This is about the mysterious circular, see-through piece of plastic between the spokes and the cassette. Bikes of all kinds and price ranges ship out with these things. Strangely enough, bicycles you see out on the streets and trails almost never have that component mounted. Weird, right? So, what is the plastic disc on the back wheel of a bike?

The plastic dish mounted between a bike’s cassette and the wheel is a spoke protector. It’s larger than the biggest cog on the cassette and mounts to the actual spokes. It’s there to prevent damage to the spokes and cassette in case the chain falls off due to over-shifting beyond the largest cog.

bicycle spoke guard dork disc
The plastic disc next to the cassette has many names from spoke guard to dork disc.

Now that we know what its official name and function are, let’s answer why hardly anyone seems to be using it. There’s a hint in the nickname it got from the cycling community.

Why is it called a dork disc?

Bike spoke guards got nicknamed “dork discs” because only inexperienced riders leave them on. They’re not really doing much and additionally also look bad aesthetically. Still, dork discs come on most new bikes, no matter the type of bicycle or price range. So it takes a little customizing effort to get it off.

Because most riders don’t want their bike’s looks ruined by this plastic disc and it’s so easy to remove, you rarely see it on bikes that are actually used. Apart from showroom floors, it’s mostly seen on commuter bikes that are more of a transportation vehicle than a hobbyist’s equipment.

What is the point of a dork disc?

A spoke guard stops the bike chain from falling off the cassette and getting caught in the spokes. Damage to the wheel, chain, cassette and crashes due to wheel lock can be the result. With correct shifter limits, this doesn’t happen. So, a dork disc is only really useful when gears are set up incorrectly.

So, when gearing is working properly, there’s no job for the dork disc to fulfill. Only when regular maintenance is neglected or shifter components get damaged it can help you in the worst case: the rear wheel locking up when the chain falls off and gets wedged between the wheel and cassette.

mountain bike locking rear wheel
Skidding the rear wheel is fun when done on purpose, but not so much when it happens by surprise. // Photo by Darcy Lawrey

Another benefit would be in some circumstances where the gears over-shift and the derailleur gets caught in the spoked because it moved too far.

Again, the spoke guard helps with damage mitigation, not with the source problem. Which begs the question …

Is a dork disc necessary?

bicycle cassette no dork disc
There is space between the largest cog on a cassette and the spokes. But a well-maintained bike will not drop the chain there. // Photo by Markus Spiske

Dork discs are not necessary or even particularly useful. They only help when gears are set up wrong, so the problem isn’t solved by installing a spoke guard. It just helps slightly in the worst-case scenario when the chain falls off the cassette. Relying on a dork disc, therefore, is a dork move.

Should you remove the spoke protector?

There are more reasons for removing a spoke guard than for using it. It’s only marginally useful but can be very irritating while riding and look unpleasant. In the end, removing a the dork disc is a personal preference.

That being said, it’s also not necessary to remove it. But it can definitely help make your bike quieter when removing unnecessary components. Especially loose-fitting plastic ones that move around on the wheel.

And here’s how you do it.

How do you get the plastic ring off a bike?

Removing the spoke guard is relatively easy. There are a couple of methods you can use. Which one applies to you depends on the type of dork disc and how the cassette can be removed. Removing a dork disc is a process that can be completed easily with a few basic tools and patience.

Each method will require you to remove the rear wheel. So be sure you know how to do that and reinstall it properly. Here are the three main methods:

1. Remove the cassette

This is the easiest one for most spoke guards and the only clean one for those, that can’t be opened. Depending on the cassette and hub, a cassette removal tool or chain whip may be necessary. Many modern mountain bike cassettes come off by just loosening a nut using a standard wrench or Allen key.

The disc comes off easily right after the cassette. Reassemble and install the wheel again. Done.

2. Unclip spoke guard, that’s closed with clips

Some rare discs disassemble into two parts or at least unclip in one spot remove easily. You may be able to to this without removing the whole wheel, but it’s easier to work on the wheel itself.

Even when opened, you’ll find it difficult to remove the disc in a space this tight. Bend or even break it if you want. Or cut it in two halves.

3. Cut off the disc using a box knife

Now for the brute force method. There’s always use for sharp knives and a little destruction. It may be difficult to reach the disc with a knife, however. Best done through the backside where the brake is mounted. It’s easy to scratch the cassette, so this method should only be your last resort.

bicycle spoke guard dork disc 1 e1671798860989 edited
This is a single-piece dork disc with only a hole in the middle and to clips attaching it to the spokes (which rattles a lot).

Cassette Spacer, the other plastic ring on a bike’s rear wheel

Another plastic disc that is often found on the back wheel of a bike is called a cassette spacer. It’s a small, circular piece of plastic that is placed between the cassette and the hub of the wheel. It’s not visible from the outside unless the wheel is taken off the bike and the cassette is removed.

Cassette spacers are used to ensure that the cassette is properly aligned with the freehub on the hub of the wheel. The freehub is the part of the hub that the cassette attaches to, and it has a series of splines that the cassette’s cogs fit onto. The cassette spacer helps to align these splines and prevent the cassette from becoming misaligned as it rotates.

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