what's this plastic thing ?
 

http://bikeforums.net/attachment.php...hmentid=312496

Just bought this used bike and found the plastic guard there, it's loose, is it broken or just the way it is ? What is it for anyways ?

It's to stop the chain jammimg between the cassette and the spokes (and damaging them) if it comes off. If your gears are correctly adjusted this shouldn't happen, so feel free to remove it.

It tends to wear and start to shift around given time. If for some reason you remove your cassette its a good time to get rid of it.

In hipster slang that's referred to as a "dork disk." I leave mine on to eliminate any danger of being associated with something that *might* be hip.

I know someone whose derailer arm worked its way through the spokes when he took a fall. I had a feeling he was wanting my dork disc for something or other.

is it always loose like this ?

Shouldn't be. Looks like one of the tabs might have broken.

You can use shear strength, creative ways, or the local bike shop to remove it. Before I bought a chain whip and lockring removal tool to remove the cassette (gears) I scored the plastic disk with a box cutter, and bent it along the score lines, it eventually gave way and I was able to remove it. You can also remove the cassette but that requires a chain whip and lockring removal tool ($12-15 investment from amazon) or the lbs who charges $10 to remove the cassette.

The advantage of buying them is that you'll then be able to change your cassette when necessary. :)

I'd recommend that you take the wheel to your LBS and have them remove the cassette and swap on a new spoke protector, taken from the bin of them that they've removed from other bikes. It's a good thing to have on your bike. Those who remove the spoke protector are mechanically inclined, and personally make sure that the rear derailleur is maintained in proper adjustment.

Do a google search on "rear derailleur in spokes"...

Just cut it off with some snips, takes 10 seconds.

Hi,

Or just push back into place so its concentric.

rgds, sreten.

It was called a dork disk when hipsters were still but a gleam in their hippy dippy parents eyes.

I like the chromed metal ones on nicer vintage bikes, sort of art deco. The dirty plastic ones are hideous.


http://www.ebay.com/itm/Vintage-Chro...item416ac58fe0

Burn it off. Or not, I left mine on and it's not hurting anything.

@-@ i don't know if this was a troll's story, but someone apparently tried to burn his off and it burned the grease packed in his hubs.. Seems possible.

I'm sure that's happened, and it'll make a mess even if you don't torch the bearings.

And smell really pleasant too. Sorry, I guess I didn't include the sarcasm smiley last time.

Years ago, in Mountain Bike Magazine, Uncle Knobby's column was asked about these things; Knobby replied that they were called "Big Wedgies", all bike shops stocked them, all you had to do was go there and ask for one...lol!

They are there to keep the chain from destroying the spokes, should the chain fall into them. I don't see, and never HAVE seen, one of those saving a derailleur.

i can dig that. i'm so unhip, spandex riders fear catching whatever it is i have.
i have an alien light, a new mexico plate, 2 dork discs, wear boots, and am
really ugly. had a gumby tied to my helmet once and those people could NOT
stand it.

Good Things
 

That Thing was a CPSC mandate from back in the 70's (We know that CPSC was/is the Fount of Cycle Maintenance Wisdom), we called them Pie Plates when they were sturdy chromed metal. Yours is an inferior ( if that makes any sense in this context) plastic variant that has failed in service, it must go.

They are the Answer to the Question That No One Asked. If your rear derailleur is adjusted properly it serves no function.

Go to your LBS and have it exorcised and your derailleur adjusted properly by a person, or better yet get the tools as referenced previously and learn to do it yourself in person.

Being able to properly maintain your equipment personally is "a good thing", not some ill conceived chunk of rotating plastic.
Several other Good Things like having gears that shift accurately, brakes that stop and tires that are not flat may follow.

Personally,

-Bandera

Chrome spoke protectors were/are sturdy, heavy and eye-catching but never vintage even if they are old.

but never vintage even if they are old.

Old is one of the definitions of vintage, we are not talking about grapes here.

Granted that popular usage of vintage often equates it with old.

When I was riding a borrowed bike a few weeks back I discovered that the RD wasn't adjusted correctly when I shifted into the granny gear during a climb and realised I'd lost drive. It turned out the chain had fallen off to the inside of the largest cassette sprocket. No dork disk, apparently no damage to the spokes. It may just because I was lucky enough to realise something was wrong good and early, but generally speaking if you're going into the granny gear the chances are you're not going to be going very fast.