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2014-04-13 6:12 PM

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Subject: Broken Bike Spoke
I was 58km through my 60km bike ride this morning and I heard a snap. I looked down and one of the spokes on my back wheel had snapped.

Just wondering what causes something like that to snap?


2014-04-13 6:29 PM
in reply to: todd89


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Subject: RE: Broken Bike Spoke
It happens, many reasons. Get the spoke replaced and make sure the wheel is true. Pray you don't snap another one. If you blow a spoke right after its replaced, the rim is probably ready for retirement.
2014-04-13 7:48 PM
in reply to: ziggie204

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Subject: RE: Broken Bike Spoke
I blew my first spoke ever 3/4 of the way into my Sprint tri yesterday. Scared me pretty good!! I ended up finishing, and even hit 37.9 mph on a downhill afterwards. It scratched up the inside of my front forks pretty good. :-(

My bike guru helped me replace the spoke and nipple, and true it up. He works for beer. Nice! He said I'm a real cyclist now. :-)
2014-04-13 8:29 PM
in reply to: todd89

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Subject: RE: Broken Bike Spoke

A bicycle wheel is really an extreme mechanical device in terms of strength to weight ratio.  The spoke are tensioned above the yield limit and go thousand of tensioning-detensioning cycles per mile  This fatigues the spoke material causing it to become brittle and ultimately break.  Bicycle wheels are truly an engineering marvel. But they are right at the limit of breaking all the time.

I would guess that this is a rear wheel and has 24 or fewer spokes.  You probably ride these wheels all the time.  And you weigh more than 175 lbs.   And you have owned the wheels 2 or more years.  Congratulations, you just wore out a spoke.  It happens..  

One thing you can do to improve the life of the spokes is to be sure that the spokes are equally tensioned to the correct tension specification.  You can get an iPhone app for $5 that is very accurate.  When you true the wheel, you should be able to achieve >0.02mm variation radially and laterally and tensions all within 6% of specification if the rim itself is true.   Spokes experience greater fatigue if they are too loose or too tight.  You want them all bearing equal load.  You want them not to ever go completely slack under load either.  The spoke at the bottom should remain in tension under the normal vertical load of the rider. 

If you want to never break another spoke,  get a set of 36 spoke 3 cross wheels with 2-1.8-2 mm double butted spokes.  These are not particularly aero and not light but they will be more durable than a 24 spoke racing wheel.  There is just more load margin in each spoke than in a 24 spoke racing wheel.

TW

2014-04-13 10:29 PM
in reply to: todd89

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Subject: RE: Broken Bike Spoke
Thanks for the replies

I had thought that it may have snapped due to being well used. The wheels are now over 3 years old.

How much does it usually cost to get the spokes replaced?
2014-04-14 12:21 AM
in reply to: todd89

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Subject: RE: Broken Bike Spoke

Non-drive side is cheaper than drive side (must remove cassette).  10.00 bucks + cost of spoke/nipple would be about right.  If you 'pluck' your spokes like a guitar string and compare their "note", you'll be surprised how close you can get a wheel to even tension without using any gadgets. 

Buy a cheap wheel and practice relacing it.  Few things in cycling are more satisfying than riding wheels you built yourself.



2014-04-14 12:51 AM
in reply to: todd89

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Subject: RE: Broken Bike Spoke
Many things can cause the spoke to break. Impact, fatigue, uneven spoke tension (which is by far the most common btw).

When replacing the spoke, make sure the wheel is trued and that the spoke tension is checked. It must be even and correct or you will break many more spokes.

Good news is that it's usually less than $25 for the whole thing… spokes are quite inexpensive and it's not labor intensive.
2014-04-14 7:18 AM
in reply to: todd89

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Subject: RE: Broken Bike Spoke
Originally posted by todd89

How much does it usually cost to get the spokes replaced?


Two Killian's Reds at my house. :-)
2014-04-14 8:13 AM
in reply to: todd89

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Subject: RE: Broken Bike Spoke
Originally posted by todd89

I was 58km through my 60km bike ride this morning and I heard a snap. I looked down and one of the spokes on my back wheel had snapped.

Just wondering what causes something like that to snap?


All kinds of things can cause a spoke to go. We might be able to zero in better if you give us more info.

How much do you weight?
How many/type of spokes are on each wheel?
rim size?(21mm, 23, 25,28,..)
Was it a rear spoke? (which Side)
do you ride on bad roads?
How much power do you put out?
When did it snap?(going up hill, right after a pot hole,...)
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