"Dork Disk"
 

Howdy folks
Was riding my old mtn bike in the forest preserve today and the yellowed, brittle old "dork disk" finally crumbled to pieces and basically fell off. Now, I know dork disks are deeply uncool in these parts, but apart from that, is it worth my while to replace it? If I go on and ride without it, am I risking some sort of catastrophic failure where the chain skips off the biggest sprocket and gets entangled in the spokes, locking up the wheel and sending me over the handlebars? Thanks for your advice as always.

If your rear derailleur set screws are properly adjusted, you have almost no worry of your chain wrapping up in your wheel, which is why lots of people remove them. That and they're ugly.

If the rear wheel locks up you won’t go over the bars.

Do you need one on a mountain bike? It depends how you shift. If you end up forcing downshifts and overstressing the drivetrain a chain plate can pull apart and/or you can pull the rear derailleur off and it is possible to drive it into the spokes, more so with a steel frame without a separate hanger.

If it is too catastrophic, it may not help.

But if you anticipate and have good shifting technique, you don’t need one.

John

For me, I don't like dork disks for aesthetic reasons. They are only useful for people who don't maintain their bike or know how to shift. After cleaning my bikes, I check the alignmenet. Every 500 miles, I check the limit screws to make sure the chain can't go over the biggest cog into the wheel.

For all the people who want to keep the dork disk because they think it's safer, the OP just threw a wrench into that logic... The Op's DORK DISC is what failed! What if it broke a spoke?! I never kept a dork disc on long enough to fail, but now I have another reason to remove them.

I've seen said disks that were just slightly larger than the diameter of the largest cog, black colored and somewhat discreet. I'm assuming the disk occupied enough space so the chain wouldn't fall into the hub.

Or the owner over lubed their chain and road in the wet conditions causing dirt to fly off onto the dork disk???

Anyone who's worked in a shop long enough has seen the effects of a rear der in the wheel. the disc won't stop it from happening in some situations but I've seen it help. My kids have them on their bikes and I knew that the oldest had bent her hanger on a MTB ride when I heard the der rubbing on the disc which did keep it out of the spokes.
On the other hand I don't have a wheel on any of my bikes that has one.

Depends on Bike
 

I think it depends on the type of bike and year it was made. On Vintage bikes I think they look awesome. Kept clean and shiny they add to look of the bike. But the plastic ones once they've yellowed are plain ugly. As far as spacing, in my exp. especially with vintage bikes they are there to provide protection. The "dork disc" was not flat and provided protection from overshifting which is very easy to do on friction shifting.

A shiny, 40 year old "dork disk", reflectors and "turkey levers" or anything else that would have been ripped off and trashed being still intact makes a survivor bike a little more special IMHO.

^^^ Yes. Some dork disks, oops I mean pie plates, will never break... and removing them would wreck the look of the bike.

https://cimg0.ibsrv.net/gimg/bikefor...66c17dbf9a.jpg

When I rebuild bikes(usually from the 70's and 80's) I always put spoke protectors on them, I also put reflectors on the spokes, pedals, and front and rear on the frame. The bike exchange requires them on all of our donation and sale bikes. Throw the chain into the spokes and you will ruin about half of the spokes on that wheel. Ride at night and you can get a ticket if you don't have reflectors and lights. A bike is almost invisible at night without them and anytime you hit a car or it hits you you loose big time, says someone who spent 2 weeks in hospital with 2 broken ribs, a punctured lung , and a bruised kidney after colliding with a car. there is nothing uncool about safety.

Did a 3 day ride on the GAP trail. At the end of the second day my buddy's 35 year old bike threw the last of his already busted up dork disc. At the start of the third day he jammed the chain in between the spokes and freewheel when pumping up a steep hill in traffic. Luckily some guy stopped with a truck full of tools or I think we would still be on the side of the road trying to get that chain free. People from the Pittsburgh area are super nice.

I don't have a single bike with a dork disc, but honestly have to wonder why sometimes.

I just replaced the dork disk on a Bridgestone, someone got smart removed and then munched the chain torching all of the elbow out spokes. New spokes and now Dork on.

https://cimg0.ibsrv.net/gimg/bikefor...96dbf50240.jpg

Sounds better than Dork off.

Why not just use lights? Rather than relying on a car's headlights to illuminate the reflectors, just use your own lights so the driver can see you BEFORE their headlights reach you? When I ride at night, I've got a rear light, a front light, and small lights shoes and helmet. The batteries last 17 hours and are charged after every ride.

+1 I always recommend replacement of spoke protectors on bikes with rear derailleurs because it can help reduce or eliminate damage to spokes from the chain in the event the rear derailleur moves too far when downshifting to the lowest gear (shifting to the largest cog). On a mountain bike the rear derailleur can easily get knocked out of alignment if it brushes against something during an off-road trail ride. Any bike with a rear derailleur that is knocked over on it's drive side can suffer a bent derailleur hanger. A strong gust of wind can push a bicycle over resulting in a bent hanger. Finally, if the derailleur low limit gets out of adjustment it can allow the chain to skip past the largest cog and move toward the chain causing damage to the spokes. Once the derailleur is out of alignment or mis-adjusted all it takes is downshifting into the lowest gear to shove the chain into the spokes. If a spoke protector is there it may reduce or eliminate damage to the spokes.

