What is the plastic disc (8 inches diameter?) between the spokes and rear gears for, and can I do without one?
Submitted by admin on May 4, 2009 – 12:15 am9 Comments
Gene K asked:
I have a mountain bike from around 1992 or so, and the clear plastic disc between the spokes and the chain has slowly broken and in spite of my efforts, it finally cracked through and fell off. Should I bother replacing it, and is it difficult to do, requiring special tools? I assume I’d have to take off the cassette, so that might be a problem. I don’t have much in the way of bike tools.
The function of the plastic disc is to keep debris (i.e. sticks) from getting stuck in between your gears and the spokes of the wheel and bending your spokes. Having sticks stuck in your spokes can also throw your gears out of alignment and bring you to a very quick stop. (It will hurt). Despite all this, you can use your bike without the disc.
It is to prevent the chain from falling off your largest cog in the back and getting stuck between the spokes and your gears. With a properly adjusted dérailleur, you will never need it. It just adds weight and looks dorky.
Just remove your cassette (or freewheel) and slide that plastic bit out.
It’s a spoke protector. Most serious riders take them off anyway. Serious dork factor. You can just brake it off no problem. Just keep your drive train adjusted.
It’s to keep the rear derailleur from going into your spokes. My road bikes came with them and I simply took them off. If your bike is tuned properly, you don’t need it. Like the last post stated, it looks dorky!!
I can not speak for anyone else, but every time I get a new bike, that is one of the first things I take off. I have never had an issue with in not being on there.
it just keeps the chain from skipping off gear one and falling near the spokes, if you have a good quality bike you can do without it. i race a specialized hard rock(very durable bike by the way) and having that on their is just an annoyance so i cut it off about 3 months ago and haven’t had any problems with chain at all
It is to make your bike look really cool. You should also add some of the neon plastic spoke sliders.
It is indeed to keep your chain from riding over the last sprocket into the spokes.
I once had a bike shop tune my bike, and they removed the disk. Alas, they also adjusted my deraillier (sp?) and the first time I shifted into my lowest gear, the chain shifted over and into the spokes. It destroyed the wheel. Thus, it may look dorky, but unless you keep an eye on your drivetrain and take the time to adjust it, this little plastic disk is decent cheap insurance.
The plastic disc may look dorky or may seem to have no significance in terms of function. But may I give you a little bit of a background about this bike “component”. Back in the 90s, indexed shifting wasn’t very common and the shifters weren’t really that good because they relied on friction and some clicking mechanism to hold the shift lever in place. The plastic disc was for prevention of getting the chain between the largest cog and the spokes. Due to not-so-precise shifters/deraileurs, overshifting past the largest cog was common. This meant that you alwayus run the risk of ruining your wheel or the drivetrain if you didn’t have the plastic disc installed. Even if you adjusted your rear deraileur’s limiting screws often, overshifting wasn’t completely eliminated,thus the need for the “anti-chain-wedge” plastic disc.
Nowadays, with super-precise and reliable drivetrain components, there’s no more need for a plastic disc between the cogs and the spokes. Simply have your rear deraileur’s limiting screws adjusted properly and you’ll never have to worry about overshooting the granny cog again.
The issue of dorky-ness is up for debate. Not everyone finds the plastic wheel dorky.Likewise, not everyone gets bothered by the disc’s extra weight. If it’s broke, take it off and never replace it. If it’s new, but it looks like it traps a lot of dirt and grime, take it off. If you want the extra peace of mind that your chain wont be ****** in between the cogs and the spokes, then let it stay till its thrashed.
Safe riding!