Bicycle Mechanics - can a dropped chain break spokes?

something weird happened today - maybe not so weird.

downshifted on a hill and dropped a chain on the rear wheel. normally wouldn't be a big deal, but when I pulled over I found that four spokes had snapped.

did some fishing around and realized that there is no "dork disc" on my back wheel. i think my LBS removed it when they installed my custom-built wheel.

is it true that a missing dork-disc will lead to spoke breakage when dropping a chain? if so then I think the LBS owes me four spokes and a wheel truing.

thanks & sorry if this is too obvious!

I think it's possible.

the dork disc isn't necessary if the bike's rear derailer is setup properly, as it's supposed to prevent the RD from jamming into the spokes.
Usually your RD will get destroyed before your spokes break from a jammed chain.

chain falling off to the inside, between the wheel and cassette would indicate that someone didn't setup the RD properly.

thanks. I'm sure the LBS will argue that the disc isn't necessary if the RD is set up properly and that's why they left it off, but they are also the last ones to touch it. from what I can tell the RD is OK, didn't hit the spokes.

I've seen spokes break from a chain that vibrated off (probably in part due to a poorly adjusted limit screw, which itself might have vibrated loose) during a downhill. Instant flat on his rear tire. So yeah, it's not necessary if your bike is properly adjusted and you don't ride aggressive bumpy downhills, but it can't hurt either. With a nice wheel, I definitely wouldn't take a chance.

I've dropped my chain into the spokes (proper adjustment, but really worn derailleur) and it shaved several spokes down to about 1/2 their original thickness. I can believe that several spokes would break.

Been there, done that.

If it can get in the spokes - it can break 'em.

yes it could happen but quite frankly its possible it could happen if the dork disk is on there too. The LBS can easily say that you were riding and doing something you shouldn't have been doing that caused to the chain to come off so it's your fault. How exactly did the chain come off? Did you shift to the large cog and it just jumped over? that to me would be an improperly adjusted RD and if they were the ones who adjusted it, that definately adds to the issue of who is at fault?

NEvermind, just read that you were going downhill so you most likely weren't in the large cog. Post a pic for us so we can see where they broke. The dork disk isn't there to prevent all spoke breakage. i'm looking at a friends bike right now that has one onthere and it's only a smidge bigger than her large cog. It's clearly only designed to keep the chain from going in there on a shift. I know some dork discs are much larger than the largest cog, but that is still no guarantee it will protect the wheel in all circumstances.

I've never had the dork disc and i have no idea when it happened, but some of the nice black spokes on my new Rol Race SLs are scraped up, I don't think it'll reelly be an issue as it appears to be just the paint, but as a racer who obsessively tweaks their bike, I can say that it happens to the best of us. Better to not walk into your LBS all pissed off and demanding some spokes and a true, go talk to the head mechanic, and let him know what happened, at worst a couple of spokes and a true will cost you like what $30? Its more important to have a good relationship with the head mech. at your LBS, I can't even begin to count the number of times I've been in over my head in a repair, or needed a tool that I didn't have where my LBSs head mech. Hasn't been there to help me out, and he's never charged me for one of those "yep im a dumbass because i forgot to do something minor that messed up everything" moments. You never know when you'll need a quick favor or He/she will be buying a new bike and swapping out parts that you might want or something.

Lack of dork disc doesn't cause spokes to break; something getting tangled in the spokes causes spokes to break. If it's a broken or dropped chain in your spokes, then yes, that'll do it. Whether a dork disc would have helped you in this instance, I don't know.

I leave my dork discs on, but maybe I'm more comfortable in my dorkiness than most. Most things that a dork disc protects your spokes against are prevented by keeping your bike in good repair and adjustment, though. A dork disc will usually keep an out-of-adjustment rear derailleur (and its chain) out of your spokes. Often, but not always, in a crash, it will do the same. A dork disc will never keep a squirrel or a stick or an errant broken chain out of your spokes, though.

yeah i shifted to the large cog and it jumped over (while going uphill).

seems like an appropriately sized disc would catch a jumping chain. otherwise it feels like I'm at risk of a wheel blowing up anytime.

The derailleur can be perfectly adjusted, but if the hanger is slightly bent it won't matter.

Also, anyone who insists a "properly adjusted" rear derailleur can't be made to over-shift hasn't worked on bikes for long. Cheap derailleurs flex so badly that if you set up the low limit to where you can't manually (moving the derailleur with your hand while while pedaling) over-shift, when you shift with the cable, the derailleur will not climb up onto the largest cog. This is one reason cheap bikes are so hard to work on: they defy doing things by the book.

But, I guess now I'll have to have people who don't want a dork disc sign a waiver.....:p

On one of my bikes the chain wedging in there took out the entire drive side. The three or four spokes that didn't actually snap were badly mauled and bent. I've had dork discs on all my bikes other than the single speed bikes (where there's easily enough room for the chain to fall in and not do anything bad) since that time.

Custom built wheels don't come with guard discs. And in fact not all that many bikes come with them anymore. So the LBS isn't liable for replacing your spokes. And the general trend is to not use the discs anyway so even if they rebuilt a wheel for you I would suspect that in today's market you'd have to request that the dork disc be re-installed on the wheel to ensure that it goes there.

