What is your "dork disc" actually for? What happens if you remove it? 

One time my derailleur wasn’t adjusted well, and my chain fell into my spokes. I thought, “perhaps I shouldn’t have removed my dork disk?” Then I snapped out of it and remembered that I’m no dork! Haven’t looked back since! Stay classy my mtb brethren

I found this one out the hard way one day. About 200m into a ride down the road on my mountain bike, my chain was thrown into the spokes and I got the result I think you were trying to recreate. I was rolling downhill at a fairly high speed so there was a lot of energy at play -- it was violent. The wheel basically exploded. Three spokes got torn out of the rim and pushed across into spokes on the other side, bending those and pulling them out of the rim as well. The wheel buckled, jammed in my chainstay and that was all she wrote. Still don't ride with a dork disc.

As others have noted this is called a "spoke protector" in official vernacular. You should post an update with a look at what happened to the spokes on the Diamondback. As a former mechanic, I've seen many wheel failures due this kind of damage. Even minor nicks will cause failure due to the high tension spokes are under (think cutting a loose string with a knife vs tight string)

HI Seth, the biggest factor in having a catastrophic chain suck event is how the direction of the outward bound spokes on the back wheel are pointing. If the outward bound spokes are going forward it will cause the chain to bounce and not get sucked in. If the outward spokes are directed backwards, they will actually pull the chain in deeper. A wise bike mechanic, wheel building wizard told me the secret!

I believe it the cheap plastic that makes this “dorky”. this is a great opportunity to have this item made in aluminum, engineered to be light weight, and anodized black, etc.

Took off my "dork disk" immediately after buying my trek emonda. Then I wrapped my chain. I was on a big descent and traveling fast. Did a little backpedal to line up for an upcoming curve and my right heel must have pushed the chain off the cassette and into the spokes. It locked up the back wheel and wedged the chain so badly I had to have somebody drive out to rescue me. Skidded the tire off almost completely. I didn't lay it down on the pavement but I got lucky. No derailer damage. I have a picture of the ~100 foot line of rubber left on the pavement. The disk went back on. I don't give a s**t what others say now - it's my bike, my wallet, and my skin!

This is how I broke my first bike back in the 90s. My derailer went into the spokes so violently that it actually bent the frame at the attachment point. My limits were not even out of whack! I was a Junior bike mechanic at a local shop at the time, and all the wise older mechanics shook their heads when I showed up without a dork disk on my GT Avalanche. They said I should spend the $7 for a new one, but I was way too cool for that. A week later I was late to work because the rear derailer went into the spokes and turned into a pretzel. 17 year old me learned an important lessons that day, and the wise older mechanics got a good laugh watching the last few hundred feet of my walk of shame.

Hi ! Bike tech here. The dork disc is mainly there to protect the spokes from the chain, but it wont prevent to derailleur to be sucked up in the wheel. Also the main reason the derailleur gets sucked up in the wheel isnt a badly adjusted Low limit screw, its a bent hanger. A bent hanger will put the lowest point of the cage a lot closer to the spokes and when you shift into low gears to cage is getting caught by the spokes way before the chain can go over the cassette. In this situation, the dork disc is completely useless, this is why we so often remove it.

Leave the dork disc on if it's a bike for a client! For you, your friend, your family it's good to take off. If you're in a workplace setting don't take off the disc! You're liable for removing safety equipment. I have that shirt 😉

The test needs to be done with the chain under a lot higher load. I had my chain dump behind the cassette on a moderate climb and the chain jammed hard, putting gouges in the spokes in the process. The bike had to be carried home only for the chain to easily come off once the thru axle was loosened. The freehub body had come loose from the main hub, causing the indexing to get out of whack.

I've been building my own wheels since about '03. The disc is something I wish someone had improved. When you're building a wheel with ~$4 spokes, it's nice to know that something is there to protect your investment from a poor tuneup.

i really like how true and natural you are, this video looked complicated for you to do but in a way its still helpful for beginners like me. love your content

It's actually called a spoke protector, with good reason. A bike shop took the one off my MTB years ago and were adamant that they would never refit a "dork disk". I regretted that last year when I was bike packing a 1200km off-road trail over 3 weeks. The bike took a hammering each day, the limits went out of adjustment, and a couple of times the chain got stuck between the spokes and cassette. There was no catastrophic failure like you were trying to create, but each time there was some damage to the spokes. Eventually some damaged spokes started breaking. I had spares but very difficult to fix on the trail, over 50km from the nearest bike shop over rough trail. Will now always have the "spoke protector" fitted.

