Forum menu
Why would a spoke.....
 

[Closed] Why would a spoke....

 DT78
Posts: 10066
Free Member
Topic starter
 
[#1672133]

just snap all of a sudden? Of all things it was on the wall climb whilst cranking round one of those tight switch backs.

Went with a real bang and snapped at the middle of the spoke.

Wheel build is about a year old (proII/721) and had no problems with it, wasn't buckled etc...

Top guys at skyline cycles sorted it, but just wondering what might have caused it to fail. I could understand if I was jumping or something


 
Posted : 04/06/2010 10:13 am
Posts: 41395
Free Member
 

It'll have been weakened for whatever reason. It's not only the obvious things like jumps that put stress on your wheels - when climbing, a lot of your weight is on the back wheel which is also dealing with pedalling forces etc.


 
Posted : 04/06/2010 10:15 am
Posts: 6886
Free Member
 

I'm no wheel guru but could it have been over tensioned?


 
Posted : 04/06/2010 10:16 am
Posts: 35040
Full Member
 

Dunno, probably just waiting to happen, or a weak spot, something like that. I think spokes are cold drawn, so the normal fatigue spots are where it's been worked, so at the bend or the thread, but it doesn't stop them from just "going" once in a while


 
Posted : 04/06/2010 10:17 am
Posts: 39735
Free Member
 

my wheels are currently away for warrenty because ive had 5 or 6 spokes snap in the middle of spokes as you describe.

factory wheels ! - ive built wheels for 10 years for a shop downhill/xc/road/lightweight and never had this issue - so i lodged a complaint and they took em back to rebuild em.


 
Posted : 04/06/2010 10:19 am
Posts: 0
Free Member
 

Snapping in the middle is unusual - it's likely to have either been damaged at some point (stick/rock type thing) or just a manufacturing defect.


 
Posted : 04/06/2010 10:40 am
Posts: 9
Free Member
 

Possible impact damage in the past?


 
Posted : 04/06/2010 10:47 am
Posts: 6985
Free Member
 

most likely your missus cut it, thinking it was a brake pipe.

call the police and have her charged with attempted murder.


 
Posted : 04/06/2010 11:00 am
Posts: 0
Full Member
 

I had a spoke break near the top of Kipps at GT last month. That was annoying in that it was the worst place/time for it to happen on that ride but would have been much worse had it happened similarly on my next planned ride which was Mount Keen. I have been advised that once a spoke breaks the wheel strength is fatally compromised and a rebuild with a new rim is needed. I'm being a bit cautious until I get that sorted.


 
Posted : 04/06/2010 11:04 am
Posts: 41395
Free Member
 

Kunstler - Member
I have been advised that once a spoke breaks the wheel strength is fatally compromised and a rebuild with a new rim is needed.

That's utter BS! You can often keep riding on a wheel missing a spoke, and usually they repair up fine (depending on damage obviously).


 
Posted : 04/06/2010 11:07 am
Posts: 39735
Free Member
 

depends on the wheel cynic al

if it was a stock wheel that came on a factory bike with cheap spokes - and was snapping from fatigue at shoulders id reccomend replacement - often youd find your self chasing broken spokes round a wheel !

well built wheels with dts dont generally do this


 
Posted : 04/06/2010 11:11 am
Posts: 39735
Free Member
 


 
Posted : 04/06/2010 11:12 am
Posts: 3422
Free Member
 

I have been advised that once a spoke breaks the wheel strength is fatally compromised and a rebuild with a new rim is needed.

Really? I need to get the wheels on all four of my bikes rebuilt pronto then, i've obviously been on borrowed time all these years! ๐Ÿ˜‰


 
Posted : 04/06/2010 11:12 am
Posts: 41395
Free Member
 

Sure - after 3 spokes go for no apparent reaons I's say rebuild - the post refers to one spoke though.


 
Posted : 04/06/2010 11:12 am
Posts: 0
Free Member
 

I just take spoke breakage as an act of god. Given the abuse wheels take I'm surprised they don't fall to bits in hours. With a disc braked wheel you can still ride with several broken spokes, there's plenty of redundancy - I'd just replace any broken ones ASAP. Having said that, I can't remember the last time I broke a spoke...


