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PostPosted: Tue Feb 12, 2013 9:35 pm 
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Joined: Fri Jun 03, 2011 9:11 pm
Posts: 188
Hey team,

I just broke my third spoke in a raw on equal wheels. I cannot identify the cause though, making just assumptions and leading nowhere. Any ideas?

I am currently 80kg (176.4 lb), 1.9m (6.16 ft) tall and ride a 6.4kg Orbea Orca on a variety of terrains from flat to 21% slope.

First failure came from my 2011 rear Easton EC90 Aero wheel, when a DS spoke broke during a steep incline. Wheelset has been purchased new from the local importer and I had only put around 600Km on it. Replaced the spoke on my wheel builder with a CX-Ray, no problems so far.

Second failure was on the rear wheel of a custom set put together from 20mm carbon tubular rims (Planet-X branded), BHS hubs and Sapim CX-Rays laced on a 20/24, radial front, 2XDS, radial NDS patern. The set came as light as 1040gr. A NDS spoke broke right out of the hub hole during a ridiculous slow cadence, almost no power resume after a break at the bakery shop. Worth mentioning that I managed to ride home for about 50km with one spoke less. CX-Ray was replaced using the same builder who originally built them up.

Third incident occurred today on the same custom wheelset, this time a spoke broke while cruising at around 25Km/h out of the front wheel, right out of the hub hole.

Took the wheelset to a different builder this time, he said he needs some time to inspect and will get back to me. I have just mounted my spare Racing Zeros on the bike but I am so into tubulars, I really cannot stand seeing the bike with alloy clinchers.

So is it me? Am I too heavy? Am I riding weird (I think not)?, is it my builder? Any thoughts are welcome. I am in the process of purchasing a 38mm deep carbon tubs with 24/28 spoke count and brass nipples, will do any good?

Thanks for reading and sharing thoughts...

_________________
Trek SpeedConcept 9.9 Project One, Orbea Orca Gold 6430gr, Orbea Aqua, Tommasini Tecno, FM-066SL 6480gr, Kinesis RaceLight T2, Trek Superfly 100, Orbea Alma 29, Trek Session 88, KTM EXC-250


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PostPosted: Tue Feb 12, 2013 9:53 pm 
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Joined: Fri Feb 08, 2013 9:30 pm
Posts: 12
Hi,

Since you have had 3 spoke failure I would draw the conclusion that it´s something about how you ride the bike that´s causing this. It´s not easy to tell though. The mechanichs behind a spoke that snaps is that for each wheel revolution the spoke gets streched and pressed. All these revolutions will eventually cause metal fatigue to the spoke.
I hope you will find a solution to this.


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Posted: Tue Feb 12, 2013 9:53 pm 


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PostPosted: Tue Feb 12, 2013 10:34 pm 
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Joined: Thu Jun 09, 2011 4:10 pm
Posts: 305
Similar height and weight here.

I've had no luck with Easton wheels/spokes. The older ones ripped the nipples through the rims. Had some EA90's that popped spokes sitting in my office at work multiple times after complete rebuilds. Eventually narrowed it down to a 2.5mile 7% descent I take pretty routinely. The speeds and cross-gusts for whatever reason are hard on the spokes - and it seemed to me that Easton runs high tensions, which tend to be problematic.

I've had good luck with shimano wheels since then (though I swear the rear feels a bit noodly at times), and would always go with a higher spoke count at my weight, especially in the rear - I'd think a 24 / 28 setup would be adequate.


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PostPosted: Wed Feb 13, 2013 11:03 pm 
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in the industry

Joined: Sat May 12, 2012 7:25 pm
Posts: 1482
Location: Glermsford, Suffolk U.K
Spokes snap because they fatigue. Either the spokes that have gone are low tension ones (i.e the wheel was not evenly tensioned) and it those spoke that would fatigue more quickly or more likely there is insufficent spokes for your riding style.

Also the hub flange spacing/flange diameter have an important role to play in determining a suitable spoke count. Some hub has poor flange seperation. Combine that with a low spoke count and flexy CX-ray spokes and you may have a recipe for spoke failure. Your riding style will infulence this alot too.

IF you break spokes then more thicker spokes are advisable. Also use a hub that give a better bracing angle and don't stand up and roack the bike when applying high torque to the rear wheel. Stiffer rims will also help.

I am the same weight and height and my regular wheels are DT Swiss RR415's 28F/28R on Miche hubs (they the best hubs for crap weather riding, cheap and very durable) and Sapim Laser spokes. No spoke breakages. Although in Suffolk there are no really steep climbs. I do not ride out of the saddle and even if I do I keep the bike upright which helps I think a bit.

The same rims and spokes though built on Novatec A291/F482 hubs are even stiffer as these hubs give better bracing angles compared to Miche hubs. So the choice of hub is very important, don't neglet it.

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www.thecycleclinic.co.uk


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