As for not needing them on a properley adjusted bike? There is that. But it is also the nature of things to go OUT of adjustment for a large number of reasons. And the dork disc is there to save our behind for those times that we don't quite catch things before they go bad or for the times where a little stick or stone lifts the chain up and over into the "Valley of Destruction".

yeah they said that the custom wheel didn't come with a spoke protector. my beef was that the previous wheel DID have a spoke protector and they didn't keep it on there.

and I think that you are right that the spokes that didn't snap are damaged as well.

hardto believe lots of bikes don't come with spoke protectors...in fact Cannondale had a recall last year for lack of such: http://www.cpsc.gov/cpscpub/prerel/prhtml09/09155.html

To answer your question yes a dropped chain to the inside between cassette and spokes can result in broken and or damaged spokes.
As far as who is to blame hard one, I will always say it comes down to operator making sure bike is in good mechanical condition before rides this includes adjustments and making sure parts are in good condition worn parts can cause a chain to drop even if adjustments look good, so in that case if the shop just tuned your bike it may be hard to convince them to fix it with out charge, they may give you a break on labor who knows.
Good luck and hope it gets fixed soon.

So now you're one of the converted. Sad that it took this sort of damage to join the club.

Still, as we've discussed here the trend is to not use them. The very name "dork disc" shows that there's a current machismo attitude about not having them. It's like someone bragging that they don't need fire or theft insurance on their house.... until the unexpected happens. *shugs*

The guys that say that if the systems are kept adjsuted correctly are quite right. But I've got too many other hobbies and activities, not to mention lots of bikes to keep straight, to be checking my shifting to ensure that it won't overshift into the spokes on a weekly or even monthly basis. I ride 'em until the shifting starts to wander and then tune them. If I had the time and fewer hobbies so that I COULD go over all my bikes on a monthly basis perhaps I'd be one of the guys posting that they are not needed other than for the mountain bike used for trail riding. But I'm not so the bikes don't see that sort of attention. So I proudly and prominently mount my dork discs and ride with peace of mind.

The spoke protector is more to protect the spokes from an over-shifted chain than from the RD cage.
I'm not currently using one, which does put me at some risk for a problem, even if I conscientiously maintain adjustments. Things happen.

The disc does a good job of protecting the spokes. Don't leave home without it. The dorks are the ones who take it off so that they will look cool.

something weird happened today - maybe not so weird.

downshifted on a hill and dropped a chain on the rear wheel. normally wouldn't be a big deal, but when I pulled over I found that four spokes had snapped.

did some fishing around and realized that there is no "dork disc" on my back wheel. i think my LBS removed it when they installed my custom-built wheel.

is it true that a missing dork-disc will lead to spoke breakage when dropping a chain? if so then I think the LBS owes me four spokes and a wheel truing.

thanks & sorry if this is too obvious!

More then possible. I lent a bike to an intern for the summer, he managed to break 7 of 8 spokes on the drive side by dropping the chain into the spokes. He even managed to break 7 of 8 Alpine III spokes which are 2.3mm heads which are much more robust than other spokes. I'm not even sure how he dropped the chain into the spokes considering that I ride this bike a lot and never had any hint of over-shifting.

The real sad part is that the build was my first use of DT Alpine III spokes and was over 10 trouble free years old.


I think it's possible.

the dork disc isn't necessary if the bike's rear derailer is setup properly, as it's supposed to prevent the RD from jamming into the spokes.
Usually your RD will get destroyed before your spokes break from a jammed chain.

chain falling off to the inside, between the wheel and cassette would indicate that someone didn't setup the RD properly.

Not necessarily. No derailer damage. Just a bunch of broken spokes.

Same here. No derraileur damage. Just a totally wiped out drive side. And like you it wasn't even me riding it at the time. I was trying to sell the bike and it was a fellow that took it for a test ride that did it. He was as apoligetic as hell and I all but had to assure him that it wasn't his fault.

For the record this particular old school Italian frame racer was my first and only foray into the "dork discs aren't cool" school of thought. It was also my last as a result of having to rebuild that wheel.

People who buy quality components, take care of their **** and maintain it will never need dork discs.

whatever, operator.

so the LBS took one look at my shredded spokes and apologized profusely for not installing a pie plate with the custom wheel.

looks like a bent derailleur hanger was the proximate cause of the dropped chain, so they'll split the repair with me somehow. thanks all for your helpful advice.

People who buy quality components, take care of their **** and maintain it will never need dork discs.
You KNOW that is not true!

You KNOW that is not true!
prove it

The disc does a good job of protecting the spokes. Don't leave home without it. The dorks are the ones who take it off so that they will look cool.

On my Big Dummy the plastic dork disk self destructed in only about 4 months and started causing drag on the freehub and cassette so that the freehub did not want to freewheel freely. One of the mounting prongs failed and the disc moved off center in relation to the cassette. This caused the chain lower run to tighten while freewheeling with wierd results. IMO makers need to come up with better designs or materials for the disk as the current ones can cause their own problems.

Quite possible the disc was damaged during wheel assembly but the disc did fail and if it had of jammed harder between the cassette and spokes I suspect that the chain could have damaged the derailleur.