What is this plastic ring that is behind my cassette? it is wobbling around now and making noise. Can I just take it off?
What is this plastic ring that is behind my cassette? it is wobbling around now and making noise. Can I just take it off?
it is to reduce the chance of your chain/derailleur going into your spokes.
generally considered unfashionable to leave it on, so yes you can remove it. make sure your derailleur is properly adjusted!
What is this plastic ring that is behind my cassette? it is wobbling around now and making noise. Can I just take it off?
It’s a spoke protector, aka pie plate. It’s job is to make sure your chain does not derail off the high side of the biggest cog and jam between your cassette and your spokes. Yes you can remove it and most riders do remove them. Just make sure you keep your rear derailleur well adjusted so you don’t drop your chain into your spokes which in addition to forcing you off your bike to fix the problem can notch up and weaken your spokes.
-Dave
Jack quicker on the keys once again 
^^^^ what he said
What is this plastic ring that is behind my cassette? it is wobbling around now and making noise. Can I just take it off?
It’s official name is a “Dork Disk.”
Here is what real bikers have to say about it:
Do you think it might have a tiny bit of a “disk” effect?
Do you think it might have a tiny bit of a “disk” effect?
it might!
Hello jackmott and All,
How big could it get and still be legal? ie. not a disk cover?
How should it be shaped so as not to create poor airflow and should a matching ‘plastic ring’ be installed on the opposite side for balance?
Cheers,
Neal
+1 mph Faster