I think it's only a legal requirement in the US (and maybe EU?) - every "good" bike I've bought in the UK hasn't come with a dork disc, which includes Shimano Deore and SRAM Eagle. My Girlfriend's Trek Marlin came with one, but came off pretty easy with some cutters :D

Pro tip: If you want to strap your bike to a treadmill, consider tying it down like you would a motorcycle in the bed of a pickup. The concept is exactly the same. Tie it down by the handlebar, one strap for each side of the bike, and completely independent of each other. Do the same for the rear of the bike, but because it doesn't pivot like the fork, you can use one long strap and the bike won't move. The problem arose from tying the bike down behind the pivot point, which allowed the handlebar, fork, and wheel/tire assembly to wobble. I never really thought about removing them. It's clear plastic, it isn't in the way of or bothering anything or anybody, so why waste the time it would take to remove it? Yeah, it looks like MAYBE, if one was unfamiliar with how to remove their rear wheel and how to access the disc without cutting it up, it MIGHT take as much as 10 minutes, but in reality, probably closer to five. It wouldn't really be all that difficult to remove. I don't know, whatever floats one's boat I suppose. As it ages, and being clear plastic, it's going to haze over and get dirty and scratched, but the rest of the bike's finish is going to get dirty, scratched, greasy , chipped, etc. I don't remove the chainguard from the front either, but as ugly as they were, we all used to remove our chainguard from our bikes because they really were dorky. Once they were off, we used to mangle and twist them so they couldn't be put back on by our fathers when they got pissed at us for taking them off. But the kinds of guards they have now, I don't mind them in the least.

This was a good video! I'm not an extreme rider, but I've owned a ton of different bikes over the last 20 years. I've always taken the spoke protector off when it is yellowed or already chipped or broken. I've never had a problem as a result of removing one.

Usually you are pedaling up a hill, sometimes pretty hard, when you shift the chain off the cassette looking for a lower gear. Without the dork disk this can wedge the chain pretty far into spokes and even the hub. Then it can be very difficult to remove the chain and it can damage the spokes. This is a pretty different scenario than your experiment demonstrates. I think the purpose of the dork disk is to lessen spoke damage if this happens.

It needs to become a fashion part so that everyone wants to have one installed :) Gotta make one out of carbon fiber or even kevlar and rename it to "superfancydorkdisc"! 🤓

I actually made one for my new DT wheel, because the chain left pretty significant marks on the hub and I wasn't even pedaling that hard and I stopped right away. I designed it much wider, so the chain can't physically go further. Then printed on a 3D printer.

Well, I felt on my skin the importance of a dork disk. It happened when I shifted up a gear at the wrong time while climbing a pretty big hill. The chain get stucked that bad it took me more than one hour to unstuck it and be back on track. I had no tools on me and all I could use was some sticks and my bare hands. That happened 20km away from nearest city and at Some point I considered calling one friend to come and pick me up with the car. So yes, in some situation a dork disc can make a huge difference

The wheel is one of the most expensive parts to replace on a bike, so I really feel like even if it's just protecting your spokes from grinding against the chain, it still pays for itself.

What I think is that I want to see premium versions of these disks, something presentable for a good bike, maybe some anodized aluminum or something

Great video, I hated explaining to people why I have to put this on every new bike, just to take it off when they're sold... I worked mechanic, and I'd say these are unnecessary in most bikes, other then very low end ones. in very low end system, the derailleurs have so much give, they can easily be bumped or forced and get the chain between the cassette and wheel.. but there's usually a big enough gap, that the plastic might help a bit. But I think the biggest problem is that, this plastic thing usually brakes apart and is just wiggling there after a couple of months. which is where it tends to get caught the most in my experience.

My Target $160 Schwinn bike's rear derailer snapped at the neck, and the broke off majority of the derailer caught in the spokes and braked the rear wheel. In the process the plastic dork disc was shattered. I fixed the bike by installing a new Rear Derailer. No damage to the wheel. Bike works great with just replacing the rear derailer. I did not replace the dork disc though.

I think what really happened is in both simulations with the dork disk off was, as your weight was not actually on the bike, that did not force the wheel to continue spinning and causing damage. If you pay attention around 7:30, the wheel locks itself but in reality that would hardly be the case.