 
Posted : 04/06/2010 11:13 am
Posts: 4789
Free Member
 

one large cause of spoke breakage is uneven tension between spokes


 
Posted : 04/06/2010 11:44 am
Posts: 0
Full Member
 

trail_rat - that sounds very much like my situation. It's an xtc which has everything else upgraded but the original wheel is four years old. Several spokes have been replaced now - two more broke during the last replacement.


 
Posted : 04/06/2010 11:46 am
 DT78
Posts: 10066
Free Member
Topic starter
 

Wasn't a factory set - LBS build, I think most likely is that it could have been weakened as suggested. Very odd though first time I've had a spoke go in all the years I've been riding.

I actually continued riding w2 and got skyline to fix it afterwards. I didn't die, but the wheel most definitely was buckled by the end of the ride it did true up fine.

Irritatingly the nipple is inside the rim now rattling around.


 
Posted : 04/06/2010 12:01 pm
Posts: 659
Free Member
 

"With a disc braked wheel you can still ride with several broken spokes, there's plenty of redundancy "

I do not think that is really a good idea, rim braked wheel maybe with extreme caution,
all the braking force in a disc wheel is via the spokes...

The odd spoke may break, if your wheel breaks 3 or more spokes best rebuild it unless you have a good idea why its happening.


 
Posted : 04/06/2010 2:02 pm
Posts: 39735
Free Member
 

I do not think that is really a good idea, rim braked wheel maybe with extreme caution,
all the braking force in a disc wheel is via the spokes...

can i suggest you think about that statement.


 
Posted : 04/06/2010 2:04 pm
Posts: 659
Free Member
 

yep, thought about it , the braking force is the hub being stopped by the disk. Hub needs to transmit braking force to tyre via rim and spokes.

Rim brake - force from rim to tyre .

Is there some other explanation ?


 
Posted : 04/06/2010 2:21 pm
Posts: 41395
Free Member
 

Spokes are involved in dealing with the stresses of rim braking.


 
Posted : 04/06/2010 2:22 pm
Posts: 39735
Free Member
 

yep, thought about it , the braking force is the hub being stopped by the disk. Hub needs to transmit braking force to tyre via rim and spokes.

Rim brake - force from rim to tyre .

for the love of god your not an engineer - please say your not !


 
Posted : 04/06/2010 2:24 pm
Posts: 659
Free Member
 

why not explain if what I said was so wrong?

yes spokes are involved in the stresses of rim braking , but I think they are far more important in disc wheels


 
Posted : 04/06/2010 2:30 pm
Posts: 659
Free Member
 

suppose you build a radially laced front wheel with a disc hub and rim brake rim.

what brake would you feel safest with that wheel ?


 
Posted : 04/06/2010 2:40 pm
Posts: 39735
Free Member
 

what your implying is that the hub would continue to rotate irrespective of rim slowing down.

all a rim is , is a giant disk ...


 
Posted : 04/06/2010 2:42 pm
Posts: 41395
Free Member
 

all the braking force in a disc wheel is via the spokes...

We're just being pedantic about that statement, I suppose the answer is that with a rim brake there are no rotating* forces on the spokes.

*yeah sounds wrong but YKWIM


 
Posted : 04/06/2010 2:44 pm
Posts: 39735
Free Member
 

i thought stw existed solely to be pedantic and pick up on minor points ....

i see where your coming from - it is a less force going back to hub but its a force none the less

simple fact of the matter is - rim brakes are not really possible with a snapped spoke due to wonky rim - disk brakes are due to redundant contingency of spokes in 32/36 spokes


 
Posted : 04/06/2010 2:47 pm
Posts: 659
Free Member
 

yes ok i get your point with a rim braked wheel , the braking spokes stop the hub , but do you see my point? the torque issues with disc hubs ?


 
Posted : 04/06/2010 2:52 pm
Posts: 39735
Free Member
 

yep - dont worry i was just being pedantic ๐Ÿ˜‰


 
Posted : 04/06/2010 2:53 pm
Posts: 659
Free Member
 

ok ok I think we are on a similar track , I forgot about the wonky rim redundancy ,


 
Posted : 04/06/2010 2:54 pm
Posts: 41395
Free Member
 

All friends in the end! ๐Ÿ˜€


 
Posted : 04/06/2010 3:15 pm