073
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Location: Houston, Texas

by ms6073

After a full season of racing on both Saturday and Sunday of every weekend since October, I think my 3-sets of 28-hole, semi-light carbon disc brake wheelsets built with Chinese 50mm carbon tubular rim brake rims have held up well and I have yet to see any indication of the spokes pulling the internal spoke nipples through the carbon.

Frans wrote:Easton EC90 XC
Only 20 spokes and they're 29ers so you could use them on a cross bike! So the answer is yes.

Actually that wheelset might not be the best example as the Easton rims are UST/Tubeless, disc specific and as such, have no brake track as well as a slightly reinforced spoke bed. 8)
Michael - The Anaerobic Threshold is neither...

fernandoj
Posts: 1
Joined: Mon Apr 15, 2013 4:27 pm

by fernandoj

Two years late but I hope you like it.

http://fernandoj.wordpress.com/2013/11/ ... clo-cross/

by Weenie


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