I'll say this: "If it ain't broken don't fix it".Meaning that it's there for a reason.From my experience it is very usefull,and practical.

Awesome presentation...im now commencing to intall all 15 dork disks on my bike collection..thanks for the awesome content and the heads up

Like you discovered, I've seen plenty of dork discs fail to do anything useful in the event of derailment. Might as well take it off. But as others have stated, never take them off for clients, due to liability issues. Take them off for yourself.

you can experience spoke damage, I had a chain slip over on an eagle drivetrain on a punchy climb. Upon inspection by removing the cassette I found a few bent and scarred spokes, I rode for about a year before one of the spokes finally broke. I still don't use dork disks; but there is real risks.

I can remember multiple occasions when the chain fell into the spokes and caused catastrophic failure on my bike. Multiple derailleurs were trashed, several wheel spokes broken on different occasions, and once, the chain got caught and bent in half, rendering it as well as the derailleur junk. Maybe it looks dorky, but it beats breaking down during a ride and having to do repairs.

These discs were made of metal in the 1930s, and were a vital piece of safety equipment for derailleurs like the Super Champion Osgear, where the chain is shifted onto the next sprocket by a pivoting fork. The fork is under strong spring pressure, and if unchecked, will will be forced into the spokes. Normally, the correctly adjusted gear cable, connected to the derailleur by a pinch bolt, restrains the derailleur, but if the cable were to break or to slip from the grip of the pinch bolt, then the fork will fly into the spokes without the protection of the metal (usually aluminium) disc. Perhaps, if the disc were made of metal instead of flimsy plastic, it could serve a practical purpose. I imagine, though, that cyclists who are more image-conscious than self-confident would still object to them.

Thanks for trying to show us, I also had a very bad time on a downhill as a kid... I had to change my rear derailleur, but not because of the indicident. It was because I was a dumb kid and used my bike as trash. But I got a considerable amount of damage to remember the accident and to respect my bike and treat her properly...

“It can be melted down into aluminum wheel chairs, cans, and lawn darts” amazing how he never wastes materials

As other commentators have said, that “dork disc” is a spoke protector. The chain can be much harder metal than the spokes. An adult riding over rough ground can put a lot of force through the drive train. When the chain goes between the cassette and the spokes it can cut into the spokes like a saw. That can severely weaken the spokes, leading to the whole wheel eventually failing. That little disc is there to take the hit so that the wheel doesn’t get destroyed.

Very nicely put together video and very entertaining as well. Thanks for posting this.

I’ve been riding for a long time, since 1990. I had an incident like you, however the dork disk had a split in it and the chain got sucked up and damaged the derailleur. This was the only time that happened to me, but the circumstances seem to be similar, lots of speed and a very bumpy trail.

i actually want to get a metal dork disc, that way pieces of it don't break off when it gets old and brittle spoke protectors that were used on vintage bikes, the chrome ones, looked really awesome and often came with cool designs like logos punched into them or fancy patterns this was before everything was plastic and people made sure that every bike component made the bike look good in my opinion, no amount of ''coolness'' is worth risking crashing or destroying a bike over, especially for something as trivial as a round disc

When I raced BMX in the 90's, we all used to run metal dork discs to help amplify the sound of the freewheel

Today I learned that my wife’s bike needed a dork disc 2 months ago. The derailleur was sucked up into the spokes and we couldn’t figure out why. Thanks for this video!

I have broken a derailleur because I had removed the disc. No, I won’t ride without it. It’s nice to see you doing Phil-Level things in a controlled environment. :)

This happened to me only once in two decades. Destroyed my road bike rear wheel. Bought a replacement wheel set. Tried to sell the old front wheel. Found a lot of front wheels on sale on eBay, but not rear wheels. Then I realized this problem was more common than I expected!

One of my first rides on my brand new $4200 mountain bike, this happened. I was on a steep, granny ring climb, the chain jumped between the cassette and spokes and turned the derailleur into a pretzel in about 0.5 seconds. It was so wound up in there I couldn't get it loose by hand. So, with the multi-tool, I started loosening every little bolt on the rear der. Turns out, one of the pulleys had so much tension on it, that once it was loose enough, a couple parts let loose with such velocity, that it sounded like bullets tearing through the leaves and branches in the woods. If it had hit me, hospital trip for sure. Anyway, the spokes were a bit nicked, but still worked, I had to buy a new der. and I avoided losing an eye, so a 'fun' and 'educational' experience.