As far as reflectors, I always recommend replacement of missing reflectors on the front and rear of the bike as well as reflectors in the spokes front and rear. These items are required to be mounted on all new bicycles by the federal CPSC and for good reason. I can see not putting them on a vintage bike that never had them that will never be rode at night or in bad weather.

I don't have dork discs on my bikes, however, check carefully the adjustment of the RD.

I had to remove the cassette once as the chain fell between it and the spokes and I couldn't remove it by hand. Fortunately it happened on my front door.

They're ugly, they make noise, some of them are crap, but they serve a function.

I don't have idiot dork discs on my bikes. I have spoke protectors. A rare but occasional missed shift can score the outer spokes and they will eventually break from fatigue. After an overhaul years ago I forgot the Spoke Protector and at a busy intersection I missed a shift and dropped my chain. A few rides latter a spoke broke. When I went to replace it that 8 others had been cut so I replaced them all.
The limit screws were properly adjusted.

These two statements are mutually exclusive. The limit screw prevents the derailleur from going beyond the largest cog. If it is set correctly, the derailleur cannot physically get the chain over the cog.

Another thing about spoke protectors , (lets not be hatters and use some slur to name them eh?)

You have to use different kinds dependent on the spoke count and whether you have a freewheel or free hub. There are different sizes depending on the largest cog and also different materials used. On entry level bike boom models you had chrome steel (along with steel rims), on higher end vintage bikes you had Aluminum disks. You might also see disks with aluminum centers and plastic on the outside. These all have a round hole in the center that fits over the freewheel hub.

Another type has a larger hole in the center with at least 2 types of attachment. These can be used on freewheels or freehubs. the first type has tabs that attach directly to the hub flange. a second type has tabs that slide over the individual spokes. These Spoke protectors are different depending on whether the wheel has 32 or 36 spokes.

On really extreme wheels with ridiculously low spoke counts I have never seen protectors. They may exist but the bike shops remove them before sale.

Actually, I get most of my reflectors and spoke protectors from a high end bike shop. They never use them. The kind of customers they get probably don't do their own repairs so when they trash a wheel with the chain in the spokes they just go in to the shop and buy a new one. when you are spending thousands on a bicycle you can afford it and for the bike shop it is guaranteed business.

Yellowed plastic I discard. Chrome beauties on vintage bikes I keep.
https://cimg9.ibsrv.net/gimg/bikefor...ca4c301216.jpg
https://cimg0.ibsrv.net/gimg/bikefor...463693d91d.jpg

At least for modern bikes they are designed as trash they frequently cause more problems then they are worth (plenty of builders coming to me say "warranty, warranty:" and I pull of the plastic disc and problem goes away). If you take care of your bike and make sure your derailleur is properly adjusted it won't go into the spokes and if you hanger or derailleurs bends or breaks that little cheap plastic disk ain't gonna do much to help you. A bike should be well maintained anyway and if you are not doing that you will have many more problems that a plastic disc cannot solve. A well maintained bike is a happy bike and a happy bike is a happy rider and a happy rider is all right with me : )

Some of the vintage ones however can be quite nice as browngw has shown us. That Sekine one actually gets my heart a tiny flutter.

There was one time I was coasting along slowly checking out a then new construction area. I started to backpedal a little to set things up to trackstand for a longer look, and in the process, the chain decided it wanted a closer look at the hub flange. It was long enough ago I don't remember whether I'd hit a bump at the wrong instant, or if my chain had just gone slack from losing engagement with the chainrings, but however thins unfoded, it severely gouged out 8 spokes.

My limit screws were set correctly.

When the chain comes off the chainrings, there's enough slack that the rear derailleur doesn't track the rear sprockets closely as normal. In this event, even with the limit screw set correctly, the chain can easily walk off the sprocket.

That incident was the last straw, having already replaced the 8 spokes after a similar incident a few years prior. The spoke protector I'd found had a nice ledge on it, so of the chain goes past the large sprocket, it rides up on the ledge rather than down into the gap behind the freewheel.

Luckily these derailment events always seemed to happen to me at low speeds - I've never had one happen when the chain getting caught up and locking up the rear wheel would cause a real safety issue. Since putting in a third-eye chain watcher and the spoke protector, nearly 20 years ago, I haven't had a problem since.

Would be curious to know who is doing your work and what derailleurs you have?

I'm not cool enough to ride without a dork disk.

As long as they are not yellowed or broken plastic, I use them. If they are properly installed, and the right size, they don't look out of place to me. I'm very careful with my dérailleur limit screws, but it's extra protection, so I have one on all my wheels. I've even acquired a small stash of spoke protectors since a few home mechanics I know save them for me.

The majority of riders I know that have thrown a chain into the spokes say their limit screws were properly adjusted.

One of my bikes has a yellowed plastic spoke protector that says "28 tooth max". If I change my freewheel to a 34 tooth low gear, where do I find a nice, classy protector to accommodate? Are there thickness differences? How about axle/hug hole size?