I worked at a bike rental, and between the thousands of bikes I had to maintain there, and the thousands of miles I've personally covered, I have seen broken spokes, shattered derailleurs, and chains so badly bound between the rear hub and cluster that they could not be retrieved without removing the cluster. Whether those incidents included the plastic disc or not, I cannot say. My head mechanic had a habit of ripping them off whenever they became even slightly damaged, so I'm sure many of those failures occurred when discs were absent.

Great video thanks for the share. Personally I’ve never had any problems with a chain coming off the sprocket and going into the wheel but then again I only ride on the road and my bikes have always been properly maintained and my first bikes in the 60s never had gears but I’ve always left the dork disc on like any other “safety” device.

I've had the chain come off that way before and tbh the worst part that would have been remedied by having a dork disc was getting the chain back out so I could pedal again. Without one, depending on the design of your cassette, it can get jammed in there is a way that is difficult to pull back out (and makes you wonder how it got there in the first place)

If you are trying to shift into your biggest cog, you're probably not going very fast. And if the derailleur isn't bent, it's pretty much impossible for it to get caught in the spokes

Might be a good idea on front wheel drive recumbent bikes such as a Cruzbike. I rarely use the largest cog, so haven't used a spoke protector in years. Years ago, the spoke protector was made of heavy chromed steel.

the high and low adjust screws are there for the limits for a proper adjustment so the chain doesn't fly off the sprokets

Great video. In my experience(manhattan bike shop), the most common thing that tangles up rear derailleurs is debris/obstruction: most commonly the lowly street curb. I have literally 0 experience with the MTB market, but the shop I work at in NYC replaces 3 or 4 rear mechs/hangers a month from the pushed-into-the-spokes type catastrophe. The dork disk is often present and intact for such jobs.

If the chain drops behind the cassette under tension, (i.e. on a steep climb when you really wish you had one lower gear) it can really thrash the spokes right where they insert into the hub. It weakens the spokes at the point where they normally break. Nothing catastrophic has ever happened to me, but I've ended up rebuilding several wheels because of it when a spoke or two broke sometime down the road. I had more trouble with the old 3x9 setups, where the cassette was smaller. Modern larger cassettes tend to have clearance between the cassette spider and hub that wasn't there on the older, smaller cassettes with full steel cogs. I've seen a few jammed tight enough that they were very difficult to get free, but only when the chain was pulled in by someone standing on the pedals.

First thing I ever did on a mountain bike was stick it in lowest and shear the rear axle retention clips off the frame, bend the rear rim and rip the valvestem off. Too many years pushing a little MX36 one speed I guess. The dork-disk's *entire purpose* is to keep the cheaper parallelogram shifters from digging into the spokes directly. That's it. It stops kids and fools from allowing the duplex from damaging the spokes and causing an unsafe ride. It is the single largest example of a "warranty void if removed" device you will ever see.

Great video and appreciate the work you put into it. Have you or will you do one on the front chain ring leg saver?

I've seen wheels with the spokes ripped apart from this happening, the dork disc could have saved a lot of them, I'm actually going to make myself an aluminium dork disc like I see on old road bikes to save me money in the long run on wheels

Last week I managed to rip off the derailleur including the hanger in a split second. It was freshly build up for the showroom in the store. 1. You have to ride, your weight gives the forward momentum. 2. You need to have a wide range derailleur with a long cage… actually a dork disc wouldn’t help in this scenario, because it’s the bottom part of the cage that catches a spoke… 👍

One thing I've learned from repairing is that most the time I see issues is when the derailleur hanger is bend in and no dork disc, try bending in the derailleur hanger on the cheap bike and then try your experiment might have the outcome your looking for!

My experience says that these Mainly prevent spoke damage from overshifting. I've definitely had the occasional overshift event over the years and it creates small scratches/gouges on the spokes. I had a spoke break once due to this. The spoke then grabbed the derailuer... Carnage ensued. No crashes, though... No idea how this would cause a crash. You're going to be pretty slow any time you're using that gear.

On my last hybrid bike, the dork disc disintegrated and eventually my chain did end up off the cassette. It didn't do much damage the first time, but it happened a few times over a year and eventually chewed through some spokes. The biggest problem with the dork disc is that it's made of such cheap plastic it often breaks off the hub and spins freely, prompting the owner to just snip it off.

Hi Seth, with the underground pushing the wheel the spokes push on the chain - kind of from the inside out. If you're actually pedalling only then will the chain be pulled into the tightening gap.(outside-in). And if you pedal hard like e.g. on a steep climb then the chain might very well get locked with exactly that force, Cheers :)

Here in Germany, a lot of the bike paths are cobblestones. Once I was biking home, shortly after replacing my rear wheel. The dork disk had been removed and not replaced at the shop. I was going fairly fast, shifting up into top gear, when I hit some bumpy cobblestones. The chain bounced up and off the gears, falling between them and the spokes. And it cut through four or five spokes like a chainsaw. Luckily, it was not too long a walk home.

So, I was riding my bike down the trail and my chain went over into my spokes and then it ruined my wife's tread mill. You rock Seth. I love your channel.

What you didn't address is the damage to the heads of the spokes as the spinning wheel grinds them against the non-moving chain. After a few of those incidents, the spokes will begin failing, either when the heads break off or at the 90° bend where the spoke exits the hub flange.

Personally I think that they call it a dork disk for a reason. It's just like taking reflectors off, even if it doesn't make a difference, it just feels right.

This video was very helpful. Thanks.

Props for publishing the video despite inconclusive results!

I respect the fact that you used your good and expensive bike because the cheap bike didn’t have good results. Great content Seth!

I actually ended up buying a "dork disk" - I've replaced my rear wheel twice on my old bike, perhaps 'cause I carry too much with it. But I never bothered replacing the original "dork disk" because I thought I didn't need it. Then when coming home from a commute one day, my derailleur freaked out randomly, and wedged my chain firmly between freewheel hub and spokes. The rear wheel locked up completely, and I couldn't free the chain. Had to carry heavy 20 KG bike home on shoulders with a walk of shame. Not fun. Could only be freed by unscrewing the freewheel hub. So now I have a dork disk to stop that from happening again, even though I keep my bike maintained and it's not done that since. Good thing I wasn't far from home, or carrying anything.

Although bikes & wheels I've bought don't come with the Dork Disc, bikes I've had as a kid had them. I remember these a lot thicker, stiffer & would turn yellow after a couple of years. They would not let chain go between sprocket & spokes. The treadmill fiasco got me to subscribe. Also love the 10 hacks videos, although I ride road bikes.

I have experienced the issue you wanted to recreate more than once, and I think what you were lacking was your full weight on the bike making the chain get stuck closer to the center, where it might get caught up in a way that's hard to get out without dismounting the cassette.

“I bought MY treadmill..” “Amy is not going to be happy about that”

Seth, you're testing a 35 lb bike just riding on a treadmill and the rear wheel ends up hopping around as the chain causes havoc. in real life, there is a 150 lb rider and a ton of momentum on that bike, so a lot more energy and potential for damage. that weight on top of the rear wheel also keeps that wheel on the ground spinning until the considerably larger momentum eventually gets slowed down by crushing metal and friction. in short, I think the real life scenario involves way more energy. also, who knows what can happen if you get that happening at speed, you could lose control of the bike even if the damage isn't that bad. all that being said, we took off our dork disks too.

Check the j bend area of your spokes for damage where the chain just chewed into them. This means later on they will more likely fail and break. Your shifting components are not the only things that can be damaged.

Hell, back in the late 60's before "spoke guards" were common, the Campagnolo rear derailleur on my Puch failed (limiter tab the range screw pushed against broke), sending the lower arm into the rear spokes. The result? (a) 3 or 4 spokes destroyed and (b) the bike stopped much faster than my then 170# body so I went over the handlebars and ended up with a major case of road rash. The new wheel got a stamped aluminum spoke guard. 50+ years later I'm still riding and quite happy leaving the disk in place on my current bike!

Great stuff ! After years of cycling i definitely have fewer problems on bikes i have fitted with this device .

Hey seth! Could have someone machine a custom dork disc out of metal, like aluminum or titanium for you to test? I would personally rock one of those if they existed!

As a kid, while riding an old 5 speed through the woods something got kicked up into the derailleur jockey wheels, it locked up the chain in the derailleur, the derailleur folded to the left and into the spokes, almost instantly it removed about 10 spokes and the wheel was done for the day. The bike had a tiny tin dork disc that really didn't extend beyond the largest sprocket. The older bikes had HUGE discs, some as big as 9" or so and made from chrome plated steel. Those would have stopped the wheel from getting damage, but would not have stopped the derailleur from being ripped apart. I have had bikes toss the chain and it get caught behind the freewheel, both with and without the disc installed, rarely was it just a matter of lifting the chain back in place, but it was on much older bikes in the 70's. Many times the chain was what suffered the most, with the occasional marred up spoke or two. Years later, I tend to leave them in place, and put them back if missing if the bike is being ridden off pavement. On the road, it depends on the bike.

I noticed that on the last Shimano cassette I purchased that they have added a handful of little nubs (like the one on my old FUSO's seat stay to hold the chain for wheel removal) to the spoke side of the innermost cog in order to catch the chain in case of an over shift. Seems like a good idea and looks way better than a dork disc.

I have repaired a lot of bikes for friends and family over the years and these plastic discs make absolutely no difference. It's usually the old, dirt-packed, rotting drivetrains that implode when the chain is overshifting into the spokes. Though the concept of this unloved part is actually not too bad, but wrongly executed. For it to work manufacturers should include it in the cassette (like an extra non-toothed cog, slightly larger than the lowest gear). Included firmly on the cassette so it won't rattle around, maybe with some rad color accent or even color-customizability (wow I should patent this lol) But it must be a part of the cassette if it's supposed to stop the chain overshifting. If you catch it after it's already dropped into the spokes, it does not matter if there's a dork disk or not. If the chain and spokes are full of dirt and scream friction, it will grab and go funny.

Been mountain biking for 33 years. Although I have had the chain get jammed into the spokes quite significantly, I have never had a catastrophic failure in this manner. Disclaimer: out of the fifty of so bikes I've had, I've never left the plastic disc on the bike.

Bike given for repair. The mechanic removed this plastic disc. He said I didn't need it because the gears were perfectly adjusted. A few months later, the chain did slip behind the gears. A couple of spokes were broken, the chain was damaged and the derailleur hanger was also bent.

I wonder if the bike's power system was under a load (like when you were actually biking) there would have been more adverse consequences? Kudos for taking this demonstration on!

This has only happened to me a hand full of times in 30 plus years of riding without a dork disk, where the chain has gotten caught between the spokes and the cassette. The worst case for me was the chain got so wedged in-between that the chain cut 2 of the spokes and I had to remove the cassette to get the chain out (no dork disk). Best case is that the chain just pulls out, but I have always have had damage to the spokes and it a judgment call on whether to replace them of not. The dork disk is sacrificial gear that helps protect the spokes from damage when the chain gets caught.

My experience without a DORK disc and a misadjusted lower limit stop screw resulted in severely damaged spokes. So much so that the rear wheel needed to be rebuilt. Granted this was on a road bike before mountain bikes were even a thing. A Schwinn Paramount with Campy Nuovo Record derailleur. But I was a teenager, what did I know. And yes I don't ride with a DORK disc on any of my chain drive bikes.

I never knew the dork disk was required by law! I’ve had a few instances of the chain jumping into the spokes on older bikes. The one time it happened on a modern bike was when I bent my hangar and still had to ride out.

When adjusting the rear derailleur, I alway hand shift the derailleur to the top cog and double check if the limit screw is adjusted properly. Sometimes it's a fine line.

I'm an aerospace structural design engineer and I leave mine on. it has a purpose; it's extremely light, and the material is chosen specifically to have it fail before the other components fail. this will save yourself some $ in lieu of replacing other more expensive, metallic components. additionally, this will hopefully allow you to figure out what happened so you can adjust your rear and get back on the road or trail so you can get home without being stuck in the middle of nowhere. Obviously, most people take it off thanks to the misnomer "dork disc" and wanting to either be "cool" or at least have their bike look more attractive. Smart design and safety is cooler to me, but hey we still have those riders that think helmets look dumb so to each their own.

Would've liked a look at the spokes because I've seen spokes get ground almost all the way through having worked in a bikeshop for almost 10 years

I have always removed the "pie plate" from my bikes. That being said, as things would have it. I had just finished rebuilding my bike with a new frame. I had scored a a new GT Zaskar frame that was left over when they did the bankruptcy thing. A stick flipped up into the spokes and tore the rear derailleur hanger off. I was able to find another hanger and replace it plus the mangled XT derailleur.

Once while working as a Bike tech, we had to fix a Trek Slash that a local races at the bike park. Where he had been doing a stage and while pedaling on flat, His chain went behind his cassette. Because he had continued to pedal through it, the chain then sheared all of the J spokes that run on that side of the hub. Snapped the chain, derailleur hanger, and bent the derailleur cage. Causing him to crash, he was okay.

Please try that bike out on your trails! I've had a jammed chain like that once, with a dork disk in place. Ended up with a severely twisted chain.

The treadmill is missing the part where the rear wheel is hammering on a bumpy trail and the tensioner on the derailleur goes slack enough to throw a chain that's not under much tension. Spoke guard is there for that kind of thing. Just an extra bit of insurance to not catch spokes and possibly taco a wheel in the process.

I rode my last bike (Hybrid mountain bike) to and from work for years with little issues apart from maybe a puncture or two. Last month I was heading home and as I bumped up the curb I felt the bike jarring and trying to buckaroo me off. After stopping I saw a mangled mess between my spokes and realised it wasn't just the chain but my derailleur as well. The force of it even though at low speed even managed to Snap the hanger on the frame which was welded on, meaning the whole bike was scrap. I think that it's not speed that makes the difference here but flexing of the chain in a up and down motion. Although it sucks that this bike I had been riding for the better part of 4 years is gone, it gave me the excuse to purchase my first real mountain bike since I was a kid and can finally ride trails again.

I've had a few road bikes come with these and I always wondered what they were for. I think it's funny watching you carefully take it off your bike when in the past I've definitely just ripped them in half to get them off 🤣

The disk is there to protect the user, not the bike. It prevents the chain from getting caught in a moving rear wheel and bypassing the free wheel/hub - which causes the chain to pull on the chain ring… essentially making the bike a fixie. An inexperienced rider may not be able to stop pedaling, especially if they were clipped in or strapped in. Even when the rider can get their feet off the pedal, the crank arms will keep on turning, attacking the rider’s legs until the rear wheel stops turning; as seen in Seth’s video (where the pedal eats into the back of his leg - thankfully he’s wearing jeans). It is a safety device meant for people who will not take into account skill/equipment/terrain/speed/etc… a worry-free device. Take it off when the rider is ready for all that.

I jumped off a set of stairs on a super cheap specialized, and when I landed it bucked the chain off and then got sucked into the wheel snapping the derailed and a few spokes. That bike was my ride home so that was fun.

I've never had my derailer get sucked up, but I did have my chain come off of the casette or the front gear before. Definitely makes for a surprising way to pause a ride

My 1970's Schwinn Varsity had two "dork discs". It also had a small metal one aside the smallest sprockets on the cassette. If your derailleur is misadjusted, it will prevent the chain from exiting the cassette and jamming between the cassette and the frame.

A few years ago I came up with an idea to replace the dork disk with something that would actually prevent the chain from falling into the spokes. It basically is a ramped dork disk. The ramp stops even with the highest gear so the chain would just slide down the ramp until it hit the sprocket. It could even be snapped in place or zip tied to the spokes. Was going to use some Carbon/Kevlar cloth to make one but never got around to doing it. Of coarse it would only work for the cassette that I have on the bike but I thought it would be a fun experiment, none the less.

When I was a teenager, I rode a Raleigh Gran Prix 10 speed. I replaced my freewheel and had the big, chrome, metal spoke protector removed. I had yet to adjust my rear derailleur limit screws. A friend wanted to see how the new gearing felt and immediately shifted to the lowest cog. The chain jammed between the freewheel and spokes and ripped my Simplex derailleur from the hanger.

I see another purpose for the thing: it does protect your cassette on one side from collecting debris. Yes, it is likely to become rather dirty with the time, and is not that well suited for cleaning, but with it missing, you would allow sand and dirt, even objects like branches to go into your cogs faster.

I got a used Gravity Bullseye Monster fatbike, and I got it adjusted pretty good (I thought). I took it on it's first real ride, and I whacked the derailleur on a log, bending the derailleur hanger. Later when I shifted back to 1st gear, it shifted past off the sprocket, and got wedged real good. My buddies I was riding with helped me get it fixed, and ended up having to destroy the dork disk to get the chain un wedged. I think the dork disk did it's job, since the bike rode fine after everything was bent back into shape, and readjusted on the trail.